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ABOUT THE TUTORIAL

Hibernate Tutorial

Hibernate is a high-performance Object/Relational persistence and query service which is licensed under the

open source GNU Lesser General Public License (LGPL) and is free to download. Hibernate not only takes care

of the mapping from Java classes to database tables (and from Java data types to SQL data types), but alsoprovides data query and retrieval facilities.

This tutorial will teach you how to use Hibernate to develop your database based web applications in simple andeasy steps.

Audience

This tutorial is designed for Java programmers with a need to understand the Hibernate framework and API. Aftercompleting this tutorial you will find yourself at a moderate level of expertise in using Hibernate from where youcan take yourself to next levels.

PrerequisitesWe assume you have good understanding of the Java programming language. A basic understanding of relationaldatabases, JDBC and SQL is very helpful.

Copyright & Disclaimer Notice

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tutorialspoint.com or this tutorial may not be redistributed or reproduced in any way, shape, or formwithout the written permission of tutorialspoint.com. Failure to do so is a violation of copyright laws.

This tutorial may contain inaccuracies or errors and tutorialspoint provides no guarantee regarding theaccuracy of the site or its contents including this tutorial. If you discover that the tutorialspoint.com siteor this tutorial content contains some errors, please contact us at [email protected]

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Table of ContentHibernate Tutorial.......................................................................2

Audience....................................................................................2Prerequisites..............................................................................2

Copyright & Disclaimer Notice...................................................2

ORM Overview..........................................................................8Pros and Cons of JDBC.................................................................. 8

Why Object elational !apping "O!#$........................................8

What is O!$................................................................................9

Ja%a O! &rame'or(s.................................................................10

Hibernate Overview.................................................................11

)ibernate *d%antages.................................................................11S+pported Databases..................................................................12

S+pported ,echnologies.............................................................. 12

Hibernate Architecture.............................................................13Con-g+ration Object................................................................... 14

Session&actory Object.................................................................14

Session Object............................................................................ 15

,ransaction Object...................................................................... 15

+ery Object...............................................................................15

Criteria Object.............................................................................15

Hibernate Environment............................................................16Do'nloading )ibernate/..............................................................16

0nstalling )ibernate.....................................................................1

)ibernate Prere1+isites...............................................................1

Hibernate !on"i#uration...........................................................18)ibernate Properties................................................................... 18

)ibernate 'ith !ySL Database.................................................19

Hibernate $e%%ion%..................................................................21Session 0nterface !ethods.......................................................... 22

Hibernate &er%i%tent !'a%%......................................................24

* simple POJO e2ample/..............................................................24

Hibernate Ma((in# )i'e%..........................................................26Hibernate Ma((in# *+(e%........................................................29Primiti%e types............................................................................ 29

Date and time types................................................................... 29

Binary and large object types..................................................... 30

JD34related types.........................................................................30

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Hibernate E,am('e%................................................................31Create POJO Classes....................................................................31

Create Database ,ables.............................................................. 32

Create !apping Con-g+ration &ile.............................................. 32

Create *pplication Class............................................................. 33

Compilation and E2ec+tion......................................................... 35

Hibernate O-R Ma((in#...........................................................36

Collections Mappings.............................................................................36

)ibernate Set !appings..............................................................36

De-ne DB!S ,ables...................................................................................... 3

De-ne POJO Classes........................................................................................3

De-ne )ibernate !apping &ile........................................................................39

Create *pplication Class.................................................................................40

Compilation and E2ec+tion..............................................................................42)ibernate SortedSet !appings................................................... 43

De-ne DB!S ,ables...................................................................................... 43




Compilation and E2ec+tion..............................................................................49

)ibernate List !appings............................................................. 50

De-ne DB!S ,ables...................................................................................... 50


De-ne )ibernate !apping &ile........................................................................52Create *pplication Class.................................................................................53


)ibernate Bag !appings.............................................................5

De-ne DB!S ,ables...................................................................................... 5





)ibernate !ap !appings............................................................ 63

De-ne DB!S ,ables...................................................................................... 63De-ne POJO Classes........................................................................................63




)ibernate Sorted!ap !appings..................................................69

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De-ne DB!S ,ables...................................................................................... 69




Association Mappings............................................................................76

)ibernate !any4to4One !appings...............................................6

De-ne DB!S ,ables...................................................................................... 6

De-ne POJO Classes........................................................................................



)ibernate One4to4One !appings.................................................83

De-ne DB!S ,ables...................................................................................... 83




)ibernate One4to4!any !appings...............................................90

De-ne DB!S ,ables...................................................................................... 90





)ibernate !any4to4!any !appings............................................96

De-ne DB!S ,ables...................................................................................... 9



Create *pplication Class.........................................................100

Compilation and E2ec+tion.....................................................102

Component !appings................................................................103

)ibernate Component !appings............................................... 103

De-ne DB!S ,ables..............................................................103

De-ne POJO Classes...............................................................104

De-ne )ibernate !apping &ile................................................106

Create *pplication Class.........................................................10

Compilation and E2ec+tion.....................................................109

Hibernate Annotation%...........................................................111En%ironment Set+p for )ibernate *nnotation............................111

*nnotated Class E2ample..........................................................111

5Entity *nnotation................................................................... 112

5,able *nnotation.....................................................................113

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50d and 56enerated7al+e *nnotations....................................113

5Col+mn *nnotation.................................................................113

Create *pplication Class............................................................113

Database Con-g+ration.............................................................115

Compilation and E2ec+tion........................................................116

Hibernate uer+ /an#ua#e...................................................11&O! Cla+se............................................................................. 11

*S Cla+se.................................................................................. 11

SELEC, Cla+se...........................................................................118

W)EE Cla+se...........................................................................118

ODE B8 Cla+se...................................................................... 118

6O9P B8 Cla+se...................................................................... 118

9sing :amed Paramters............................................................119

9PD*,E Cla+se.......................................................................... 119

DELE,E Cla+se.......................................................................... 119

0:SE, Cla+se........................................................................... 119

*ggregate !ethods................................................................... 119

Pagination +sing +ery............................................................. 120

Hibernate !riteria uerie%.....................................................121estrictions 'ith Criteria........................................................... 121

Pagination +sing Criteria........................................................... 122

Sorting the es+lts.................................................................... 123

Projections ; *ggregations....................................................... 123

Criteria +eries E2ample...........................................................123


Hibernate ative $/............................................................128Scalar 1+eries............................................................................128

Entity 1+eries............................................................................ 128

:amed SL 1+eries...................................................................129

:ati%e SL E2ample.................................................................. 129


Hibernate !achin#.................................................................133&irst4le%el cache.........................................................................133

Second4le%el cache....................................................................134+ery4le%el cache......................................................................134

,he Second Le%el Cache............................................................134

Conc+rrency strategies..............................................................134

Cache pro%ider.......................................................................... 135

,he +ery4le%el Cache.............................................................. 13

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Hibernate atch &roce%%in#..................................................138Batch Processing E2ample.........................................................139


Hibernate nterce(tor%...........................................................143)o' to +se 0nterceptors$...........................................................144

Create 0nterceptors....................................................................144

Create POJO Classes.................................................................. 145

Create Database ,ables.............................................................145

Create !apping Con-g+ration &ile............................................146

Create *pplication Class............................................................146


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HAPTER

1

ORM Overview

JDBC stands for

Java Database Connectivity

and provides a set of Java API for accessing the relational

databases from Java program. These Java APIs enables Java programs to execute SQL statements and interactwith any SQL compliant database.

JDBC provides a flexible architecture to write a database independent application that can run on differentplatforms and interact with different DBMS without any modification.

Pros and Cons of JDBCPros of JDBC Cons of JDBC

Clean and simple SQL processing Complex if it is used in large projects

Good performance with large data Large programming overhead

Very good for small applications No encapsulation

Simple syntax so easy to learn Hard to implement MVC concept

Query is DBMS specific

Why Object elational !apping "O!#$

When we work with an object-oriented systems, there's a mismatch between the object model and the relational

database. RDBMSs represent data in a tabular format whereas object-oriented languages, such as Java or C#represent it as an interconnected graph of objects. Consider the following Java Class with proper constructors and

associated public function:

public class Employee { private int id;

private String first_name;private String last_name;private int salary;

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public Employee() {}

public Employee(String fname, String lname, int salary) {this.first_name fname;

this.last_name lname;this.salary salary;

}

public int get!d() {return id;

}

public String get"irst#ame() {return first_name;

}

public String get$ast#ame() {return last_name;

}

public int getSalary() {return salary;

}}

Consider above objects need to be stored and retrieved into the following RDBMS table:

create table E%&$'EE (id !# #' #*$$ auto_increment,first_name +-/-(01) default #*$$,last_name +-/-(01) default #*$$,salary !# default #*$$,

&-!%- 2E (id));

First problem, what if we need to modify the design of our database after having developed few pages or ourapplication? Second, Loading and storing objects in a relational database exposes us to the following fivemismatch problems.

Mismatch Description

Granularity Sometimes you will have an object model which has more classes than thenumber of corresponding tables in the database.

Inheritance RDBMSs do not define anything similar to Inheritance which is a natural paradigm

in object-oriented programming languages.

Identity A RDBMS defines exactly one notion of 'sameness': the primary key. Java,

however, defines both object identity (a==b) and object equality (a.equals(b)).

Associations Object-oriented languages represent associations using object references where

as am RDBMS represents an association as a foreign key column.

Navigation The ways you access objects in Java and in a RDBMS are fundamentally different.

TheObject-RelationalMapping (ORM) is the solution to handle all the above impedance mismatches.

What is O!$

ORM stands forObject-RelationalMapping (ORM) is a programming technique for converting data between

relational databases and object oriented programming languages such as Java, C# etc. An ORM system hasfollowing advantages over plain JDBC

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S.N.Advantages

1 Lets business code access objects rather than DB tables.

2 Hides details of SQL queries from OO logic.

3 Based on JDBC 'under the hood'

4 No need to deal with the database implementation.

5 Entities based on business concepts rather than database structure.

6 Transaction management and automatic key generation.

7 Fast development of application.

An ORM solution consists of the following four entities:

S.N.Solutions

1 An API to perform basic CRUD operations on objects of persistent classes.2 A language or API to specify queries that refer to classes and properties of classes.

3 A configurable facility for specifying mapping metadata.

4 A technique to interact with transactional objects to perform dirty checking, lazy association fetching, andother optimization functions.

Ja%a O! &rame'or(s

There are several persistent frameworks and ORM options in Java. A persistent framework is an ORM service thatstores and retrieves objects into a relational database.

Enterprise JavaBeans Entity Beans

Java Data Objects

Castor

TopLink

Spring DAO

Hibernate

And many more

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HAPTER

2

Hibernate Overview

Hibernate is an Object-Relational Mapping(ORM) solution for JAVA and it raised as an open source

persistent framework created by Gavin King in 2001. It is a powerful, high performance Object-RelationalPersistence and Query service for any Java Application.

Hibernate maps Java classes to database tables and from Java data types to SQL data types and relieve thedeveloper from 95% of common data persistence related programming tasks.

Hibernate sits between traditional Java objects and database server to handle all the work in persisting thoseobjects based on the appropriate O/R mechanisms and patterns.

)ibernate *d%antages

Hibernate takes care of mapping Java classes to database tables using XML files and without writing anyline of code.

Provides simple APIs for storing and retrieving Java objects directly to and from the database.

If there is change in Database or in any table then the only need to change XML file properties.

Abstract away the unfamiliar SQL types and provide us to work around familiar Java Objects.

Hibernate does not require an application server to operate.

Manipulates Complex associations of objects of your database.


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Minimize database access with smart fetching strategies.

Provides Simple querying of data.

S+pported DatabasesHibernate supports almost all the major RDBMS. Following is list of few of the database engines supported byHibernate.

HSQL Database Engine

DB2/NT

MySQL

PostgreSQL

FrontBase

Oracle

Microsoft SQL Server Database

Sybase SQL Server

Informix Dynamic Server

S+pported ,echnologiesHibernate supports a variety of other technologies, including the following:

XDoclet Spring

J2EE

Eclipse plug-ins

Maven


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HAPTER

3

Hibernate Architecture

The Hibernate architecture is layered to keep you isolated from having to know the underlying APIs.

Hibernate makes use of the database and configuration data to provide persistence services (and persistentobjects) to the application.

Following is a very high level view of the Hibernate Application Architecture.

Following is a detailed view of the Hibernate Application Architecture with few important core classes.

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Hibernate uses various existing Java APIs, like JDBC, Java Transaction API(JTA), and Java Naming and DirectoryInterface (JNDI). JDBC provides a rudimentary level of abstraction of functionality common to relationaldatabases, allowing almost any database with a JDBC driver to be supported by Hibernate. JNDI and JTA allowHibernate to be integrated with J2EE application servers.

Following section gives brief description of each of the class objects involved in Hibernate ApplicationArchitecture.

Con-g+ration Object

The Configuration object is the first Hibernate object you create in any Hibernate application and usually createdonly once during application initialization. It represents a configuration or properties file required by the Hibernate.The Configuration object provides two keys components:

Database Connection:This is handled through one or more configuration files supported by Hibernate.These files arehibernate.properties andhibernate.cfg.xml.

Class Mapping Setup:This component creates the connection between the Java classes and databasetables.

Session&actory Object

Configuration object is used to create aSessionFactory object which inturn configures Hibernate for theapplication using the supplied configuration file and allows for a Session object to be instantiated. TheSessionFactoryis a thread safe object and used by all the threads of an application.

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TheSessionFactory is heavyweight object so usually it is created during application start up and kept for lateruse. You would need oneSessionFactory object per database using a separate configuration file. So if you areusing multiple databases then you would have to create multipleSessionFactory objects.

Session ObjectA Session is used to get a physical connection with a database. The Session object is lightweight and designed tobe instantiated each time an interaction is needed with the database. Persistent objects are saved and retrievedthrough a Session object.

The session objects should not be kept open for a long time because they are not usually thread safe and theyshould be created and destroyed them as needed.

,ransaction Object

A Transaction represents a unit of work with the database and most of the RDBMS supports transaction

functionality. Transactions in Hibernate are handled by an underlying transaction manager and transaction (fromJDBC or JTA).

This is an optional object and Hibernate applications may choose not to use this interface, instead managingtransactions in their own application code.

+ery Object

Query objects use SQL or Hibernate Query Language (HQL) string to retrieve data from the database and createobjects. A Query instance is used to bind query parameters, limit the number of results returned by the query, andfinally to execute the query.

Criteria ObjectCriteria object are used to create and execute object oriented criteria queries to retrieve objects.

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HAPTER

4

Hibernate Environment

This chapter will explain how to install Hibernate and other associated packages to prepare a develop

environment for the Hibernate applications. We will work with MySQL database to experiment with Hibernateexamples, so make sure you already have setup for MySQL database. For a more detail on MySQL you cancheck our MySQL Tutorial .

Do'nloading )ibernate/

It is assumed that you already have latest version of Java is installed on your machine. Following are the simplesteps to download and install Hibernate on your machine.

Make a choice whether you want to install Hibernate on Windows, or Unix and then proceed to the next

step to download .zip file for windows and .tz file for Unix.

Download the latest version of Hibernate from http://www.hibernate.org/downloads.

At the time of writing this tutorial I downloadedhibernate-distribution-3.6.4.Final and when you unzipthe downloaded file it will give you directory structure as follows.

http://www.tutorialspoint.com/mysql/index.htmhttp://www.tutorialspoint.com/mysql/index.htmhttp://www.tutorialspoint.com/mysql/index.htmhttp://www.tutorialspoint.com/mysql/index.htmhttp://www.hibernate.org/downloadshttp://www.hibernate.org/downloadshttp://www.hibernate.org/downloadshttp://www.tutorialspoint.com/mysql/index.htmhttp://www.hibernate.org/downloads


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0nstalling )ibernate

Once you downloaded and unzipped the latest version of the Hibernate Installation file, you need to performfollowing two simple steps. Make sure you are setting your CLASSPATH variable properly otherwise you will faceproblem while compiling your application.

Now copy all the library files from /lib into your CLASSPATH, and change your classpath variable toinclude all the JARs:

Finally copyhibernate3.jar file into your CLASSPATH. This file lies in the root directory of the installationand is the primary JAR that Hibernate needs to do its work.

)ibernate Prere1+isites

Following is the list of the packages/libraries required by Hibernate and you should install them before startingwith Hibernate. To install these packages you would have to copy library files from /lib into your CLASSPATH, andchange your CLASSPATH variable accordingly.

S.N. Packages/Libraries

1 dom4j- XML parsing www.dom4j.org/

2 Xalan- XSLT Processor http://xml.apache.org/xalan-j/

3 Xerces- The Xerces Java Parser http://xml.apache.org/xerces-j/

4 cglib- Appropriate changes to Java classes at runtime http://cglib.sourceforge.net/

5 log4j- Logging Faremwork http://logging.apache.org/log4j

6 Commons- Logging, Email etc. http://jakarta.apache.org/commons

7 SLF4J- Logging Facade for Java http://www.slf4j.org

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HAPTER

5

Hibernate onfiguration

Hibernate requires to know in advance where to find the mapping information that defines how your Java

classes relate to the database tables. Hibernate also requires a set of configuration settings related to databaseand other related parameters. All such information is usually supplied as a standard Java properties file calledhibernate.properties, or as an XML file namedhibernate.cfg.xml.

I will consider XML formatted filehibernate.cfg.xml to specify required Hibernate properties in my examples.

Most of the properties take their default values and it is not required to specify them in the property file unless it isreally required. This file is kept in the root directory of your application's classpath.

)ibernate Properties

Following is the list of important properties you would require to configure for a databases in a standalonesituation:

S.N.Properties and Description

1 hibernate.dialect

This property makes Hibernate generate the appropriate SQL for the chosen database.

2 hibernate.connection.driver_class

The JDBC driver class.

3 hibernate.connection.url

The JDBC URL to the database instance.

4 hibernate.connection.username

The database username.

5 hibernate.connection.password

The database password.6 hibernate.connection.pool_size

Limits the number of connections waiting in the Hibernate database connection pool.

7 hibernate.connection.autocommit

Allows autocommit mode to be used for the JDBC connection.

If you are using a database along with an application server and JNDI then you would have to configure thefollowing properties:

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S.N.Properties and Description

1 hibernate.connection.datasource

The JNDI name defined in the application server context you are using for the application.

2 hibernate.jndi.class

The InitialContext class for JNDI.

3 hibernate.jndi.Passes any JNDI property you like to the JNDIInitialContext.

4 hibernate.jndi.url

Provides the URL for JNDI.

5 hibernate.connection.username

The database username.

6 hibernate.connection.password

The database password.

)ibernate 'ith !ySL DatabaseMySQL is one of the most popular open-source database systems available today. Let uscreatehibernate.cfg.xml configuration file and place it in the root of your application's classpath. You would have

to make sure that you havetestdb database available in your MySQL database and you have a usertest

available to access the database.

The XML configuration file must conform to the Hibernate 3 Configuration DTD, which is available fromhttp://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd.

345ml version67.16 encoding6utf8964: 3


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The above configuration file includes tags which are related to hibernate-mapping file and we will see

in next chapter what exactly is a hibernate mapping file and how and why do we use it. Following is the list ofvarious important databases dialect property type:

Database Dialect Property

DB2 org.hibernate.dialect.DB2Dialect

HSQLDB org.hibernate.dialect.HSQLDialect

HypersonicSQL org.hibernate.dialect.HSQLDialect

Informix org.hibernate.dialect.InformixDialect

Ingres org.hibernate.dialect.IngresDialect

Interbase org.hibernate.dialect.InterbaseDialect

Microsoft SQL Server 2000 org.hibernate.dialect.SQLServerDialect

Microsoft SQL Server 2005 org.hibernate.dialect.SQLServer2005Dialect

Microsoft SQL Server 2008 org.hibernate.dialect.SQLServer2008Dialect

MySQL org.hibernate.dialect.MySQLDialect

Oracle (any version) org.hibernate.dialect.OracleDialect

Oracle 11g org.hibernate.dialect.Oracle10gDialect

Oracle 10g org.hibernate.dialect.Oracle10gDialect

Oracle 9i org.hibernate.dialect.Oracle9iDialect

PostgreSQL org.hibernate.dialect.PostgreSQLDialect

Progress org.hibernate.dialect.ProgressDialect

SAP DB org.hibernate.dialect.SAPDBDialect

Sybase org.hibernate.dialect.SybaseDialect

Sybase Anywhere org.hibernate.dialect.SybaseAnywhereDialect

Serial No Class Name Functionality

1 Assert A set of assert methods.

2 TestCase A test case defines the fixture to run multiple tests.

3 TestResult A TestResult collects the results of executing a

test case.

4 TestSuite A TestSuite is a Composite of Tests.

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HAPTER

Hibernate !e""ion"

ASession is used to get a physical connection with a database. The Session object is lightweight and

designed to be instantiated each time an interaction is needed with the database. Persistent objects are savedand retrieved through a Session object.

The session objects should not be kept open for a long time because they are not usually thread safe and theyshould be created and destroyed them as needed. The main function of the Session is to offer create, read anddelete operations for instances of mapped entity classes. Instances may exist in one of the following three statesat a given point in time:

transient:A new instance of a a persistent class which is not associated with a Session and has norepresentation in the database and no identifier value is considered transient by Hibernate.

persistent:You can make a transient instance persistent by associating it with a Session. A persistentinstance has a representation in the database, an identifier value and is associated with a Session.

detached:Once we close the Hibernate Session, the persistent instance will become a detachedinstance.

A Session instance is serializable if its persistent classes are serializable. A typical transaction should use thefollowing idiom:

Session session factory.openSession();ransaction t5 null;try {

t5 session.beginransaction();

>> do some ?or...t5.commit();

}catch (E5ception e) {

if (t5null) t5.rollbac(); e.printStacrace();

}finally {session.close();

}

If the Session throws an exception, the transaction must be rolled back and the session must be discarded.


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Session 0nterface !ethodsThere are number of methods provided by theSession interface but I'm going to list down few important methodsonly, which we will use in this tutorial. You can check Hibernate documentation for a complete list of methodsassociated withSession andSessionFactory.

S.N.Session Methods and Description

1 Transaction beginTransaction()

Begin a unit of work and return the associated Transaction object.

2 void cancelQuery()

Cancel the execution of the current query.

3 void clear()

Completely clear the session.

4 Connection close()

End the session by releasing the JDBC connection and cleaning up.

5 Criteria createCriteria(Class persistentClass)

Create a new Criteria instance, for the given entity class, or a superclass of an entity class.

6 Criteria createCriteria(String entityName)Create a new Criteria instance, for the given entity name.

7 Serializable getIdentifier(Object object)

Return the identifier value of the given entity as associated with this session.

8 Query createFilter(Object collection, String queryString)

Create a new instance of Query for the given collection and filter string.

9 Query createQuery(String queryString)

Create a new instance of Query for the given HQL query string.

10 SQLQuery createSQLQuery(String queryString)

Create a new instance of SQLQuery for the given SQL query string.

11 void delete(Object object)

Remove a persistent instance from the datastore.

12 void delete(String entityName, Object object)

Remove a persistent instance from the datastore.

Session get(String entityName, Serializable id)

13 Return the persistent instance of the given named entity with the given identifier, or null if

there is no such persistent instance.

14 SessionFactory getSessionFactory()

Get the session factory which created this session.

15 void refresh(Object object)

Re-read the state of the given instance from the underlying database.

16 Transaction getTransaction()

Get the Transaction instance associated with this session.

17 boolean isConnected()

Check if the session is currently connected.

18 boolean isDirty()Does this session contain any changes which must be synchronized with the database?

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19 boolean isOpen()

Check if the session is still open.

20 Serializable save(Object object)

Persist the given transient instance, first assigning a generated identifier.

21 void saveOrUpdate(Object object)

Either save(Object) or update(Object) the given instance.22 void update(Object object)

Update the persistent instance with the identifier of the given detached instance.

23 void update(String entityName, Object object)

Update the persistent instance with the identifier of the given detached instance.

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HAPTER

#

Hibernate Per"i"tent $a""

The entire concept of Hibernate is to take the values from Java class attributes and persist them to a

database table. A mapping document helps Hibernate in determining how to pull the values from the classes andmap them with table and associated fields.

Java classes whose objects or instances will be stored in database tables are called persistent classes in

Hibernate. Hibernate works best if these classes follow some simple rules, also known as the Plain Old Java

Object (POJO) programming model. There are following main rules of persistent classes, however, none of these

rules are hard requirements.

All Java classes that will be persisted need a default constructor.

All classes should contain an ID in order to allow easy identification of your objects within Hibernate andthe database. This property maps to the primary key column of a database table.

All attributes that will be persisted should be declared private and havegetXXX andsetXXXmethodsdefined in the JavaBean style.

A central feature of Hibernate, proxies, depends upon the persistent class being either non-final, or theimplementation of an interface that declares all public methods.

All classes that do not extend or implement some specialized classes and interfaces required by the EJBframework.

The POJO name is used to emphasize that a given object is an ordinary Java Object, not a special object, and in

particular not an Enterprise JavaBean.

* simple POJO e2ample/

Based on the few rules mentioned above we can define a POJO class as follows:


private String first#ame;private String last#ame;private int salary;



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public Employee(String fname, String lname, int salary) {this.first#ame fname;

this.last#ame lname;this.salary salary;

}

public int get!d() {return id;}

public void set!d( int id ) {this.id id;

}

public String get"irst#ame() {return first#ame;

}

public void set"irst#ame( String first_name ) {this.first#ame first_name;

}

public String get$ast#ame() {return last#ame;

}

public void set$ast#ame( String last_name ) {

this.last#ame last_name;}


}

public void setSalary( int salary ) {this.salary salary;

}}

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HAPTER

%

Hibernate Ma&&ing 'i$e"

An Object/relational mappings are usually defined in an XML document. This mapping file instructs

Hibernate how to map the defined class or classes to the database tables.

Though many Hibernate users choose to write the XML by hand, a number of tools exist to generate the mappingdocument. These includeXDoclet, Middlegen andAndroMDA for advanced Hibernate users.

Let us consider our previously defined POJO class whose objects will persist in the table defined in next section.






}


}


}


}


}


}

public void set$ast#ame( String last_name ) {this.last#ame last_name;

}


}

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}}

There would be one table corresponding to each object you are willing to provide persistence. Consider aboveobjects need to be stored and retrieved into the following RDBMS table:

create table E%&$'EE (id !# #' #*$$ auto_increment,first_name +-/-(01) default #*$$,last_name +-/-(01) default #*$$,salary !# default #*$$,&-!%- 2E (id)

);

Based on the two above entities we can define following mapping file which instructs Hibernate how to map thedefined class or classes to the database tables.

345ml version67.16 encoding6utf8964: 3meta:

3id name6id6 type6int6 column6id6:3generator class6native6>:

3>id:

3property name6first#ame6 column6first_name6 type6string6>:3property name6last#ame6 column6last_name6 type6string6>:3property name6salary6 column6salary6 type6int6>:

3>class:3>hibernate8mapping:

You should save the mapping document in a file with the format .hbm.xml. We saved our mappingdocument in the file Employee.hbm.xml. Let us see little detail about the mapping elements used in the mappingfile:

The mapping document is an XML document having as the root element whichcontains all the elements.

The elements are used to define specific mappings from a Java classes to the database tables.The Java class name is specified using thename attribute of the class element and the database tablename is specified using thetable attribute.

The element is optional element and can be used to create the class description.

The element maps the unique ID attribute in class to the primary key of the database table.

Thename attribute of the id element refers to the property in the class and thecolumn attribute refers to

the column in the database table. Thetype attribute holds the hibernate mapping type, this mapping

types will convert from Java to SQL data type.

The element within the id element is used to automatically generate the primary keyvalues. Set theclass attribute of the generator element is set tonative to let hibernate pick up

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eitheridentity, sequence orhilo algorithm to create primary key depending upon the capabilities of the

underlying database.

The element is used to map a Java class property to a column in the database table.

Thename attribute of the element refers to the property in the class and thecolumn attribute refers tothe column in the database table. Thetype attribute holds the hibernate mapping type, this mapping


There are other attributes and elements available which will be used in a mapping document and I would try tocover as many as possible while discussing other Hibernate related topics.

TUTORIALS POINT


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HAPTER

.

(

Hibernate Ma&&ing T)&e"

When you prepare a Hibernate mapping document, we have seen that you map Java data types into

RDBMS data types. Thetypes declared and used in the mapping files are not Java data types; they are not SQL

database types either. These types are called Hibernate mapping types, which can translate from Java to SQLdata types and vice versa.

This chapter lists down all the basic, date and time, large object, and various other built-in mapping types.

Primiti%e typesMapping type Java type ANSI SQL Type

integer int or java.lang.Integer INTEGER

long long or java.lang.Long BIGINT

short short or java.lang.Short SMALLINT

float float or java.lang.Float FLOAT

double double or java.lang.Double DOUBLE

big_decimal java.math.BigDecimal NUMERIC

character java.lang.String CHAR(1)

string java.lang.String VARCHAR

byte byte or java.lang.Byte TINYINT

boolean boolean or java.lang.Boolean BIT

yes/no boolean or java.lang.Boolean CHAR(1) ('Y' or'N')

true/false boolean or java.lang.Boolean CHAR(1) ('T' or

'F')

Date and time typesMapping type Java type ANSI SQL Type

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date java.util.Date or java.sql.Date DATE

time java.util.Date or java.sql.Time TIME

timestamp java.util.Date or java.sql.Timestamp TIMESTAMP

calendar java.util.Calendar TIMESTAMP

calendar_date java.util.Calendar DATE

Binary and large object typesMapping type Java type ANSI SQL Type

binary byte[] VARBINARY (or

BLOB)

text java.lang.String CLOB

serializable any Java class that implements java.io.Serializable VARBINARY (or

BLOB)

clob java.sql.Clob CLOB

blob java.sql.Blob BLOB

JD34related types

Mapping type Java type ANSI SQL Type

class java.lang.Class VARCHAR

locale java.util.Locale VARCHAR

timezone java.util.TimeZone VARCHAR

currency java.util.Currency VARCHAR

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HAPTER

1*

Hibernate E+am&$e"

Let us try an example of using Hibernate to provide Java persistence in a standalone application. We willgo through different steps involved in creating Java Application using Hibernate technology.

Create POJO ClassesThe first step in creating an application is to build the Java POJO class or classes, depending on the applicationthat will be persisted to the database. Let us consider ourEmployee class withgetXXX andsetXXX methods tomake it JavaBeans compliant class.

A POJO (Plain Old Java Object) is a Java object that doesn't extend or implement some specialized classes andinterfaces respectively required by the EJB framework. All normal Java objects are POJO.

When you design a classs to be persisted by Hibernate, it's important to provide JavaBeans compliant code aswell as one attribute which would work as index likeid attribute in the Employee class.






}


}public void set!d( int id ) {

this.id id;}


}


}public String get$ast#ame() {

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return last#ame;}


}

public int getSalary() {return salary;}


}}

Create Database ,ables

Second step would be creating tables in your database. There would be one table corresponding to each objectyou are willing to provide persistence. Consider above objects need to be stored and retrieved into the followingRDBMS table:


);

Create !apping Con-g+ration &ile

This step is to create a mapping file that instructs Hibernate how to map the defined class or classes to thedatabase tables.

345ml version67.16 encoding6utf8964:3meta:


3>id:

3property name6first#ame6 column6first_name6 type6string6>:3property name6last#ame6 column6last_name6 type6string6>:

3property name6salary6 column6salary6 type6int6>:3>class:

3>hibernate8mapping:

You should save the mapping document in a file with the format .hbm.xml. We saved our mappingdocument in the file Employee.hbm.xml. Let us see little detail about the mapping document:

The mapping document is an XML document having as the root element whichcontains all the elements.

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The elements are used to define specific mappings from a Java classes to the database tables.The Java class name is specified using thename attribute of the class element and the database tablename is specified using thetable attribute.


The element maps the unique ID attribute in class to the primary key of the database table.

Thename attribute of the id element refers to the property in the class and thecolumn attribute refers to



The element within the id element is used to automatically generate the primary key

values. Set theclass attribute of the generator element is set tonative to let hibernate pick up

eitheridentity, sequence orhilo algorithm to create primary key depending upon the capabilities of the

underlying database.

The

element is used to map a Java class property to a column in the database table.Thename attribute of the element refers to the property in the class and thecolumn attribute refers to



There are other attributes and elements available which will be used in a mapping document and I would try tocover as many as possible while discussing other Hibernate related topics.

Create *pplication Class

Finally, we will create our application class with the main() method to run the application. We will use thisapplication to save few Employee's records and then we will apply CRUD operations on those records.

import Cava.util.$ist; import Cava.util.


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>K %E.deleteEmployee(emp!K $ist do?n ne? list of the employees K>%E.listEmployees();

}

>K %ethod to -EE an employee in the database K>public !nteger addEmployee(String fname, String lname, int salary)

{ Session session factory.openSession();

ransaction t5 null; !nteger employee!public void listEmployees( ){

Session session factory.openSession(); ransaction t5 null;try{


$ist employees session.createAuery(6"-'% Employee6).list();for (!terator iterator

employees.iterator(); iterator.has#e5t();){Employee employee (Employee) iterator.ne5t(); System.out.print(6"irst #ame= 6 I employee.get"irst#ame()); System.out.print(6 $ast #ame= 6 I employee.get$ast#ame()); System.out.println(6 Salary= 6 I employee.getSalary());

}t5.commit();

}catch (/ibernateE5ception e) {if (t5null) t5.rollbac();

e.printStacrace();}finally {session.close();

}}>K %ethod to *&

public void updateEmployee(!nteger Employee!


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try{

t5 session.beginransaction();Employee employee

(Employee)session.get(Employee.class, Employee!"irst #ame= Lara $ast #ame= li Salary= 7111"irst #ame=


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HAPTER

11

Hibernate O,R Ma&&ing

So far we have seen very basic O/R mapping using hibernate but there are three most important mappingtopics which we have to learn in detail. These are the mapping of collections, the mapping of associationsbetween entity classes and Component Mappings.

Collections MappingsIf an entity or class has collection of values for a particular variable, then we can map those values using any oneof the collection interfaces available in java. Hibernate can persist instances ofjava.util.Map, java.util.Set,java.util.SortedMap, java.util.SortedSet, java.util.List, and any arrayof persistent entities or values.

Collection type Mapping and Description

java.util.Set This is mapped with a element and initialized with java.util.HashSet

java.util.SortedSet This is mapped with a element and initialized with java.util.TreeSet.Thesort attribute can be set to either a comparator or natural ordering.

java.util.List This is mapped with a element and initialized with java.util.ArrayList

java.util.Collection This is mapped with a or element and initialized with

java.util.ArrayList

java.util.Map This is mapped with a element and initialized with java.util.HashMap

This is mapped with a element and initialized with java.util.SortedMap java.util.TreeMap. Thesort attribute can be set to either a comparator or

natural ordering.

Arrays are supported by Hibernate with for Java primitive value types and for everythingelse. However, they are rarely used so I'm not going to discuss them in this tutorial.

If you want to map a user defined collection interfaces which is not directly supported by Hibernate, you need totell Hibernate about the semantics of your custom collections which is not very easy and not recommend to beused.

)ibernate Set !appingsASet is a java collection that does not contain any duplicate element. More formally, sets contain no pair ofelements e1 and e2 such that e1.equals(e2), and at most one null element. So objects to be added to a set must

TUTORIALS POINT

http://www.tutorialspoint.com/hibernate/hibernate_set_mapping.htmhttp://www.tutorialspoint.com/hibernate/hibernate_sortedset_mapping.htmhttp://www.tutorialspoint.com/hibernate/hibernate_list_mapping.htmhttp://www.tutorialspoint.com/hibernate/hibernate_bag_mapping.htmhttp://www.tutorialspoint.com/hibernate/hibernate_map_mapping.htmhttp://www.tutorialspoint.com/hibernate/hibernate_sortedmap_mapping.htmhttp://www.tutorialspoint.com/hibernate/hibernate_set_mapping.htmhttp://www.tutorialspoint.com/hibernate/hibernate_sortedset_mapping.htmhttp://www.tutorialspoint.com/hibernate/hibernate_list_mapping.htmhttp://www.tutorialspoint.com/hibernate/hibernate_bag_mapping.htmhttp://www.tutorialspoint.com/hibernate/hibernate_map_mapping.htmhttp://www.tutorialspoint.com/hibernate/hibernate_sortedmap_mapping.htm


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return first#ame;}


}

public String get$ast#ame() {return last#ame;}


}


}


}

public Set getertificates() {return certificates;

}

public void setertificates( Set certificates ) {this.certificates certificates;

}}

Now let us define another POJO class corresponding to CERTIFICATE table so that certificate objects can bestored and retrieved into the CERTIFICATE table. This class should also implement both the equals() andhashCode() methods so that Java can determine whether any two elements/objects are identical.

public class ertificate {private int id; privateString name;

public ertificate() {}

public ertificate(String name){ this.name name;}

public int get!d(){ return id;

}


}

public String get#ame(){ return name;

}

public void set#ame( String name ){ this.name name;

}

public boolean eBuals('bCect obC){ if (obC null) return false;if (this.getlass().eBuals(obC.getlass())) return false;

ertificate obC0 (ertificate)obC;if((this.id obC0.get!d()) UU (this.name.eBuals(obC0.get#ame()))){

return true;}return false;

}

public int hashode(){ int tmp 1;tmp ( id I name ).hashode();

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return tmp;}

}

De-ne )ibernate !apping &ileLet us develop our mapping file which instructs Hibernate how to map the defined classes to the database tables.The element will be used to define the rule for Set collection used.


3id name6id6 type6int6 column6id6:

3generator class6native6>:3>id:

3set name6certificates6 cascade6all6:3ey column6employee_id6>: 3one8to8many class6ertificate6>:

3>set:


3>class:

3class name6ertificate6 table6E-!"!E6:3meta attribute6class8description6:

his class contains the certificaterecords. 3>meta:


3>id:

3property name6name6 column6certificate_name6 type6string6>:3>class:


You should save the mapping document in a file with the format .hbm.xml. We saved our mappingdocument in the file Employee.hbm.xml. You are already familiar with most of the mapping detail but let us see allthe elements of mapping file once again:

The mapping document is an XML document having as the root element whichcontains two elements corresponding to each class.

The elements are used to define specific mappings from a Java classes to the database tables. TheJava class name is specified using thename attribute of the class element and the database table name is

specified using thetable attribute.The element is optional element and can be used to create the class description.

The element maps the unique ID attribute in class to the primary key of the database table. Thename

attribute of the id element refers to the property in the class and thecolumn attribute refers to the column in

the database table. Thetype attribute holds the hibernate mapping type, this mapping types will convert fromJava to SQL data type.

The element within the id element is used to automatically generate the primary key values. Settheclass attribute of the generator element is set tonative to let hibernate pick up eitheridentity, sequenceor hiloalgorithm to create primary key depending upon the capabilities of the underlying database.

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The element is used to map a Java class property to a column in the database table. Thename

attribute of the element refers to the property in the class and thecolumn attribute refers to the column in thedatabase table. Thetype attribute holds the hibernate mapping type, this mapping types will convert from

Java to SQL data type.

The element is new here and has been introduced to set the relationship between Certificate andEmployee classes. We used thecascade attribute in the element to tell Hibernate to persist the

Certificate objects at the same time as the Employee objects. Thenameattribute is set to the definedSet

variable in the parent class, in our case it iscertificates. For each set variable, we need to define a separate

set element in the mapping file.

The element is the column in the CERTIFICATE table that holds the foreign key to the parent object ie.table EMPLOYEE.

The element indicates that one Employee object relates to many Certificate objects and, assuch, the Certificate object must have a Employee parent associated with it. You can use either,or elements based on your requirement.


Finally, we will create our application class with the main() method to run the application. We will use thisapplication to save few Employee's records alongwith their certificates and then we will apply CRUD operations onthose records.

import Cava.util.K;

import org.hibernate./ibernateE5ception; import org.hibernate.Session;

import org.hibernate.ransaction; importorg.hibernate.Session"actory; importorg.hibernate.cfg.onfiguration;

public class %anageEmployee {

private static Session"actory factory; public static void main(StringGH args) {

try{factory ne? onfiguration().configure().buildSession"actory(); }

catch (hro?able e5) {

System.err.println(6"ailed to create session"actory obCect.6 I e5);thro? ne? E5ception!n!nitialiJerError(e5);

}%anageEmployee %E ne? %anageEmployee();

>K $et us have a set of certificates for the first employee K>/ashSet set7 ne? /ashSet();

set7.add(ne? ertificate(6%6));set7.add(ne? ertificate(6%F6));set7.add(ne? ertificate(6&%&6));

>K dd employee records in the database K>!nteger emp!K nother set of certificates for the second employee K>/ashSet set0 ne? /ashSet();

set0.add(ne? ertificate(6F6)); set0.add(ne? ertificate(6F6));

>K dd another employee record in the database K>!nteger emp! %E.listEmployees();

>K *pdate employeeOs salary recordsK> %E.updateEmployee(emp!K

TUTORIALS POINT



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%E.deleteEmployee(emp!K $ist do?n all the employeesK> %E.listEmployees();

}

>K %ethod to add an employee record in the database K>public !nteger addEmployee(String fname, String lname,

int salary, Set cert){ Session session factory.openSession();




$ist employees session.createAuery(6"-'% Employee6).list();for (!terator iterator7

employees.iterator(); iterator7.has#e5t();){Employee employee (Employee) iterator7.ne5t(); System.out.print(6"irst #ame= 6 I employee.get"irst#ame()); System.out.print(6 $ast #ame= 6 I employee.get$ast#ame()); System.out.println(6 Salary= 6 I employee.getSalary()); Set

certificates employee.getertificates();for (!terator iterator0

certificates.iterator(); iterator0.has#e5t();){ertificate cert#ame (ertificate) iterator0.ne5t(); System.out.println(6ertificate= 6 I cert#ame.get#ame());

}}t5.commit();

}catch (/ibernateE5ception e) {if (t5null) t5.rollbac();e.printStacrace();


}}>K %ethod to update salary for an employee K>



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if (t5null) t5.rollbac();e.printStacrace();


}}

>K %ethod to delete an employee from the records K>public void deleteEmployee(!nteger Employee!


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ertificate= %

If you check your EMPLOYEE and CERTIFICATE tables, they should have following records:

mysBl: selectK from employee;

8888I I I I88888888I

S id S first_name S last_name salary 8888I 888888888888I 88888888888I88888888I I 7

M111

8888I 888888888888I 88888888888I88888888I I

7 ro? in set (1.11 sec)mysBl: selectKfromcer

tificate;I I 8888888888888I IS id S employee_id 8888I 888888888888888888I 8888888888888I I 7 7 0 7

@ 7 8888I 888888888888888888I 8888888888888I I@ ro?s

mysBl:

)ibernate SortedSet !appingsASortedSet is a java collection that does not contain any duplicate element and elements are ordered using theirnatural ordering or by a comparator provided.

A SortedSet is mapped with a element in the mapping table and initialized with java.util.TreeSet. Thesortattribute can be set to either a comparator or natural ordering. If we usenatural ordering then its iterator willtraverse the set in ascending element order.

De-ne DB!S ,ables

Consider a situation where we need to store our employee records in EMPLOYEE table which will have followingstructure:


);

Further, assume each employee can have one or more certificate associated with him/her. So we will storecertificate related information in a separate table which has following structure:

create table E-!"!E (

id !# #' #*$$ auto_increment, certificate_name +-/-(@1) default #*$$,employee_id !# default #*$$,&-!%- 2E (id)

);

There will beone-to-many relationship between EMPLOYEE and CERTIFICATE objects:

TUTORIALS POINT


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De-ne POJO ClassesLet us implement our POJO classEmployee which will be used to persist the objects related to EMPLOYEE tableand having a collection of certificates inSortedSet variable.

import Cava.util.K;


private String first#ame;private String last#ame;private int salary;private SortedSet certificates;




}


}


}


}


}


}

public void set$ast#ame( String last_name ) {this.last#ame last_name;}


}


}

public SortedSet getertificates() {return certificates;

}

public void setertificates( SortedSet certificates ) {this.certificates certificates;

}

}

Now let us define another POJO class corresponding to CERTIFICATE table so that certificate objects can bestored and retrieved into the CERTIFICATE table. This class should also implementComparable interface andcompareTo method which will be used to sort the elements in case you setsort="natural" in your mapping file

(see below mapping file).

public class ertificate implements omparable 3ertificate:{

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private int id; private String name;


public ertificate(String name)

{ this.name name;}


}


}

public String get#ame() {return name;

}

public void set#ame( String name ) {this.name name;

}

public int compareo(ertificate that){final int FE"'-E 87;

final int "E- 7;

if (that null){ return FE"'-E;

}

omparable thisertificate this.get#ame();omparable thatertificate that.get#ame();

if(thisertificate null){ return "E-;

} else if(thatertificate null){ return FE"'-E;

} else {return thisertificate.compareo(thatertificate);

}}

}

De-ne )ibernate !apping &ile

Let us develop our mapping file which instructs Hibernate how to map the defined classes to the database tables.The element will be used to define the rule for SortedSet collection used.



3>id:

3set name6certificates6 cascade6all6 sort6%ylass6:3ey column6employee_id6>:

TUTORIALS POINT



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3one8to8manyclass6ertificate6>: 3>set:


3>class:




3>id:

3property name6name6 column6certificate_name6 type6string6>:3>class:


You should save the mapping document in a file with the format .hbm.xml. We saved our mappingdocument in the file Employee.hbm.xml. You are already familiar with most of the mapping detail but let us see allthe elements of mapping file once again:

The mapping document is an XML document having as the root element whichcontains two elements corresponding to each class.

The elements are used to define specific mappings from a Java classes to the database tables. TheJava class name is specified using thename attribute of the class element and the database table name isspecified using thetable attribute.


The element maps the unique ID attribute in class to the primary key of the database table. Thename

attribute of the id element refers to the property in the class and thecolumn attribute refers to the column inthe database table. Thetype attribute holds the hibernate mapping type, this mapping types will convert fromJava to SQL data type.

The element within the id element is used to automatically generate the primary key values. Set

theclass attribute of the generator element is set tonative to let hibernate pick up eitheridentity, sequence

or hiloalgorithm to create primary key depending upon the capabilities of the underlying database.

The element is used to map a Java class property to a column in the database table.

Thename attribute of the element refers to the property in the class and thecolumn attribute refers to the

column in the database table. Thetype attribute holds the hibernate mapping type, this mapping types will

convert from Java to SQL data type.

The element is used to set the relationship between Certificate and Employee classes. We used

thecascade attribute in the element to tell Hibernate to persist the Certificate objects at the same time

as the Employee objects. Thename attribute is set to the definedSortedSet variable in the parent class, in

our case it iscertificates. Thesort attribute can be set tonatural to have natural sorting or it can be set to a

custom classimplementingjava.util.Comparator.Wehave used aclassMyClass which implements

java.util.Comparator to reverse the sorting order implemented inCertificate class.

The element is the column in the CERTIFICATE table that holds the foreign key to the parent object ie.table EMPLOYEE.

The element indicates that one Employee object relates to many Certificate objects and, assuch, the Certificate object must have a Employee parent associated with it. You can use either, or elements based on your requirement.

If we usesort="natural" setting then we do not need to create a separate class because Certificate class already

has implemented Comparable interface and hibernate will use compareTo() method defined in Certificate class to

compare certificate names. But we are using a custom comparator classMyClass in our mapping file so we would

have to create this class based on our sorting algorithm. Let us do descending sorting in this class using this

class.

import Cava.util.omparator;


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TUTORIALS POINT



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public class %ylass implementsomparator3ertificate:{ public int compare(ertificate o7, ertificate o0) {

final int FE"'-E 87;final int "E- 7;

>K o reverse the sorting order, multiple by 87 K>if (o0 null) {

return FE"'-E K 87;}

omparable thisertificate o7.get#ame();omparable thatertificate o0.get#ame();

if(thisertificate null){ return "E- K 7;

} else if(thatertificate null){ return FE"'-E K 87;

} else {return thisertificate.compareo(thatertificate) K 87;

}

}}


Finally, we will create our application class with the main() method to run the application. We will use thisapplication to save few Employee's records alongwith their certificates and then we will apply CRUD operations onthose records.

import Cava.util.K;

import org.hibernate./ibernateE5ception; import org.hibernate.Session;

import org.hibernate.ransaction; importorg.hibernate.Session"actory; import

org.hibernate.cfg.onfiguration;

public class %anageEmployee {

private static Session"actory factory; public static void main(StringGH args) {

try{

factory ne? onfiguration().configure().buildSession"actory(); }catch (hro?able e5) {

System.err.println(6"ailed to create session"actory obCect.6 I e5);thro? ne? E5ception!n!nitialiJerError(e5);

}%anageEmployee %E ne? %anageEmployee();

>K $et us have a set of certificates for the first employee K>reeSet set7 ne? reeSet();

set7.add(ne? ertificate(6%6));set7.add(ne? ertificate(6%F6));set7.add(ne? ertificate(6&%&6));

>K dd employee records in the database K>!nteger emp!K nother set of certificates for the second employee K>reeSet set0 ne? reeSet();

set0.add(ne? ertificate(6F6)); set0.add(ne? ertificate(6F6));

>K dd another employee record in the database K>!nteger emp!


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>K $ist do?n all the employeesK> %E.listEmployees();

>K *pdate employeeOs salary recordsK> %E.updateEmployee(emp!K %E.deleteEmployee(emp!K $ist do?n all the employeesK> %E.listEmployees();

}

>K %ethod to add an employee record in the database K>public !nteger addEmployee(String fname, String lname,

int salary, SortedSet cert){ Session session factory.openSession();




$ist employees session.createAuery(6"-'% Employee6).list();for (!terator iterator7

employees.iterator(); iterator7.has#e5t();){Employee employee (Employee) iterator7.ne5t(); System.out.print(6"irst #ame= 6 I employee.get"irst#ame()); System.out.print(6 $ast #ame= 6 I employee.get$ast#ame()); System.out.println(6 Salary= 6 I employee.getSalary()); SortedSet certificates employee.getertificates();for (!terator iterator0

certificates.iterator(); iterator0.has#e5t();){ertificate cert#ame (ertificate) iterator0.ne5t(); System.out.println(6ertificate= 6 I cert#ame.get#ame());

}}t5.commit();

}catch (/ibernateE5ception e) {if (t5null) t5.rollbac();e.printStacrace();


}}>K %ethod to update salary for an employee K>



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t5 session.beginransaction();Employee employee

(Employee)session.get(Employee.class, Employee!K %ethod to delete an employee from the records K>public void deleteEmployee(!nteger Employee!


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ertificate= %F"irst #ame=


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Further, assume each employee can have one or more certificate associated with him/her. A List collectionmapping needs an index column in the collection table. The index column defines the position of the element inthe collection. So we will store certificate related information in a separate table which has following structure:

create table E-!"!E (

id !# #' #*$$ auto_increment, certificate_name +-/-(@1) default #*$$,id5 !# default #*$$,

employee_id !# default #*$$,&-!%- 2E (id)

);

There will beone-to-many relationship between EMPLOYEE and CERTIFICATE objects.

De-ne POJO ClassesLet us implement a POJO classEmployee which will be used to persist the objects related to EMPLOYEE tableand having a collection of certificates inList variable.

import Cava.util.K;


private String first#ame; private String last#ame; private int salary; private $ist certificates;




}


}


}


}


}


}


}public int getSalary() {

return salary;}


}

public $ist getertificates() {return certificates;

TUTORIALS POINT



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}

public void setertificates( $ist certificates ) {this.certificates certificates;

}}

We need to define another POJO class corresponding to CERTIFICATE table so that certificate objects can bestored and retrieved into the CERTIFICATE table.

public class ertificate{private int id; private String name;


public ertificate(String name){ this.name name;

}


}


}

public String get#ame() {return name;

}

public void set#ame( String name ) {this.name name;

}}

De-ne )ibernate !apping &ile

Let us develop our mapping file which instructs Hibernate how to map the defined classes to the database tables.The element will be used to define the rule for List collection used. The index of list is always of type integerand is mapped using the element.



3>id:3list name6certificates6 cascade6all6:

3ey column6employee_id6>: 3list8inde5 column6id56>: 3one8to8manyclass6ertificate6>:

3>list:


3>class:

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3>id:3property name6name6 column6certificate_name6 type6string6>:

3>class:


You should save the mapping document in a file with the format .hbm.xml. We saved our mappingdocument in the file Employee.hbm.xml. You are already famili

hibernate tutorial3

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