steps for ejb

7/30/2019 Steps for EJB

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The following steps are for Netbeans 6.5.1.

Pre-requisites: MySQL should be already installed. Incase of any problems,

contact Moses sir

1) Open Netbeans.2) File-> new Project -> Java EE -> Enterprise Application

JSP Servlet Session

Bean

Entity Bean

Databas


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Click Finish


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Three folders will be created.

Bidding

Bidding-ejb

Bidding-war

Bidding-ejb - Enterprise bean - right click - new - session bean

Give a name and package name

Choose stateful and Remote


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Give finish

This will create two java files in (Bidding-ejb - source packages session)

This is nothing but the bean class and the remote interface that maam explained

in class.

There will be three tabs on the left pane (Project, Files and Services)

Click on the services tab.

Open Databases.

If you have installed MySQL, the first option in that will be MySQL server at

localhost:3306[root].

Right clock on that and give connect.

Again right click on it and give Create database.

Give a name for the database.

This name will now appear in the list in the Services tab.


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Click on the + mark in it. Right click on Tables and choose Create Table.

Give a table name and whatever fields you want. Make only one field Primary

key by choosing Key


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Click OK.

Right click on the table and choose view data.

No data is available. To add data, choose the small button(with a + symbol)

displayed above the column names. Add the data and click OK.

Go back to Project tab.

Bidding-ejb Enterprise Bean right click new Entity Class from database.

Choose New Data Source


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Give a JNDI name

And choose the database that you created.

The tables available in the mentioned database will be displayed. Add the table

to the Selected Tables list.


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Give Next. In the screen that follows, Click on Create Persistance Unit. This is

important.(you should remember this name. This is again used in the program).

Give a name and click on create in the Table Generation Strategy. Then click

Create.


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Choose Next -> Finish. Now, you have finished creating the entity bean and the

session bean. Now, you have to make a connection between your session and

entity bean.

Goto your session bean class. (Bidding-ejb source packages session)

This shows three java files now. The one with the same name as your database

table is your entity bean class. It contains a get and set method for each field in

the table.

Open the session bean class. Right click - Persistence Use Persistence

manager


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This will add the required code automatically.

Inside the class, there will be a line that goes like this

private EntityManager em;

Below this line, type the following line.

private EntityManagerFactory emf;

A small bulb symbol will appear at the beginning of the line when you finish

typing this. Just click on it and choose Add import for

javax..persistence.EntityManagerFactory.

There will be another bulb symbol below. Click on whatever option it shows.


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Go to the bean class again. Right click and choose insert Code and choose

constructor. Just click on generate without selecting anything.

Type in the following lines inside the constructor.

emf = Persistence.createEntityManagerFactory("prod");

em = emf.createEntityManager();


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The prod inside the double quotes is the name of the persistent unit that you

gave previously.

As of now, I have created a database table that has two columns (name and

ID(primary key)). I have created a entity bean which the mapping of this

database table and I have created a Session Bean.

Now all that remains on the server side is to connect this session bean with the

entity bean.

In this program, the user will enter an ID and the corresponding name will be

returned.

Now, right click on the bean class and choose insert code and Add Business

Method.


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This method gives in and ID and gets the Name

Inside the getName() method,Type in

Name n = em. find(Name.class, id);

i.e you are creating an object for the entity bean class(Name) and find file called

Name.class passing the primary key id.


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Instead of returning null, type in

return n.getName();


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The server side is over. Now, we just have to create the client side JSP file.

Goto Bidding-war webpages index.jsp

In index.jsp, provide the a text box and a button in a form whose action is calling

a servlet named getServlet

Code:-


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JSP Page

Hello World!

To create the servlet, Right click on WEB-INF new servlet

Give the servlet name as getServlet, give a package name , give next and then

finish.

Right click in the getServlet class insert code Call Enterprise Bean

Choose the session bean class and click OK.


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This will create an object for the Remote Interface inside the servlet.

We first have to obtain the ID from the JSP and send it to the Session bean class

which will in turn send it to the entity bean class and retrieve the corresponding

Name.

Inside the try block, type in the following.


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int id = Integer.parseInt(request.getParameter("id"));

String name = statefulBean.getName(id);

out.println("the ID is " + id + "\n");

out.println("The correspoding name is " + name);

TO INSERT A ROW INTO THE DATABASE:-

I have considered a simple signup module where the user will enter a new

username and password and send it to a servlet which will inturn send it to a

method present in the session bean class.

Here, I have created a method named setPassword to obtain the username and

password from the servlet , create an Entity class object and insert the data into

the database.

public void setPassword(String username, String password)

{

Login l = new Login();

l.setUsername(username);

l.setPassword(password);

em.persist(l);

}


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The method persist() is used to insert the elements.

P.S: I havent validated the data input by the user. If you want, it can be done

using client side javascript, or the servlet that can check if that username already

exists in the database.

Now, Clean and Build all the three components and run Bidding.

If everything goes right, for the input

The output should be


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