比xml更好用的java annotation

JavaTWO JavaTWO 專業技術大會專業技術大會Java AnnotationJava Annotation李日貴李日貴 (jini)(jini)

About Me

• jini@JWorld.TW ( jakarta99 )• SoftLeader Tech. Corp. President since 2002• Focus on dev in Java enterprise applications for

Insurances, Banking and Betting.• Researching and Sharing Java Opensources• My Google+ (http://gplus.to/jakarta99)• Single now

Agenda

• Introduction• Servlet 3.0• EJB 3.1• WebServices• CDI• Opensources• Javassist / ASM

@AnnotationCourse1

Introduction

What’s annotation

• Begin with “@” • An Interface• Set Values

– @Annotation– @Annotation(“someValue”)– @Annotation(var1=“someA”,var2=“someB”)– @Annotation(value={“Apple”, “Banana”,

“Cherry”})

RetentionPolicy

@Annotation Runtime

• Default value• Stereotype

– Find the classes contain @Annotation

– Initialize them as what you want

– To generate the codes or xml and etc..

@Target(ElementType)@AnnoTarget(TYPE)public class TheTarget {

@AnnoTarget(FIELD)private String globalMsg;@AnnoTarget(CONSTRUCTOR)public TheTarget() {

// This is a constructor}@AnnoTarget(METHOD)public void someMethod(@AnnoTarget (PARAMETER) String myParam) {

// This is a method}

}

@AnnotationCourse 2 Servlet 3.0

Servlet 2.5package javatwo.annotation;public class CatServlet extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

// do something}

}

web.xml<web-app>

<servlet><servlet-name>CatServlet</servlet-name><servlet-class>javatwo.annotation.CatServlet</servlet-class>

</servlet><servlet-mapping>

<servlet-name>CatServlet</servlet-name><url-pattern>/cat</url-pattern>

</servlet-mapping></web-app>

Servlet 3.0package javatwo.annotation;@WebServlet(“/cat”)public class CatServlet extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

// do something}

}

@WebServlet(name = "catServlet", urlPatterns = "/cat", initParams = { @WebInitParam(name = "name", value = "bobo") })

Servlet 3.0

• No web.xml needed– @WebServlet - Define a Servlet– @WebFilter - Define a Filter– @WebListener - Define a Listener– @WebInitParam- Define init parameter– @MultipartConfig- Define upload properties

• Can use web.xml to override values that specified by the Annotations.

FileUpload in Servlet 3.0@WebServlet(“/upload”)@MultipartConfig(location=“c:\\tmp”)public class FileUploadServlet extends HttpServlet {

public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {Collection<Part> parts = request.getParts();for( Part part:parts) {

part.write(“upload.txt”); // save to c:\tmp\upload.txt}

}

set Async in Servlet 3.0@WebServlet(name=“AsyncServlet”, urlPatterns=“/async”,

asyncSupported=“true”)public class AsyncServlet extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response) {

AsyncContext aCtx = request.startAsync(request, response); ServletContext sc = request.getServletContext();((Queue<AsyncContext>)sc.getAttribute(“slowQueue")).add(aCtx);

}}@WebListenerpublic class SlowQueueListener implements ServletContextListener {

public void contextInitialized(ServletContextEvent sce) { … }}

@AnnotationCourse 3 EJB 3.1

EJB 2.x1. public interface CalculatorLocal extends EJBLocalObject {..}2. public interface CalculatorLocalHome extends EJBLocalHome {..}3. public class CalculatorBean implements SessionBean { .. }4. ejb-jar.xml<ejb-jar>

<enterprise-beans><session>

<ejb-name>calculator</ejb-name><local-home>CalculatorLocalHome</local-home><local>CalculatorLocal</local><ejb-class>CalculatorBean</ejb-class><session-type>Stateless</session-type><transaction-type>Container</transaction-type>

</session></enterprise-beans>

</ejb-jar>

EJB 3.0

1. @Local public interface CalculatorLocal extends EJBLocalObject {..}

2. public interface CalculatorHome extends EJBHome {..}

3. @Stateless public class CalculatorBean implements CalculatorLocal{ .. }

4. ejb-jar.xml

EJB 3.1 (LocalBean)

1. @Local public interface CalculatorLocal extends EJBLocalObject {..}

2. public interface CalculatorHome extends EJBHome {..}

3. @Stateless public class CalculatorBean implements CalculatorLocal{ .. }

4. ejb-jar.xml

Singleton SessionBean@Singleton@ConcurrencyManagement(ConcurrencyManagementT

ype.CONTAINER)public class SingletonBean {

private int clickCount = 0;@Lock(LockType.WRITE)public int getClickCount() {

return clickCount++;}

}

//Thread-Safe, Transactional

Schedule Timer@Singletonpublic class TransFileBean {

@Schedule(minute=“0”,hour=“4”,dayOfMonth=“Last”)public void trans() {

// do transfer}

}

@AnnotationCourse 4

WebServices

WebServices

• “Big” WebServices– SOAP– JAX-WS– javax.jws.*

• RESTful WebServices– REST– JAX-RS– javax.ws.rs.*

SOAP WebServiceimport javax.jws.WebMethod;import javax.jws.WebService;

@WebService(serviceName=“helloService”)public class Hello {

@WebMethodpublic String sayHello(String name) {

return “Hello “+name;}

}

RESTful WebServiceimport javax.ws.rs.GET;import javax.ws.rs.Path;import javax.ws.rs.PathParam;import javax.ws.rs.Produces;import javax.ws.rs.core.MediaType;

@Path("/helloREST/{name}")public class HelloREST {

@GET@Produces(MediaType.TEXT_PLAIN)public String getHello(@PathParam("name") String name) {

return "Hello *"+name+"* from JAX-RS";}

}

@AnnotationCourse 5

CDI

Resource Injection JEE5@WebServlet(“/product”)public ProductServlet extends HttpServlet {

@Injectprivate ProductBean productBean;..

}

@Statelesspublic class ProductBean {

..}

Ambiguous Inject@Qualifierpublic @interface CarPolicyNo { }

@Qualifierpublic @interface FirePolicyNo { }

@CarPolicyNoGeneratorpublic class CarPolicyNoGenerator implements PolicyNoGenerator {.. }

@FirePolicyNoGeneratorpublic class FirePolicyNoGenerator implements PolicyNoGenerator{ .. }

public class FireService {@Inject@FirePolicyNoGeneratorprivate PolicyNoGenerator policyNoGenerator;

}

@Producespublic class DatabaseProducer {

@Produces @PersistenceContext(unitName=“ds1”)@FireDatabaseprivate EntityManager em;

}

public class FireService {@Inject @FireDatabaseprivate EntityManager em;

}

@AnnotationCourse 6

Opensources

jUnit 3.ximport junit.framework.Assert;import junit.framework.TestCase;

public class CalculateServiceTest3 extends TestCase {public void setUp() throws Exception { }public void testSum() {

int actual = new CalculateService().sum(3,5);Assert.assertEquals( 8 , actual );

}public void tearDown() throws Exception { }

}

jUnit 4.xpublic class CalculateServiceTest4 extends TestCase {

@BeforeClasspublic static void setUpBeforeClass() throws Exception { }@Beforepublic void beforeTest() throws Exception { }@Testpublic void theSum() {

Assert.assertEquals(8, new CalculateService().sum(3, 5)) ; } @Afterpublic void afterTest() throws Exception { }@AfterClasspublic static void tearDownAfterClass() throws Exception { }

}

Spring 2.5<beans>

<bean id=“newsDao” class=“javatwo.annotation.spring.NewsDao”/><bean id=“newsService” class=“javatwo.annotation.spring.NewsService”>

<property name=“newsDao”><ref bean=“newsDao”/>

</property></bean>

</beans>

@Servicepublic class NewsService {

@Autowiredprivate NewsDao newsDao;

}

Spring 3.0

@Namedpublic class NewsService {

@Injectprivate NewsDao newsDao;

}

Spring 3.0@Configurationpublic class AppConfig {

private @Value(“#{sysprop.dbURL}”) String dbURL;private @Value(“#{sysprop.username}”) String username;private @Value(“#{sysprop.password}”) String password;@Beanpublic DataSource dataSource() {

return new DriverManagerDataSource(dbURL, username, password );}

}

MVC in Spring3.0@Controller@RequestMapping(“/news”)public class NewsController {

@RequestMaaping(value=“{id}”, method=RequestMethod.GET) public ModelAndView getById(@PathVariable(“id”) Long id) {

return …}

}

@AnnotationCourse 7

Javassist / ASM

ReflectionClass myClass = MyClass.class;Method[] myMethods = myClass.getMethods();for(Method myMethod:myMethods) {

Annotation[] annotations = myMethod.getAnnotations();for( Annotation annotation:annotations) {

if( annotation instanceof MyAnno ) {MyAnno myAnno = (MyAnno) annotation;// do something

}}

}

Scan in ClassLoader• scannotation.sf.net project ( based on javassist )

URL[] urls = ClasspathUrlFinder.findClassPaths();AnnotationDB db = new AnnotationDB();db.scanArchives(urls);Map<String, Set<String>> annoIndex = db.getAnnotationIndex();Set<String> aClassNames =

annoIndex.get(“javatwo.annotation.MyAnno”);for( String aClassName:aClassNames ) {

..}// in Web,

WarUrlFinder.findWebInfClassesPath(this.getServletContext());

Get the Annotation valuesClassPool pool = ClassPool.getDefault();pool.insertClassPath(new ClassClassPath(this.getClass));CtClass cc = pool.get(aClassName);Object[] annos = cc.getAnnotations();for( Object anno : annos ) {

if( anno instanceof MyAnno ) {MyAnno myAnno = (MyAnno) anno;// do myAnno.var1(), myAnno.var2()

}}

Class R/W in ASMpublic class ScanMyDocVisitor implements ClassVisitor {

public AnnotationVisistor visitAnnotation(String desc, boolean visible) {}

}// in Controllerfor(String className: classNames){

ScanMyDocVisitor sv = new ScanMyDocVisitor();ClassReader cr = new ClassReader(Thread.currentThread().getContextClassLoader().getResouceAsStream(className));cr.accept(sv, 0);List<AnnotationNode> annotationList = sv.getVisibleAnnotations();..

}