比XML更好用的Java Annotation

JavaTWO 專業技術大會 Java Annotation 李日貴 (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

@Annotation Course1 Introduction

What’s annotation Begin with “@” An Interface Set Values @Annotation @Annotation(“someValue”) @Annotation(var1=“someA”,var2=“someB”) @Annotation(value={“Apple”, “Banana”, “Cherry”})

@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 } }

@Annotation Course 2 Servlet 3.0

Servlet 2.5 package 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 3.0 package 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); } } @WebListener public class SlowQueueListener implements ServletContextListener { public void contextInitialized(ServletContextEvent sce) { … } }

EJB 2.x public interface CalculatorLocal extends EJBLocalObject {..} public interface CalculatorLocalHome extends EJBLocalHome {..} public class CalculatorBean implements SessionBean { .. } 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 @Local public interface CalculatorLocal extends EJBLocalObject {..} public interface CalculatorHome extends EJBHome {..} @Stateless public class CalculatorBean implements CalculatorLocal{ .. } ejb-jar.xml

EJB 3.1 (LocalBean) @Local public interface CalculatorLocal extends EJBLocalObject {..} public interface CalculatorHome extends EJBHome {..} @Stateless public class CalculatorBean implements CalculatorLocal { .. } ejb-jar.xml

Singleton SessionBean @Singleton @ConcurrencyManagement(ConcurrencyManagementType.CONTAINER) public class SingletonBean { private int clickCount = 0; @Lock(LockType.WRITE) public int getClickCount() { return clickCount++; } } //Thread-Safe, Transactional

Schedule Timer @Singleton public class TransFileBean { @Schedule(minute=“0”,hour=“4”,dayOfMonth=“Last”) public void trans() { // do transfer } }

@Annotation Course 4 WebServices

WebServices “ Big” WebServices SOAP JAX-WS javax.jws.* RESTful WebServices REST JAX-RS javax.ws.rs.*

SOAP WebService import javax.jws. WebMethod; import javax.jws. WebService; @WebService(serviceName=“helloService”) public class Hello { @WebMethod public String sayHello(String name) { return “Hello “+name; } }

RESTful WebService import 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"; } }

Resource Injection JEE5 @WebServlet(“/product”) public ProductServlet extends HttpServlet { @Inject private ProductBean productBean; .. } @Stateless public class ProductBean { .. }

Ambiguous Inject @Qualifier public @interface CarPolicyNo { } @Qualifier public @interface FirePolicyNo { } @CarPolicyNoGenerator public class CarPolicyNoGenerator implements PolicyNoGenerator {.. } @FirePolicyNoGenerator public class FirePolicyNoGenerator implements PolicyNoGenerator{ .. } public class FireService { @Inject @FirePolicyNoGenerator private PolicyNoGenerator policyNoGenerator; }

@Produces public class DatabaseProducer { @Produces @PersistenceContext(unitName=“ds1”) @FireDatabase private EntityManager em; } public class FireService { @Inject @FireDatabase private EntityManager em; }

@Annotation Course 6 Opensources

jUnit 3.x import junit.framework.Assert; import junit.framework.TestCase; public class CalculateServiceTest3 extends TestCase { public void setUp () throws Exception { } public void test Sum() { int actual = new CalculateService().sum(3,5); Assert.assertEquals( 8 , actual ); } public void tearDown () throws Exception { } }

jUnit 4.x public class CalculateServiceTest4 extends TestCase { @BeforeClass public static void setUpBeforeClass() throws Exception { } @Before public void beforeTest() throws Exception { } @Test public void theSum() { Assert.assertEquals(8, new CalculateService().sum(3, 5)) ; } @After public void afterTest() throws Exception { } @AfterClass public 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> @Service public class NewsService { @Autowired private NewsDao newsDao; }

Spring 3.0 @Named public class NewsService { @Inject private NewsDao newsDao; }

Spring 3.0 @Configuration public class AppConfig { private @Value(“#{sysprop.dbURL}”) String dbURL; private @Value(“#{sysprop.username}”) String username; private @Value(“#{sysprop.password}”) String password; @Bean public 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 … } }

@Annotation Course 7 Javassist / ASM

Reflection Class 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 values ClassPool 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 ASM public class ScanMyDocVisitor implements ClassVisitor { public AnnotationVisistor visitAnnotation(String desc, boolean visible) { } } // in Controller for(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(); .. }

比XML更好用的Java Annotation

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