激活狀態bean package com.wiley.compBooks.roman.session.count; import javax.ejb.*; import java.rmi.RemoteException; /** * These are CountBean´s business logic methods. * * This interface is what clients Operate on when they * interact with EJB objects. The container vendor will implement this interface; the implemented object is * the EJB Object, which delegates invocations to the * actual bean. */ public interface Count extends EJBObject { /** * Increments the int stored as conversational state */ public int count() throws RemoteException; } Source Count.java
package com.wiley.compBooks.roman.session.count; import javax.ejb.*; /** * Demonstration Stateful Session Bean. This bean is * initialized to some integer value and has a business * method that increments the value. * * This example shows the basics of how to write a stateful * session bean and how passivation/activation works. */ public class CountBean implements SessionBean { private SessionContext ctx; // The current counter is our conversational state. public int val; // // Business methods // /** * Counts up */ public int count() { System.out.println("count()"); return ++val; } // // EJB-required methods // public void ejbCreate(int val) throws CreateException { this.val = val; System.out.println("ejbCreate()"); } public void ejbRemove() { System.out.println("ejbRemove()"); } public void ejbActivate() { System.out.println("ejbActivate()"); } public void ejbPassivate() { System.out.println("ejbPassivate()"); } public void setSessionContext(SessionContext ctx) { } } Source CountBean.java Bean實現了javax.ejb.SessionBean。所以，它必須定義所有SessionBean定義的方法。 OjbCreate()初始化帶了val的參數。它將作為counter的初始狀態。在鈍化和激活bean的過程中，val變量被保護。
計數bean的home接口 package com.wiley.compBooks.roman.session.count; import javax.ejb.*; import java.rmi.RemoteException; /** * This is the home interface for CountBean. This interface * is implemented by the EJB Server´s glue-code tools - the * implemented object is called the Home Object and serves * as a factory for EJB Objects. * * One create() method is in this Home Interface, which * corresponds to the ejbCreate() method in the CountBean file. */ public interface CountHome extends EJBHome { /* * This method creates the EJB Object. * * @param val Value to initialize counter to * * @return The newly created EJB Object. */ Count create(int val) throws RemoteException, CreateException; } Source CountHome.java. 計數bean的配置描述符
計數bean的配置描述符 計數bean的環境屬性 生成計數bean的Ejb-jar文件 計數bean的客戶端代碼 package com.wiley.compBooks.roman.session.count; import javax.ejb.*; import javax.naming.*; import java.util.Properties; /** * This class is a simple example of client code that invokes * methods on a simple Stateless Enterprise Bean. * * We create 3 EJB Objects in this example, but we allow * the container to have only 2 in memory. This illustrates how * beans are passivated to storage. */ public class CountClient { public static void main(String[] args) { try { /* * Get System properties for JNDI initialization */ Properties props = System.getProperties(); /* * Get a reference to the Home Object - the * factory for EJB Objects */ Source CountClient.java 1、需要JNDL初始化上下文 2、使用JNDL定位home接口 3、使用home對象建立3個不同的計數EJB對象，因此也就和三個不同的客戶端建立了會話 4、配置描述符限制了同時只能有兩個bean工作，因此3個bean中一定有鈍化的。在調用ejbPassivate()時，打印一條信息。 5、在每個EJB對象上調用count()方法，調用ejbActivate()方法激活bean，該方法打印一條信息。 6、最后所有的EJB對象被刪除。 package com.wiley.compBooks.roman.session.count; import javax.ejb.*; import javax.naming.*; import java.util.Properties; /** * This class is a simple example of client code that invokes * methods on a simple Stateless Enterprise Bean. * * We create 3 EJB Objects in this example, but we allow * the container to have only 2 in memory. This illustrates how * beans are passivated to storage. */ public class CountClient { public static void main(String[] args) { try { /* * Get System properties for JNDI initialization */ Properties props = System.getProperties(); /* * Get a reference to the Home Object - the * factory for EJB Objects */ Context ctx = new InitialContext(props); CountHome home = (CountHome) ctx.lookup("CountHome"); /* * An array to hold 3 Count EJB Objects */ Count count[] = new Count[3]; int countVal = 0; /* * Create and count() on each member of array */ System.out.println("Instantiating beans..."); for (int i=0; i < 3; i++) { /* * Create an EJB Object and initialize * it to the current count value. */ count[i] = home.create(countVal); /* * Add 1 and print */ countVal = count[i].count(); System.out.println(countVal); /* * Sleep for 1/2 second */ Thread.sleep(500); } /* * Let´s call count() on each EJB Object to * make sure the beans were passivated and * activated properly. */ System.out.println("Calling count() on beans..."); for (int i=0; i < 3; i++) { /* * Add 1 and print */ countVal = count[i].count(); System.out.println(countVal); /* * Sleep for 1/2 second */ Thread.sleep(500); } /* * Done with EJB Objects, so remove them */ for (int i=0; i < 3; i++) { count[i].remove(); } } catch (Exception e) { e.printStackTrace(); } } } Source CountClient.java 運行客戶端： 對于BEA的WebLogic，執行： java -Djava.naming.factory.initial= weblogic.jndi.TengahInitialContextFactory -Djava.naming.provider.url= t3://localhost:7001 com.wiley.compBooks.roman.session.count.CountClient 客戶端輸出： Instantiating beans... 1 2 3 Calling count() on beans... 2 3 4 服務端輸出： ejbCreate() count() ejbCreate() count() ejbCreate() ejbPassivate() count() ejbPassivate() ejbActivate() count() ejbPassivate() ejbActivate() count() ejbPassivate() ejbActivate() count() ejbPassivate() ejbActivate() ejbRemove() ejbActivate() ejbRemove() ejbRemove()
