JavaEE5学习笔记05-EJB之会话Bean(sessionBean)总结-----3

1.      有状态的会话Bean和helloworld

下面我们来看看有状态的SessionBean是否在可靠的调用中严格维护着它的实例变量。

下面看代码

ShopService接口

 

/**    *  * @author liuyan  *  */ @Remote public interface ShopService {     void addItem(String item);     Map<String, Integer> showItems();     void removeForClient(); }

实现类如下

 

@Stateful public class ShopServiceEAOImpl implements ShopService {       private Map<String, Integer> buyInfo = new HashMap<String, Integer>();       @Override     public void addItem(String item) {        if (buyInfo.containsKey(item)) {            buyInfo.put(item, buyInfo.get(item) + 1);        } else {            buyInfo.put(item, 1);        }     }       @Override     public Map<String, Integer> showItems() {        System.out.println("buyInfo:" + buyInfo);        return buyInfo;     }       @PostConstruct     public void postConstruct() {        System.out.println("有状态SessionBean：ShopServiceEAOImpl构造完毕");     }       @PreDestroy     public void preDestroy() {        System.out.println("调用毁灭对象之前的方法--preDestroy()");     }       @Remove     public void removeForClient() {        System.out.println("客户端调用了显示的移除EJBBean的方法！");     }   }

junit测试代码如下：

 

import java.util.Properties; import javax.naming.Context; import javax.naming.InitialContext; import javax.naming.NamingException; import junit.framework.TestCase; import ejb.sessionBean.ShopService;   public class TestStatefulSessionBean extends TestCase {       static ShopService shopService = null;       public Context init() {          …………………………         }         public void test01() throws NamingException {        if (shopService == null) {            Context context = init();            shopService = (ShopService) context                   .lookup("ShopServiceEAOImpl/remote");        }        shopService.addItem("素还真");        System.out.println(shopService.showItems());     }         public void test02() throws NamingException {        if (shopService == null) {            Context context = init();            shopService = (ShopService) context                   .lookup("ShopServiceEAOImpl/remote");        }        shopService.addItem("素还真");        System.out.println(shopService.showItems());       }         public void test03() throws NamingException {        if (shopService == null) {            Context context = init();            shopService = (ShopService) context                   .lookup("ShopServiceEAOImpl/remote");        }               shopService.addItem("叶小钗");        System.out.println(shopService.showItems());     }         public void test04() throws NamingException {        if (shopService == null) {            Context context = init();            shopService = (ShopService) context                   .lookup("ShopServiceEAOImpl/remote");        }        System.out.println(shopService.showItems());     } }

每次单独调用testXXX的时候服务端的结果总是单一的元素，可以看出，服务端的实例变量在每次、分别调用的时候都是穿件了一个新的、刚出锅的、热乎乎、无污染的实例变量。（在此代码中就不列出结果了）

加入我们一气呵成执行此用例呢？让测试用例的静态变量所有方法中处在一个JVM中。

结果如下

 

11:32:09,896 INFO  [STDOUT] 有状态SessionBean：ShopServiceEAOImpl构造完毕 11:32:10,022 INFO  [STDOUT] buyInfo:{素还真=1} 11:32:10,038 INFO  [STDOUT] buyInfo:{素还真=2} 11:32:10,069 INFO  [STDOUT] buyInfo:{素还真=2, 叶小钗=1} 11:32:10,080 INFO  [STDOUT] buyInfo:{素还真=2, 叶小钗=1}

由此观之在同一次调用中，服务端的无状态会话Bean确实是维护了实例变量的属性值及其状态。不会像无状态的会话调用，结果无法预期……