有状态会话bean是一种企业bean,它保留与客户端的会话状态.有状态会话bean根据其名称在其实例变量中保持关联的客户端状态. EJB容器创建一个单独的有状态会话bean来处理客户端的每个请求.一旦请求范围结束,就会销毁statelful会话bean.
以下是创建有状态所需的步骤EJB :
创建公开业务方法的远程/本地接口.
EJB客户端应用程序将使用此接口.
如果EJB客户端位于EJB所在的相同环境中,请使用@Local批注需要部署会话bean.
如果EJB客户端位于需要部署EJB会话bean的不同环境中,请使用@Remote注释.
创建一个有状态会话bean,实现上述接口.
使用@Stateful注释表示它有状态的豆. EJB容器在部署期间自动创建读取此批注所需的相关配置或接口.
import javax.ejb.Remote; @Remote public interface LibraryStatefulSessionBeanRemote { //add business method declarations }
@Stateful public class LibraryStatefulSessionBean implements LibraryStatefulSessionBeanRemote { //implement business method }
让我们创建一个测试EJB应用程序来测试有状态EJB.
Step | 描述 |
---|---|
1 | 使用名称创建项目在 EJB : 中解释的 com.it1352.stateful 下的 EjbComponent ;创建应用程序章节.您还可以使用在本章中 EJB - 创建应用程序章节中创建的项目来了解有状态EJB概念. |
2 | 创建 LibraryStatefulSessionBean.java 和 LibraryStatefulSessionBeanRemote 如 EJB&minus中所述;创建应用程序章节.保持其余文件不变. |
3 | 清理并构建应用程序以确保业务逻辑按照要求运行. |
4 | 最后,在JBoss Application Server上以jar文件的形式部署应用程序.如果JBoss应用服务器尚未启动,它将自动启动. |
5 | 现在创建EJB客户端,一个基于控制台的应用程序,其方式与主题创建 EJB - 创建应用程序章节中所述的相同客户端访问EJB . |
package com.IT屋.stateful; import java.util.List; import javax.ejb.Remote; @Remote public interface LibraryStatefulSessionBeanRemote { void addBook(String bookName); List getBooks(); }
package com. it1352.stateful; import java.util.ArrayList; import java.util.List; import javax.ejb.Stateful; @Stateful public class LibraryStatefulSessionBean implements LibraryStatefulSessionBeanRemote { List<String> bookShelf; public LibraryStatefulSessionBean() { bookShelf = new ArrayList<String>(); } public void addBook(String bookName) { bookShelf.add(bookName); } public List<String> getBooks() { return bookShelf; } }
一旦部署EjbComponent关于JBOSS的项目,请注意jboss日志.
JBoss已自动为会话bean创建了一个JNDI条目 : LibraryStatefulSessionBean/remote .
我们将使用此查找字符串来获取类型为 : com的远程业务对象. it1352.stateful.LibraryStatefulSessionBeanRemote
... 16:30:01,401 INFO [JndiSessionRegistrarBase] Binding the following Entries in Global JNDI: LibraryStatefulSessionBean/remote - EJB3.x Default Remote Business Interface LibraryStatefulSessionBean/remote-com.IT屋.stateful.LibraryStatefulSessionBeanRemote - EJB3.x Remote Business Interface 16:30:02,723 INFO [SessionSpecContainer] Starting jboss.j2ee:jar=EjbComponent.jar,name=LibraryStatefulSessionBean,service=EJB3 16:30:02,723 INFO [EJBContainer] STARTED EJB: com.IT屋.stateful.LibraryStatefulSessionBeanRemote ejbName: LibraryStatefulSessionBean 16:30:02,731 INFO [JndiSessionRegistrarBase] Binding the following Entries in Global JNDI: LibraryStatefulSessionBean/remote - EJB3.x Default Remote Business Interface LibraryStatefulSessionBean/remote-com.IT屋.stateful.LibraryStatefulSessionBeanRemote - EJB3.x Remote Business Interface ...
java.naming.factory.initial = org.jnp.interfaces.NamingContextFactory java.naming.factory.url.pkgs = org.jboss.naming:org.jnp.interfaces java.naming.provider.url = localhost
这些属性用于初始化java命名服务的InitialContext对象.
InitialContext对象将用于查找有状态会话bean.
package com.it1352.test; import com.it1352.stateful.LibraryStatefulSessionBeanRemote; import java.io.BufferedReader; import java.io.FileInputStream; import java.io.IOException; import java.io.InputStreamReader; import java.util.List; import java.util.Properties; import javax.naming.InitialContext; import javax.naming.NamingException; public class EJBTester { BufferedReader brConsoleReader = null; Properties props; InitialContext ctx; { props = new Properties(); try { props.load(new FileInputStream("jndi.properties")); } catch (IOException ex) { ex.printStackTrace(); } try { ctx = new InitialContext(props); } catch (NamingException ex) { ex.printStackTrace(); } brConsoleReader = new BufferedReader(new InputStreamReader(System.in)); } public static void main(String[] args) { EJBTester ejbTester = new EJBTester(); ejbTester.testStatelessEjb(); } private void showGUI() { System.out.println("**********************"); System.out.println("Welcome to Book Store"); System.out.println("**********************"); System.out.print("Options \n1. Add Book\n2. Exit \nEnter Choice: "); } private void testStatelessEjb() { try { int choice = 1; LibraryStatefulSessionBeanRemote libraryBean = LibraryStatefulSessionBeanRemote)ctx.lookup("LibraryStatefulSessionBean/remote"); while (choice != 2) { String bookName; showGUI(); String strChoice = brConsoleReader.readLine(); choice = Integer.parseInt(strChoice); if (choice == 1) { System.out.print("Enter book name: "); bookName = brConsoleReader.readLine(); Book book = new Book(); book.setName(bookName); libraryBean.addBook(book); } else if (choice == 2) { break; } } List<Book> booksList = libraryBean.getBooks(); System.out.println("Book(s) entered so far: " + booksList.size()); int i = 0; for (Book book:booksList) { System.out.println((i+1)+". " + book.getName()); i++; } LibraryStatefulSessionBeanRemote libraryBean1 = (LibraryStatefulSessionBeanRemote)ctx.lookup("LibraryStatefulSessionBean/remote"); List<String> booksList1 = libraryBean1.getBooks(); System.out.println( "***Using second lookup to get library stateful object***"); System.out.println( "Book(s) entered so far: " + booksList1.size()); for (int i = 0; i < booksList1.size(); ++i) { System.out.println((i+1)+". " + booksList1.get(i)); } } catch (Exception e) { System.out.println(e.getMessage()); e.printStackTrace(); }finally { try { if(brConsoleReader !=null) { brConsoleReader.close(); } } catch (IOException ex) { System.out.println(ex.getMessage()); } } } }
EJBTester执行以下任务 :
从jndi.properties加载属性并初始化InitialContext对象.
在testStatefulEjb()方法中,使用name - "LibraryStatefulSessionBean/remote"完成jndi查找以获取远程业务对象(有状态ejb).
然后向用户显示库存储用户界面,并要求他/她输入选项.
如果用户输入1,系统会要求输入书名并保存本书使用有状态会话bean addBook()方法.会话Bean将书存储在其实例变量中.
如果用户输入2,系统将使用有状态会话bean getBooks()方法检索书籍并退出.
然后使用名称"LibraryStatefulSessionBean/remote"完成另一个jndi查找,以再次获取远程业务对象(有状态EJB)并完成书籍列表./p>
在项目资源管理器中找到EJBTester.java.右键单击EJBTester类并选择运行文件.
验证Netbeans控制台中的以下输出 :
run: ********************** Welcome to Book Store ********************** Options 1. Add Book 2. Exit Enter Choice: 1 Enter book name: Learn Java ********************** Welcome to Book Store ********************** Options 1. Add Book 2. Exit Enter Choice: 2 Book(s) entered so far: 1 1. Learn Java ***Using second lookup to get library stateful object*** Book(s) entered so far: 0 BUILD SUCCESSFUL (total time: 13 seconds)
找到EJBTester.java在项目资源管理器中.右键单击EJBTester类并选择运行文件.
在Netbeans控制台中验证以下输出.
run: ********************** Welcome to Book Store ********************** Options 1. Add Book 2. Exit Enter Choice: 2 Book(s) entered so far: 0 ***Using second lookup to get library stateful object*** Book(s) entered so far: 0 BUILD SUCCESSFUL (total time: 12 seconds)
上面显示的输出表明每次查找都有一个不同的有状态EJB返回实例
有状态EJB对象仅保留单个会话的值.和第二轮一样,我们
没有得到任何书籍价值.