EJB 3.0提供了将JAVA POJO(Plain Old Java Object)嵌入到实体bean中的选项,并允许使用嵌入式POJO类的方法映射列名.要嵌入的java POJO必须注释为@Embeddable.
@Embeddable public class Publisher implements Serializable{ private String name; private String address; ... }
上述类可以使用@Embedded注释嵌入.
@Entity public class Book implements Serializable{ private int id; private String name; private Publisher publisher; ... @Embedded @AttributeOverrides({ @AttributeOverride(name = "name", column = @Column(name = "PUBLISHER")), @AttributeOverride(name = "address", column = @Column(name = "PUBLISHER_ADDRESS")) }) public Publisher getPublisher() { return publisher; } ... }
让我们创建一个测试EJB应用程序来测试EJB 3.0中的嵌入对象.
Step | 描述 |
---|---|
1 | 在 com.it1352.entity 包下创建一个名为 EjbComponent 的项目,如 EJB - 创建应用程序章节.请使用本章中 EJB - Persistence 章节中创建的项目来理解EJB概念中的嵌入对象. |
2 | 在包 com.it1352下创建 Publisher.java .entity ,如 EJB - 创建应用程序章节中所述.保持其余文件不变. |
3 | 在包 com.it1352.entity 下创建 Book.java .使用 EJB - Persistence 章节作为参考.保持其余文件不变. |
4 | 清理并构建应用程序以确保业务逻辑按照要求运行. |
5 | 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. |
6 | 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 . |
CREATE TABLE book ( id integer PRIMARY KEY, name varchar(50) ); Alter table book add publisher varchar(100); Alter table book add publisher_address varchar(200);
package com.it1352.entity; import java.io.Serializable; import javax.persistence.Embeddable; @Embeddable public class Publisher implements Serializable{ private String name; private String address; public Publisher() {} public Publisher(String name, String address) { this.name = name; this.address = address; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getAddress() { return address; } public void setAddress(String address) { this.address = address; } public String toString() { return name + "," + address; } }
package com.it1352.entity; import com.it1352.callback.BookCallbackListener; import java.io.Serializable; import javax.persistence.AttributeOverride; import javax.persistence.AttributeOverrides; import javax.persistence.Column; import javax.persistence.Embedded; import javax.persistence.Entity; import javax.persistence.EntityListeners; import javax.persistence.GeneratedValue; import javax.persistence.GenerationType; import javax.persistence.Id; import javax.persistence.Table; @Entity @Table(name="book") public class Book implements Serializable{ private int id; private String name; private Publisher publisher; public Book() { } @Id @GeneratedValue(strategy= GenerationType.IDENTITY) @Column(name="id") public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } @Embedded @AttributeOverrides({ @AttributeOverride(name = "name", column = @Column(name = "PUBLISHER")), @AttributeOverride(name = "address", column = @Column(name = "PUBLISHER_ADDRESS")) }) public Publisher getPublisher() { return publisher; } public void setPublisher(Publisher publisher) { this.publisher = publisher; } }
package com.it1352.stateless; import com.it1352.entity.Book; import java.util.List; import javax.ejb.Remote; @Remote public interface LibraryPersistentBeanRemote { void addBook(Book bookName); List<Book> getBooks(); }
import java.util.List; import javax.ejb.Stateless; import javax.persistence.EntityManager; import javax.persistence.PersistenceContext; @Stateless public class LibraryPersistentBean implements LibraryPersistentBeanRemote { public LibraryPersistentBean() { } @PersistenceContext(unitName="EjbComponentPU") private EntityManager entityManager; public void addBook(Book book) { entityManager.persist(book); } public List<Book> getBooks() { return entityManager.createQuery("From Book").getResultList(); } }
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 : LibraryPersistentBean/remote .
我们将使用此查找字符串来获取类型为&minus的远程业务对象; com.it1352.interceptor.LibraryPersistentBeanRemote
... 16:30:01,401 INFO [JndiSessionRegistrarBase] Binding the following Entries in Global JNDI: LibraryPersistentBean/remote - EJB3.x Default Remote Business Interface LibraryPersistentBean/remote-com.IT屋.interceptor.LibraryPersistentBeanRemote - EJB3.x Remote Business Interface 16:30:02,723 INFO [SessionSpecContainer] Starting jboss.j2ee:jar=EjbComponent.jar,name=LibraryPersistentBean,service=EJB3 16:30:02,723 INFO [EJBContainer] STARTED EJB: com.IT屋.interceptor.LibraryPersistentBeanRemote ejbName: LibraryPersistentBean 16:30:02,731 INFO [JndiSessionRegistrarBase] Binding the following Entries in Global JNDI: LibraryPersistentBean/remote - EJB3.x Default Remote Business Interface LibraryPersistentBean/remote-com.IT屋.interceptor.LibraryPersistentBeanRemote - 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对象将用于查找无状态会话bean.
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.testEmbeddedObjects(); } 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 testEmbeddedObjects() { try { int choice = 1; LibraryPersistentBeanRemote libraryBean = (LibraryPersistentBeanRemote) ctx.lookup("LibraryPersistentBean/remote"); while (choice != 2) { String bookName; String publisherName; String publisherAddress; showGUI(); String strChoice = brConsoleReader.readLine(); choice = Integer.parseInt(strChoice); if (choice == 1) { System.out.print("Enter book name: "); bookName = brConsoleReader.readLine(); System.out.print("Enter publisher name: "); publisherName = brConsoleReader.readLine(); System.out.print("Enter publisher address: "); publisherAddress = brConsoleReader.readLine(); Book book = new Book(); book.setName(bookName); book.setPublisher (new Publisher(publisherName,publisherAddress)); 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()); System.out.println("Publication: "+book.getPublisher()); 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testInterceptedEjb()方法中,使用名称"LibraryPersistenceBean/remote"完成jndi查找以获取远程业务对象(无状态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,则系统请求书名并使用无状态会话bean addBook()方法保存书籍.会话Bean将书籍存储在数据库中.
如果用户输入2,系统将使用无状态会话bean getBooks()方法检索书籍并退出.
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.
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: 1 Enter book name: learn html5 Enter publisher name: SAMS Enter publisher address: DELHI ********************** Welcome to Book Store ********************** Options 1. Add Book 2. Exit Enter Choice: 2 Book(s) entered so far: 1 1. learn html5 Publication: SAMS,DELHI BUILD SUCCESSFUL (total time: 21 seconds)