EJB嵌入對象

2018-12-08 19:19 更新

EJB 3.0提供選項，以嵌入Java POJO（普通Java對象）到一個實體bean，并允許與嵌入式POJO類的方法列名映射。一個java POJO被嵌入必須標注為@Embeddable。 

@Embeddable
public class Publisher implements Serializable{
   private String name;
   private String address;
   ...
}


上面的類可以使用@Embedded嵌入的注釋

@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;
   }
   ...
}


示例應用程序

讓我們創(chuàng)建一個測試EJB應用程序在EJB 3.0測試嵌入的對象。

步驟描述
1用包com.tutorialspoint.entity下一個名字EjbComponent在EJB作為解釋的創(chuàng)建項目-創(chuàng)建應用程序一章。請使用EJB創(chuàng)建的項目-持久章這樣本章了解EJB概念嵌入的對象。
2包下com.tutorialspoint.entity創(chuàng)建Publisher.java作為EJB解釋-創(chuàng)建應用程序一章。保持不變的文件其余部分。
3包下com.tutorialspoint.entity創(chuàng)建Book.java。使用EJB -持久章作為參考。保持不變的文件其余部分。
4清理并生成應用程序，確保業(yè)務邏輯正在按要求。
5最后，部署JBoss應用服務器上的jar文件的形式應用。如果尚未啟動JBoss應用服務器將自動被啟動。
6現在創(chuàng)建EJB客戶端，以同樣的方式一個基于控制臺的應用程序在EJB解釋-創(chuàng)建應用程序一章的主題創(chuàng)建客戶機訪問EJB。


創(chuàng)建/更改表書

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);


EJBComponent（EJB模塊）

Publisher.java 

package com.tutorialspoint.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;
   }    
}


Book.java 

package com.tutorialspoint.entity;

import com.tutorialspoint.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;
   }    
}


LibraryPersistentBeanRemote.java 

package com.tutorialspoint.stateless;

import com.tutorialspoint.entity.Book;
import java.util.List;
import javax.ejb.Remote;

@Remote
public interface LibraryPersistentBeanRemote {

   void addBook(Book bookName);

   List<Book> getBooks();
    
}


LibraryPersistentBean.java 

package com.tutorialspoint.stateless;

import com.tutorialspoint.entity.Book;
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();
   }
}

  • 一旦你部署JBoss上EjbComponent項目，注意jboss的日志。

  • JBoss已經具備自動創(chuàng)建我們的會話bean JNDI入口- LibraryPersistentBean /remote。

  • 我們將使用此查找字符串來獲得類型的遠程業(yè)務對象- com.tutorialspoint.interceptor.LibraryPersistentBeanRemote


JBoss應用服務器日志輸出

...
16:30:01,401 INFO  [JndiSessionRegistrarBase] Binding the following Entries in Global JNDI:
   LibraryPersistentBean/remote - EJB3.x Default Remote Business Interface
   LibraryPersistentBean/remote-com.tutorialspoint.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.tutorialspoint.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.tutorialspoint.interceptor.LibraryPersistentBeanRemote - EJB3.x Remote Business Interface
...


EJBTester（EJB客戶端）

jndi.properties 

java.naming.factory.initial=org.jnp.interfaces.NamingContextFactory
java.naming.factory.url.pkgs=org.jboss.naming:org.jnp.interfaces
java.naming.provider.url=localhost

  • 這些屬性用于初始化Java命名服務的InitialContext對象

  • InitialContext對象將被用于查找無狀態(tài)會話bean


EJBTester.java 

package com.tutorialspoint.test;
   
import com.tutorialspoint.stateful.LibraryBeanRemote;
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 
1. Add Book
2. Exit 
Enter 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做以下任務。

  • 從jndi.properties負荷特性和初始化InitialContext對象。

  • 在testInterceptedEjb（）方法，JNDI查找與名行 - “LibraryPersistenceBean /遠程”，以獲得遠程業(yè)務對象（無狀態(tài)EJB）。

  • 然后用戶顯示庫存儲用戶界面和他（她）被要求輸入選擇/。

  • 如果用戶輸入1，系統(tǒng)要求書名并保存使用無狀態(tài)會話bean addBook（）方法的書。會話bean存儲書數據庫。

  • 如果用戶輸入2，系統(tǒng)retrives使用無狀態(tài)會話bean getBooks（）方法，并退出書籍。


運行客戶端訪問EJB

在項目資源管理器中找到EJBTester.java。右鍵單擊EJBTester類并選擇運行文件 。

驗證Netbeans的控制臺下面的輸出。 

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)
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