EJB实现简单CRUD操作和生命周期探讨

向右看齐 2022-05-10 10:04 120阅读 0赞

### 环境 ###

MyEclipse 8.6 + JBoss 6.0 + JDK 1.6.13 + EJB 3.0

### 问题 ###

### 解决 ###

1.       配置JBoss数据源

a)         数据源参考配置文件

jboss-6.0.0.Final/docs/examples/jca/\*\*-ds.xml

b)         将配置文件放到站点根目录下

jboss-6.0.0.Final/server/default/deploy

c)         将connector加入站点

server/default/lib

d)         配置相关的参数

<jndi-name>MySqlDS</jndi-name>

<connection-url>jdbc:mysql://xxx:3306/xxx</connection-url>

<driver-class>com.mysql.jdbc.Driver</driver-class>

<user-name>xxx</user-name>

e)         启动JBoss

2.       创建数据库表

CREATE TABLE user
    (
      id int(11) NOT NULL PRIMARY KEY AUTO_INCREMENT,
      name varchar(255) DEFAULT NULL,
      password varchar(255) DEFAULT NULL
    );

3.       编写实体Bean

User.java

package com.wgb.bean.entity;
    
    import java.io.Serializable;
    
    import javax.persistence.Entity;
    import javax.persistence.EntityListeners;
    import javax.persistence.Id;
    
    import com.wgb.bean.UserListener;
    
    /** 
     * @className: User.java
     * @classDescription: 
     * @function: 
     * @author: Wentasy
     * @createTime: 2012-12-4 下午08:00:32
     * @modifyTime: 
     * @modifyReason: 
     * @since: JDK 1.6
     */
    @Entity
    @EntityListeners(UserListener.class)
    public class User implements Serializable{
    	private int id;
    	private String name;
    	private String password;
    	
    	@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;
    	}
    	public String getPassword() {
    		return password;
    	}
    	public void setPassword(String password) {
    		this.password = password;
    	}
    }

4.       创建对数据库进行操作的Session Bean

UserDao.java

package com.wgb.dao;
    
    import java.util.List;
    
    import com.wgb.bean.entity.User;
    
    /** 
     * @className: UserDao.java
     * @classDescription: 
     * @function: 
     * @author: Wentasy
     * @createTime: 2012-12-4 下午08:02:46
     * @modifyTime: 
     * @modifyReason: 
     * @since: JDK 1.6
     */
    public interface UserDao {
    	public List<User> getAllUser();
    	public void insert(String name, String password);
    	public void update(User user);
    	public void delete(int id);
    	public User getUser(int id);
    }

UserDaoImpl.java

package com.wgb.dao.impl;
    
    import java.util.Iterator;
    import java.util.List;
    
    import javax.ejb.Remote;
    import javax.ejb.Stateless;
    import javax.persistence.EntityManager;
    import javax.persistence.PersistenceContext;
    import javax.persistence.Query;
    
    import com.wgb.bean.entity.User;
    import com.wgb.dao.UserDao;
    
    /** 
     * @className: UserDaoImpl.java
     * @classDescription: 
     * @function: 
     * @author: Wentasy
     * @createTime: 2012-12-4 下午08:03:25
     * @modifyTime: 
     * @modifyReason: 
     * @since: JDK 1.6
     */
    @Stateless
    @Remote ({UserDao.class})
    public class UserDaoImpl{
    	@PersistenceContext
    	private EntityManager em;
    	
    	@SuppressWarnings("unchecked")
    	public List<User> getAllUser(){
    		return em.createQuery("from User").getResultList();
    	}
    	
    	public void insert(String name, String password){
    		User user = new User();
    		user.setName(name);
    		user.setPassword(password);
    		em.persist(user);
    	}
    	public void update(User user){
    		em.merge(user);
    	}
    	public void delete(int id){
    		em.remove(em.find(User.class, id));
    	}
    	public User getUser(int id){
    		return em.find(User.class, id);
    	}
    
    }

5.       编写对生命周期进行处理的Listener

UserListener.java

package com.wgb.bean;
    
    import javax.persistence.PostLoad;
    import javax.persistence.PostPersist;
    import javax.persistence.PostRemove;
    import javax.persistence.PostUpdate;
    import javax.persistence.PrePersist;
    import javax.persistence.PreRemove;
    import javax.persistence.PreUpdate;
    
    import com.wgb.bean.entity.User;
    
    /** 
     * @className: UserListener.java
     * @classDescription: 
     * @function: 
     * @author: Wentasy
     * @createTime: 2012-12-11 下午07:44:00
     * @modifyTime: 
     * @modifyReason: 
     * @since: JDK 1.6
     */
    public class UserListener {
    	
    	@PrePersist
    	public void prePersist(User user){
    		System.out.println("prePersist called!");
    	}
    	@PostPersist
    	public void postPersist(User user){
    		System.out.println("postPersist called!");
    	}
    	@PreRemove
    	public void preRemove(User user){
    		System.out.println("preRemove called!");
    	}
    	@PostRemove
    	public void postRemove(User user){
    		System.out.println("postRemove called!");
    	}
    	@PreUpdate
    	public void preUpdate(User user){
    		System.out.println("preUpdate called!");
    	}
    	@PostUpdate
    	public void postUpdate(User user){
    		System.out.println("postUpdate called!");
    	}
    	@PostLoad
    	public void postLoad(User user){
    		System.out.println("postLoad called!");
    	}
    }

6.       编写显示页面

index.jsp

<%@ page language="java" import="java.util.*,javax.naming.*,com.wgb.bean.*,com.wgb.bean.entity.*,com.wgb.dao.*,com.wgb.dao.impl.*" pageEncoding="UTF-8"%> <% String path = request.getContextPath(); String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; %> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <base href="<%=basePath%>"> <title>My JSP 'index.jsp' starting page</title> <meta http-equiv="pragma" content="no-cache"> <meta http-equiv="cache-control" content="no-cache"> <meta http-equiv="expires" content="0"> <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"> <meta http-equiv="description" content="This is my page">  </head> <body> <% try { //Remote //Properties props = new Properties(); //props.setProperty("java.naming.factory.initial", "org.jnp.interfaces.NamingContextFactory"); //props.setProperty("java.naming.provider.url", "localhost:1099"); //props.setProperty("java.naming.factory.url.pkgs", "org.jboss.naming"); //InitialContext ctx = new InitialContext(props); //HelloWorld helloworld = (HelloWorld) ctx.lookup("HelloWorldBean/remote"); //out.print(helloworld.sayHello("WGB")); //Local InitialContext ctx = new InitialContext(); //HelloWorld helloworld = (HelloWorld) ctx.lookup("HelloWorldBean/local"); //out.print(helloworld.sayHello("Wentasy")); //MyTimer t = (MyTimer)ctx.lookup("MyTimerBean/local"); //t.start(); UserDao userDao = (UserDao)ctx.lookup("UserDaoImpl/remote"); //插入数据 //userDao.insert("123", "123"); //19:55:05,370 INFO [STDOUT] prePersist called! //19:55:05,496 INFO [STDOUT] postPersist called! //更新数据 //User user = new User(); //user.setId(4); //user.setName("125"); //user.setPassword("123"); //userDao.update(user); //19:55:26,769 INFO [STDOUT] postLoad called! //19:55:26,770 INFO [STDOUT] preUpdate called! //19:55:26,775 INFO [STDOUT] postUpdate called! //删除数据 //userDao.delete(6); //19:56:37,074 INFO [STDOUT] postLoad called! //19:56:37,078 INFO [STDOUT] preRemove called! //19:56:37,083 INFO [STDOUT] postRemove called! //得到所有数据 //for (User u : userDao.getAllUser()) { // out.println(u.getId() + " : " + u.getName() + "<br/>"); //} //19:57:28,970 INFO [STDOUT] postLoad called! //19:57:28,970 INFO [STDOUT] postLoad called! //19:57:28,970 INFO [STDOUT] postLoad called! //19:57:28,971 INFO [STDOUT] postLoad called! //得到单条数据 //User u = userDao.getUser(1); //out.println(u.getId() + " : " + u.getName() + " : " + u.getPassword()); //19:58:09,524 INFO [STDOUT] postLoad called! } catch (NamingException e) { e.printStackTrace(); } %> </body> </html>

### 生命周期探讨 ###

![1355302975_1549.png][]

![1355302979_6904.jpg][]

插入数据

调用prePersist和postPersist

更新数据

调用postLoad、preUpdate和postUpdate

删除数据

调用postLoad、preUpdate和postUpdate

得到所有数据

调用四次postLoad，因有四条数据

得到单条数据

调用一次postLoad

[1355302975_1549.png]: https://img-my.csdn.net/uploads/201212/12/1355302975_1549.png
[1355302979_6904.jpg]: https://img-my.csdn.net/uploads/201212/12/1355302979_6904.jpg