这里有jpa的很多例子 http://www.objectdb.com/java/jpa/persistence/store 是很好的学习资料
开发环境:myeclipse 10.0
服务器:tomcat 6.0
oracle:11g
hibernate版本:4.2.4
1.新建名为JpaWeb的web工程 添加依赖的jar包 添加配置文件 详细步骤前面博客已有提到 这里就不说了
persistence.xml
<persistence xmlns="http://java.sun.com/xml/ns/persistence"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd"
version="2.0">
<persistence-unit name="under">
<properties>
<property name="hibernate.connection.driver_class" value="oracle.jdbc.driver.OracleDriver"/>
<property name="hibernate.connection.username" value="under_test" />
<property name="hibernate.connection.password" value="under_test" />
<property name="hibernate.connection.url" value="jdbc:oracle:thin:@localhost:1521:ganew" />
<property name="hibernate.hbm2ddl.auto" value="update" />
<property name="hibernate.show_sql" value="true" />
<property name="hibernate.dialect" value="org.hibernate.dialect.Oracle10gDialect" />
</properties>
</persistence-unit>
</persistence>
2.修改index.jsp文件 如下:
<%@page import="com.bean.Vistor"%>
<%@ page language="java" import="java.util.*" pageEncoding="gbk"%>
<%
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">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
<script type="text/javascript">
function check()
{
if(document.getElementById("nameid").value=="") { alert('姓名不能为空'); return false;}
if(document.getElementById("hobbyid").value=="") { alert('爱好不能为空'); return false;}
document.getElementById("vis").submit();
}
</script>
</head>
<body>
<form method="post" action="<%=request.getContextPath() %>/DealCommit" id="vis">
姓名:<input type="text" name="name" id="nameid"> <br/>
爱好:<input type="text" name="hobby" id="hobbyid"><br/>
<input type="button" value="提交" onclick="check();">
</form>
<hr/>
<ol>
<%
List<Vistor> list=(List<Vistor>)request.getAttribute("list");
if(list!=null) {
for(Vistor vistor:list) { %>
<li><%=vistor %></li>
<%}
}%>
</ol>
</body>
</html>
上面页面有一个表单 用户可以输入姓名和爱好 提交到servlet之后 会将系统中所有登陆的记录全部显示在界面上
DealCommit的servlet实现
packagecom.undergrowth;
importjava.io.IOException;
importjava.io.PrintWriter;
importjava.util.List;
importjavax.persistence.EntityManager;
importjavax.persistence.EntityManagerFactory;
importjavax.persistence.Query;
importjavax.servlet.ServletException;
importjavax.servlet.http.HttpServlet;
importjavax.servlet.http.HttpServletRequest;
importjavax.servlet.http.HttpServletResponse;
importcom.bean.Vistor;
public classDealCommit extends HttpServlet {
/**
* Constructor of theobject.
*/
public DealCommit() {
super();
}
/**
* Destruction of theservlet. <br>
*/
public void destroy(){
super.destroy(); //Just puts "destroy" string in log
// Put your code here
}
/**
* The doGet method ofthe servlet. <br>
*
* This method iscalled when a form has its tag value method equals to get.
*
* @param request therequest send by the client to the server
* @param response theresponse send by the server to the client
* @throwsServletException if an error occurred
* @throws IOExceptionif an error occurred
*/
public voiddoGet(HttpServletRequest request, HttpServletResponse response)
throwsServletException, IOException {
request.setCharacterEncoding("gbk");
EntityManagerFactoryfactory=(EntityManagerFactory)getServletContext().getAttribute("factory");
EntityManagermanager=factory.createEntityManager();
try {
Stringname=request.getParameter("name");
Stringhobby=request.getParameter("hobby");
manager.getTransaction().begin();
manager.persist(newVistor(name, hobby));
manager.getTransaction().commit();
//获取所有记录
Queryquery=manager.createQuery("select v from Vistor v");
List<Vistor>list=query.getResultList();
request.setAttribute("list",list);
request.getRequestDispatcher("/index.jsp").forward(request,response);
} catch (Exception e){
e.printStackTrace();
}finally{
manager.close();
}
}
/**
* The doPost methodof the servlet. <br>
*
* This method iscalled when a form has its tag value method equals to post.
*
* @param request therequest send by the client to the server
* @param response theresponse send by the server to the client
* @throwsServletException if an error occurred
* @throws IOExceptionif an error occurred
*/
public voiddoPost(HttpServletRequest request, HttpServletResponse response)
throwsServletException, IOException {
this.doGet(request,response);
}
/**
* Initialization ofthe servlet. <br>
*
* @throwsServletException if an error occurs
*/
public void init()throws ServletException {
// Put your code here
}
}
在上面的servlet中 从应用程序级别获取了factory对象 因为在应用web启动的时候 注册了一个servletcontextlistener的实现类 这个实现类就是在应用启动时 初始化了一个factory的实例 存入了应用程序的属性中
并且将用户提交的姓名还有爱好存入的数据库中 并且将数据库中已有的对象全部查询出来 返回给index.jsp页面显示
JpaListener的监听器代码如下:
应用启动的时候 获取EntityManagerFactory实例存入application的属性中 应用关闭的时候 关闭EntityManagerFactory的实例
packagecom.undergrowth;
importjavax.persistence.EntityManagerFactory;
importjavax.persistence.Persistence;
importjavax.servlet.ServletContextEvent;
importjavax.servlet.ServletContextListener;
public classJpaListener implements ServletContextListener {
@Override
public voidcontextDestroyed(ServletContextEvent arg0) {
// TODOAuto-generated method stub
EntityManagerFactoryfactory=(EntityManagerFactory)arg0.getServletContext().getAttribute("factory");
factory.close();
}
@Override
public voidcontextInitialized(ServletContextEvent arg0) {
// TODO Auto-generatedmethod stub
EntityManagerFactoryfactory=Persistence.createEntityManagerFactory("under");
arg0.getServletContext().setAttribute("factory",factory);
}
}
当然 还需要在web.xml中加入监听器的配置项 如下:
<listener>
<listener-class>com.undergrowth.JpaListener</listener-class>
</listener>
再来看看这里的实体对象 Vistor的实现代码:
package com.bean;
import java.util.Date;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Lob;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;
@Entity
public class Vistor {
@Id @GeneratedValue
private Integer id;
@Column(length=12,nullable=false)
private String name;
@Lob
private String hobby;
@Temporal(TemporalType.TIMESTAMP)
private Date loginTime=new Date(System.currentTimeMillis());
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getHobby() {
return hobby;
}
public void setHobby(String hobby) {
this.hobby = hobby;
}
public Date getLoginTime() {
return loginTime;
}
public void setLoginTime(Date loginTime) {
this.loginTime = loginTime;
}
public Vistor(){}
public Vistor(String name, String hobby) {
super();
this.name = name;
this.hobby = hobby;
}
@Override
public String toString() {
return name + " " + hobby
+ " " + loginTime.toLocaleString();
}
}
index.jsp效果图:
