转载1. 1.本文主要技术采用了Servlet + JSP + EJB 3.0 + JPA，开发环境用的是EclipseHelios + JDK 1.6 + JBOSS 5.1 + MySQL 5.1数据库。
2. 2. 示例场景：用户通过Web页面对Employee进行创建、查找和删除。这个小例子重点是演示JPA的使用。JPA是JavaPersistence API的缩写，主要是将液正关系晌埋尘数据库的操作对象化，它的j2ee的标准规范，由于其自身简单易用的优点，也是SAP推荐使用的数据库技术。
3. 3.准备工作：
(1) 安装JBOSS 5.1
(2) 安装MySQL 5.1
(3) 给Jboss配置数据源
首先启动mysql后，创建一个数据库叫ejbtest，然后创建一个用户jboss，密码是password，并将ejbtest的权限赋给它。
然后在路径jboss-5.1.0.GA/server/default/deploy下放入mysql-ds.xml文件。
Mysql-ds.xml:
<datasources>
<local-tx-datasource>
<jndi-name>MySqlDS</jndi-name>
<connection-url>jdbc:mysql://localhost:3306/ejbtest</connection-url>
<driver-class>com.mysql.jdbc.Driver</driver-class>
<user-name>jboss</user-name>
<password>password</password>
</local-tx-datasource>
</datasources>
4. 4.开发
4.1先创建一个EJB Project，名字叫EmployeeEJB。
然后在META-INF目录下新建一个persistence.xml文件
4.2开始创建我们的Entity Bean：Employee类，它是一个简单的Java Bean。
package com.sap.demo.ejb.employee.model;
import javax.persistence.Entity;
import javax.persistence.Id;
@Entity
public class Employee {
@Id
privateint id;
publicint getId() {
returnid;
}
publicvoid setId(int id) {
this.id= id;
}
publicString getName() {
returnname;
}
publicvoid setName(String name) {
this.name= name;
}
privateString name;
}
4.3 在ejb项目中创建一个Local的SessionBean，名字叫EmployeeServicel，它的主要功能是对employee进行数据的操作，宴禅包括创建、查找、删除。
接口声明：
package com.sap.demo.ejb.employee.ejb;
import javax.ejb.Local;
importcom.sap.demo.ejb.employee.model.Employee;
@Local
public interface EmployeeServiceLocal {
publicEmployee createEmployee(int id, String name);
publicEmployee findEmployee(int id);
publicvoid deleteEmployee(int id);
}
这里是接口的实现：
package com.sap.demo.ejb.employee.ejb;
import javax.ejb.Stateless;
import javax.ejb.TransactionAttribute;
import javax.ejb.TransactionAttributeType;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
importcom.sap.demo.ejb.employee.model.Employee;
@Stateless
public class EmployeeService implementsEmployeeServiceLocal {
@PersistenceContext(unitName= "EmployeeDS")
privateEntityManager em;
@Override
publicEmployee createEmployee(int id, String name) {
Employeeemp = new Employee();
emp.setId(id);
emp.setName(name);
em.persist(emp);
returnemp;
}
@Override
@TransactionAttribute(TransactionAttributeType.SUPPORTS)
publicEmployee findEmployee(int id) {
returnem.find(Employee.class, new Integer(id));
}
@Override
publicvoid deleteEmployee(int id) {
Employeeemp = findEmployee(id);
if(emp != null) {
em.remove(emp);
}
}
}
这样EJB项目就创建完毕了。
4 4.4 然后创建Web Project，名字叫EmployeeWeb。这个项目很简单，包含一个Servlet和两个页面index.jsp和result.jsp。用户在index.jsp对employee进行创建、查找、删除，然后由result.jsp负责展示结果。
Index.jsp
<%@ pagelanguage="java" contentType="text/html;charset=ISO-8859-1"
pageEncoding="ISO-8859-1"%>
<!DOCTYPE htmlPUBLIC "-//W3C//DTDHTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type"content="text/html; charset=ISO-8859-1">
<title>Insert titlehere</title>
</head>
<body>
<FORM ACTION="ShowResult">
Id:
<INPUTTYPE="text" NAME="id"/><P>
Name:
<INPUTTYPE="TEXT" NAME="name"/>
<INPUTTYPE="hidden" NAME="method"VALUE="create" />
<INPUTTYPE="SUBMIT" VALUE="Createemployee and show result.">
</FORM>
<FORM ACTION="ShowResult">
Id:
<INPUTTYPE="text" NAME="id"/>
<inputTYPE="hidden" NAME="method"VALUE="find" />
<INPUTTYPE="SUBMIT" VALUE="Find employeeand show result.">
</FORM>
<FORM ACTION="ShowResult">
Id:
<INPUTTYPE="text" NAME="id"/>
<inputTYPE="hidden" NAME="method"VALUE="delete" />
<INPUTTYPE="SUBMIT" VALUE="Deleteemployee and show result.">
</FORM>
</body>
</html>
result.jsp
<%@ pagelanguage="java" contentType="text/html;charset=ISO-8859-1"
pageEncoding="ISO-8859-1"%>
<!DOCTYPE htmlPUBLIC "-//W3C//DTDHTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type"content="text/html; charset=ISO-8859-1">
<title>Insert titlehere</title>
</head>
<body>
<jsp:useBean id="employee"type="com.sap.demo.ejb.employee.model.Employee"scope="request"/>
id:<jsp:getProperty name="employee"property="id"/>,
name:<jsp:getProperty name="employee"property="name"/>
</body>
</html>
最后是Servlet ShowResult:
package com.sap.demo.ejb.servlets;
import java.io.IOException;
import javax.ejb.EJB;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
importjavax.servlet.http.HttpServletResponse;
import com.sap.demo.ejb.employee.ejb.EmployeeServiceLocal;
importcom.sap.demo.ejb.employee.model.Employee;
public class ShowResult extends HttpServlet {
privatestatic final long serialVersionUID = 1L;
@EJB
privateEmployeeServiceLocal service;
public ShowResult() {
super();
// TODO Auto-generated constructor stub
}
protectedvoid doGet(HttpServletRequest request, HttpServletResponse response) throwsServletException, IOException {
Stringmethod = request.getParameter("method");
if(method.equals("create")) {
Stringname = request.getParameter("name");
Stringids = request.getParameter("id");
intid = Integer.parseInt(ids);
Employeeem = service.createEmployee(id, name);
request.setAttribute("employee",em);
}elseif (method.equals("find")) {
Stringids = request.getParameter("id");
intid = Integer.parseInt(ids);
Employeeem = service.findEmployee(id);
request.setAttribute("employee",em);
}else if (method.equals("delete")){
Stringids = request.getParameter("id");
intid = Integer.parseInt(ids);
Employeeem = service.findEmployee(id);
if(em != null){
service.deleteEmployee(id);
request.setAttribute("employee",em);
}
}
RequestDispatcherdispatcher = request.getRequestDispatcher("result.jsp");
dispatcher.forward(request,response);
}
protectedvoid doPost(HttpServletRequest request, HttpServletResponse response) throwsServletException, IOException {
//TODO Auto-generated method stub
}
}
