Web编程学习五:使用Jersey和JPA来创建RESTfulWebService(一)

在上一个练习学习了如何使用Jersey，以及JAXB来创建RESTful的web service。

现在我来结合后台数据库对其做升级，也就是通过Jersey创建用来修改后台数据库的RESTful web service。

开发环境：

Eclipse Juno， 数据库MySQL 5.5， Jersey 1.18，EclipseLink 2.4, JAVA 1.6, 应用服务器Tomcat 7。

1.创建一个叫做jersey3的Dynamic Web Project。添加JPA的facet。

2.导入Jersey包，导入EclipseLink包，导入MySQL的connect包。

3.开发数据库对象，配置JPA。

数据对象Employee类：

package sample;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Table;
import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement
@Entity
@Table(name = "employee")
public class Employee {
	@Id
	@Column(name = "userId")
	private Long id;
	@Column(name = "firstName")
	private String firstName;
	@Column(name = "lastName")
	private String lastName;

	public long getId() {
		return id;
	}

	public void setId(long id) {
		this.id = id;
	}

	public String getFirstName() {
		return firstName;
	}

	public void setFirstName(String firstName) {
		this.firstName = firstName;
	}

	public String getLastName() {
		return lastName;
	}

	public void setLastName(String lastName) {
		this.lastName = lastName;
	}
}

< xml version="1.0" encoding="UTF-8" >

	
		org.eclipse.persistence.jpa.PersistenceProvider
		sample.Employee
		
			
			
			
			
		
	
 

4.配置Jersey，编写代码来实现RESTful web service。

创建web.xml:

< xml version="1.0" encoding="UTF-8" >    
    
  RestProjectTest    
     
    Jersey REST Service    
    com.sun.jersey.spi.container.servlet.ServletContainer    
        
      com.sun.jersey.config.property.packages    
      sample    
        
              
        com.sun.jersey.api.json.POJOMappingFeature    
        true    
            
    1    
      
      
    Jersey REST Service    
    /*    
      
  
        sample.LocalEntityManagerFactory  
      
   

注意添加了一个监听器LocalEntityManagerFactory，实现了ServletContextListener类，它可以在应用启动和关闭的时候后自动调用。

可以来管理我们的EntityManager。

package sample;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import javax.servlet.annotation.WebListener;

@WebListener
public class LocalEntityManagerFactory implements ServletContextListener {
	private static EntityManagerFactory emf;

	@Override
	public void contextInitialized(ServletContextEvent event) {
		emf = Persistence.createEntityManagerFactory("EmployeePU");
		
		System.out.println("ServletContextListener started");
	}

	@Override
	public void contextDestroyed(ServletContextEvent event) {
		emf.close();
		System.out.println("ServletContextListener destroyed");
	}

	public static EntityManager createEntityManager() {
		if (emf == null) {
			throw new IllegalStateException("Context is not initialized yet.");
		}
		return emf.createEntityManager();
	}
}

package sample;

import java.util.List;

import javax.persistence.EntityManager;
import javax.persistence.Query;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.PathParam;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;

@Path("/employee")
public class EmployeeController {
	@GET
	@Produces({ MediaType.TEXT_XML })
	@Path("{id}")