Spring-JPA，带一小例子

一、JPA简介：

       JPA全称Java Persistence API。JPA通过JDK 5.0注解或XML描述对象－关系表的映射关系，并将运行期的实体对象持久化到数据库中。

 

二、这里用OpenJPA 2.0 和Spring 3.0作为例子

 

三、搭建Spring 和 JPA的框架步骤

1.搭建Spring3.0框架，然后Finish。

 

2.然后搭建JPA框架，这里选用OpenJPA2.0版本

 

Next

 

选上所链接的数据库，还有数据库驱动，这里用的是Oracle数据库。接着Finish

 

 

四、框架搭建完成后，映射实体类

1.当框架搭建完之后，会在src目录下发现一个新建的文件夹和文件

 

2.映射实体，选择JPA的反向工程

 

勾上以下选项，会自动生成接口类，实现类，和工具类。接着Next就行了，和Hibernate的差不多。

 

 

五、Spring的配置文件

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:p="http://www.springframework.org/schema/p"
	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx.xsd"
	xmlns:tx="http://www.springframework.org/schema/tx">


	<bean id="entityManagerFactory"
		class="org.springframework.orm.jpa.LocalEntityManagerFactoryBean">
		<property name="persistenceUnitName" value="E276-JPA" />
	</bean>
	
	<bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
		<property name="entityManagerFactory" ref="entityManagerFactory" />
	</bean>

	<!-- dao -->
	<bean id="employeeDao" class="org.e276.dao.impl.EmployeeDAO">
		<property name="entityManagerFactory" ref="entityManagerFactory" />
	</bean>
	
	<!-- 注解式事务的配置 -->
	<tx:annotation-driven transaction-manager="transactionManager" />
	
</beans>

 

 

七、测试类

package org.e276.test;

import java.util.Date;
import java.util.List;
import org.e276.dao.IEmployeeDAO;
import org.e276.entity.Department;
import org.e276.entity.Employee;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Test {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
		// 注意这里的写法Spring 3.0不同
		IEmployeeDAO employeeDao = context.getBean(IEmployeeDAO.class);
		// 查询所有的员工
		List<Employee> employees = employeeDao.findAll();
		for (Employee employee : employees) {
			System.out.println("姓名：" + employee.getName() + "，性别：" + employee.getSex());
		}
		
		//添加新的员工
		Employee employee = new Employee(null, new Department((short) 5), "小屁孩", true, 1438d, new Date());
		employeeDao.save(employee);
	}

}

 

 

八、又或者添加单元测试框架来测试

package org.e276.test;

import java.util.Date;
import java.util.List;
import javax.persistence.EntityManager;
import org.e276.entity.Department;
import org.e276.entity.Employee;
import org.e276.util.EntityManagerHelper;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

public class TestEmployee {

	// 得到EntityManager对象
	EntityManager manager = null;

	@Before
	public void setUp() throws Exception {
		manager = EntityManagerHelper.getEntityManager();
		// 开始事务
		EntityManagerHelper.beginTransaction();
	}

	@After
	public void tearDown() throws Exception {
		// 提交事务
		EntityManagerHelper.commit();
		EntityManagerHelper.closeEntityManager();
	}

	public void saveEmployee() {
		Department department = new Department((short) 2);
		// 因为主键是通过序列产生，所以一定要设置成null
		Employee employee = new Employee(null, department, "李培翔", true, 4500d, new Date());
		manager.persist(employee);
		System.out.println(employee.getName() + "添加成功！");
	}

	public void findEmployee() {
		Employee employee = manager.find(Employee.class, 1004);
		System.out.println("找到一只小伙伴：" + employee.getName());
	}

	public void deleteEmployee() {
		Employee employee = manager.find(Employee.class, 1005);
		manager.remove(employee);
		System.out.println("含泪忍痛删掉一小伙伴，他名字是：" + employee.getName());
	}

	public void updateEmployee() {
		Employee employee = manager.find(Employee.class, 1);
		employee.setSalary(15000d);
		manager.merge(employee);
	}

	/**
	 * 查询某部门的员工人数
	 */
	public void findDepartmentCount() {
		// JPA-QL不支持*号
		Long count = (Long) manager
				.createQuery("select count(e) from Employee e where e.department.name=:name")
				.setParameter("name", "生产部").getSingleResult();
		System.out.println("生产部的人数是：" + count);
	}

	/**
	 * 查询某个部门的所有员工
	 */
	@Test
	@SuppressWarnings("unchecked")
	public void findEmployeeByDepartment() {
		List<Employee> list = manager
				.createQuery("select e from Employee e where e.department.name=:name")
				.setParameter("name", "生产部").getResultList();
		for (Employee employee : list) {
			System.out.println(employee.getName() + "工资：" + employee.getSalary());
		}
	}
}

 

 

九、demo

E276-JPA.zip