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。
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二、这里用OpenJPA 2.0 和Spring 3.0作为例子
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三、搭建Spring 和 JPA的框架步骤
1.搭建Spring3.0框架，然后Finish。
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2.然后搭建JPA框架，这里选用OpenJPA2.0版本
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Next
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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
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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
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2.映射实体，选择JPA的反向工程
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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。
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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"value="E276-JPA" /></bean><bean id="transactionManager" ref="entityManagerFactory" /></bean><!-- dao --><bean id="employeeDao" ref="entityManagerFactory" /></bean><!-- 注解式事务的配置 --><tx:annotation-driven transaction-manager="transactionManager" /></beans>
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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);}}?
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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;@Beforepublic void setUp() throws Exception {manager = EntityManagerHelper.getEntityManager();// 开始事务EntityManagerHelper.beginTransaction();}@Afterpublic 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nullEmployee 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());}}}?
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九、demo
E276-JPA.zip