JavaSE中Jpa的应用入门

JavaSE中Jpa的应用入门

一.   JPa提供的用户接口

 

Persistence,EntityMangerFactory,EntityManager

二.   配置.

1．添加Jar包

以hibernate作为Jpa的实现进行.

添加hibernate的jar包.

添加hibernate-entitymanager的jar包

2.配置persistence.xml文件

在src下新建文件夹META-INF

在MET-INF创建persistence.xml文件.配置如下:

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

<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_1_0.xsd" version="1.0">

   

    <persistence-unit name="Emp" transaction-type="RESOURCE_LOCAL">

       <provider>org.hibernate.ejb.HibernatePersistence</provider>

       <class>org.jenfer.jpa.entity.Emp</class>

        <properties>

           <property name = "hibernate.connection.driver_class" value = "com.mysql.jdbc.Driver"/>

           <property name = "hibernate.connection.url" value = "jdbc:mysql://localhost/test"/>

           <property name = "hibernate.connection.username" value = "root"/>

           <property name = "hibernate.connection.password" value = "fox"/>

           <property name = "hibernate.hbm2ddl.auto" value="update"/>

          

           <property name="hibernate.show_sql" value="true"/>

        </properties>

    </persistence-unit>

</persistence>

说明: persistence-unit是持久化单元的名字

< provider/>:JPA实现提供程序

<class/>持久化的类

<properties/> 实现厂商自定义的属性

                           这里是hibernate的自定属性.相关资料参考hibernate的配置

三.   实体类的实现:

以下是是用Jpa的注解的POJO.

@Table,@Entity等请参考Jpa官方文档

 

@Table(name = "emp")

@Entity(name = "Emp")

public class Emp {

    @Id

    @Column(name = "emp_id")

    @GeneratedValue(strategy = GenerationType.IDENTITY)

    private int empId;

 

    @Column(name = "emp_name", length = 10)

    private String empName;

 

    private String email;

 

    /**

     * Default constructor

     */

    public Emp() {

    }

 

    public int getEmpId() {

       return empId;

    }

 

    public void setEmpId(int empId) {

       this.empId = empId;

    }

 

    public String getEmpName() {

       return empName;

    }

 

    public void setEmpName(String empName) {

       this.empName = empName;

    }

 

    public String getEmail() {

       return email;

    }

 

    public void setEmail(String email) {

       this.email = email;

    }

}

 

四.   测试类库的编写.用到Junit测试框架

public class EvnTest {

    private static EntityManager manager;

 

    @BeforeClass

    public static void init() {

       EntityManagerFactory factory = Persistence

              .createEntityManagerFactory("Emp");

       manager = factory.createEntityManager();

    }

 

    @AfterClass

    public static void destory(){

       if(manager!=null){

           manager.close();

       }

    }

   

    @Test

    @Ignore

    public void envTest() {

 

       Emp emp = new Emp();

       emp.setEmail("[e-mail]");

       emp.setEmpName("周星驰");

       EntityTransaction tx = manager.getTransaction();

       try {

           tx.begin();

           manager.persist(emp);

           tx.commit();

       } catch (Exception e) {

           tx.rollback();

       }

    }

 

    @Test@Ignore

    public void queryTest() {

       Emp emp=manager.find(Emp.class, 1);

       System.out.println(emp.getEmpName());

    }

   

    @Test@Ignore

    public void updateTest(){

       Emp emp = new Emp();

       emp.setEmail("[e-mail]");

       emp.setEmpName("周剑华");

       emp.setEmpId(1);

      

       EntityTransaction tx = manager.getTransaction();

       try {

           tx.begin();

           manager.<Emp>merge(emp);

           tx.commit();

       }