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("[email protected]");
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("[email protected]");
emp.setEmpName("周剑华");
emp.setEmpId(1);
EntityTransaction tx = manager.getTransaction();
try {
tx.begin();
manager.<Emp>merge(emp);
tx.commit();
}