JavaSE使用JPA简单案例:

JavaSE使用JPA简单案例:

 

使用的JPA提供者是openjpa.


首先,新建一个普通的Java工程;

 

然后,导入openjpa所需要的jar包、数据库的驱动类、javaee.jar

 

(因为包含javax.persistence.*的API),见下图:

 

JavaSE使用JPA简单案例:

 

接着编写EntityBean:

 

package study.entity;

import javax.persistence.Id;

import java.io.Serializable;

import javax.persistence.*;

@SuppressWarnings("serial")
@Entity
public class Person implements Serializable{

	@Id
	@GeneratedValue(strategy=GenerationType.IDENTITY)
	private int id;
	
	private String name;

	public int getId() {
		return id;
	}

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

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}
}
 

然后是编写DAO吧,其实我更喜欢称为Service:

 

package study.service;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;

import study.entity.Person;

public class PersonManagerImpl implements PersonManager {

	@Override
	public Person getPerson(int personId) {

		EntityManagerFactory emf = Persistence
				.createEntityManagerFactory("helloworld");

		EntityManager manager = emf.createEntityManager();

		Person person = manager.find(Person.class, personId);

		manager.close();
		emf.close();
		return person;
	}

	@Override
	public void addPerson(Person person) {
		EntityManagerFactory emf = Persistence
				.createEntityManagerFactory("helloworld");

		EntityManager manager = emf.createEntityManager();
		manager.getTransaction().begin();
		manager.persist(person);
		manager.getTransaction().commit();
		
		manager.close();
		emf.close();
	}

}

 

在src下新建一个META-INF目录,在该目录中新建一个persistence.xml文件:

 

<?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="helloworld" transaction-type="RESOURCE_LOCAL">
		<provider>
             org.apache.openjpa.persistence.PersistenceProviderImpl
 	        </provider>
		<class>study.entity.Person</class>
		<properties>
			<property name="openjpa.ConnectionURL" value="jdbc:mysql://localhost/firstjpa" />
			<property name="openjpa.ConnectionDriverName" value="com.mysql.jdbc.Driver" />
			<property name="openjpa.ConnectionUserName" value="root" />
			<property name="openjpa.ConnectionPassword" value="XXXXXX" />
		</properties>

	</persistence-unit>

</persistence>

 因为使用的是 JAVASE,所以直接将连接信息,写在了文件中。如果是用EJB容器,则可以使用JNDI的方式。

 

 

 

最后,在数据库中新建相应的数据库、数据库的表

 

(如果是Hibernate的话,可以不用见表,OpenJpa暂时不明了,还是新建吧。)


JavaSE使用JPA简单案例:

 

测试类 (打错了,少了个t,写成Tes了   ⊙﹏⊙b汗):

package study.test;

import study.entity.Person;
import study.service.PersonManager;
import study.service.PersonManagerImpl;

public class Tes {

	public static void main(String[] args) {

		PersonManager manager = new PersonManagerImpl();
		
		Person person = new Person();
		person.setName("xiaolongfeixiang");
		manager.addPerson(person);
		
		
		Person person2 = manager.getPerson(1);
		System.out.println(person2.getName());
		
	}

}
 

运行结果:

 


JavaSE使用JPA简单案例:

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