开发第一个openjpa应用

概述

     openJPA是完全基于sun 公司的JPA规范而开发的，不像Hibernate，TopLink等其他JPA产品还有一套自己的应用规则。JPA是包含于EJB 3.0规范中的，JPA相当于EJB的persistence bean与dao。我在这里就不多废话了，只记录JPA相关的内容。

 

第一个应用

 

首先我们在eclipse中创建一个名为JPA的项目。并加入相应的包文件。这些包文件可以从http://openjpa.apache.org/ 获得。

 

1、在项目的src目录中需要创建一个META-INF目录，此目录是必需的（至少我是这么做的），并且在META-INF目录添加persistence.xml文件，内容如下：

<persistence xmlns="http://java.sun.com/xml/ns/persistence"


	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" version="1.0">


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


		<!-- ORM 类 -->


		<class>model.Person</class>


		<properties>


			<property name="openjpa.ConnectionDriverName" value="com.mysql.jdbc.Driver" />


			<property name="openjpa.ConnectionURL" value="jdbc:mysql://localhost:3306/test?characterEncoding=utf8" />


			<property name="openjpa.jdbc.DBDictionary" value="mysql"/>


			<property name="openjpa.ConnectionUserName" value="root"/>


			<property name="openjpa.ConnectionPassword" value="123456"/>


			<property name="openjpa.FetchBatchSize" value="20"/>


			<!-- 配置从java ORM annotation 生成数据库结构，配置此步时，需要把对应的java ORM类复制上面的<class/>标签中。 -->


			<property name="openjpa.jdbc.SynchronizeMappings" value="buildSchema(ForeignKeys=true,PrimaryKeys=true,Indexes=true,schemaAction=refresh)"/>


		</properties>


	</persistence-unit>


</persistence>

2、在model包先后添加如下文件：Gender.java、Person.java，它们的内容如下：

package model;





public enum Gender {


	WOMAN,


	MAN


}

package model;





import java.util.Date;





import javax.persistence.Column;


import javax.persistence.Entity;


import javax.persistence.EnumType;


import javax.persistence.Enumerated;


import javax.persistence.GeneratedValue;


import javax.persistence.GenerationType;


import javax.persistence.Id;


import javax.persistence.Temporal;


import javax.persistence.TemporalType;





@Entity


public class Person extends BaseObject {





	


	private static final long serialVersionUID = 2970135183705353062L;


	


	@Id


	@GeneratedValue(strategy = GenerationType.IDENTITY)


	private Integer id;


	


	@Column(length = 20, nullable = false)


	private String name;





	@Temporal(TemporalType.DATE)


	@Column(nullable = false)


	private Date birthday;





	@Enumerated(EnumType.STRING)


	@Column(nullable = false,columnDefinition=" enum('man','woman') NOT NULL DEFAULT 'man' ")


	private Gender gender = Gender.MAN;





	public String getName() {


		return name;


	}





	public void setName(String name) {


		this.name = name;


	}





	public Date getBirthday() {


		return birthday;


	}





	public void setBirthday(Date birthday) {


		this.birthday = birthday;


	}





	public Gender getGender() {


		return gender;


	}





	public void setGender(Gender gender) {


		this.gender = gender;


	}





	public Integer getId() {


		return id;


	}





	public void setId(Integer id) {


		this.id = id;


	}





}

 

3、在test包中添加PersonTest.java文件，内容如下：

package test;





import java.util.Date;





import javax.persistence.EntityManager;


import javax.persistence.EntityManagerFactory;


import javax.persistence.Persistence;





import junit.framework.TestCase;


import model.Person;





public class PersonTest extends TestCase {





	public void testSave() {


		EntityManagerFactory factory = Persistence


				.createEntityManagerFactory("mysql_jpa");


		EntityManager em = factory.createEntityManager();


		em.getTransaction().begin();


		Person p = new Person();


		p.setName("林某某");


		p.setBirthday(new Date());


		em.persist(p);


		em.getTransaction().commit();


		em.close();


		factory.close();


	}





	public void testFind() {


		EntityManagerFactory factory = Persistence


				.createEntityManagerFactory("mysql_jpa");


		EntityManager em = factory.createEntityManager();


		String jpql = "select count(p.id) from Person as p where 1=1 and p.name like ?1";


		System.out.println(em.createQuery(jpql).setParameter(1, "%林%").getSingleResult());


		em.close();


		factory.close();


	}


}

 4、右键PersonTest.java -> Run as -> Run configurations，在配置运行配置页中配置如下。

然后在以下VM arguments位置添加AspectJ的参数“-javaagent:${workspace_loc:JPA}/lib/openjpa-2.0.0-beta.jar”，如下图：

 

5、记录创建一个数据库，我是用test为名称。

6、运行Junit，输出消息如下：

 

78  mysql_jpa  INFO   [main] openjpa.Runtime - Starting OpenJPA 2.0.0-beta
156  mysql_jpa  INFO   [main] openjpa.jdbc.JDBC - Using dictionary class "org.apache.openjpa.jdbc.sql.MySQLDictionary".
1140  mysql_jpa  WARN   [main] openjpa.jdbc.Schema - Existing column "gender" on table "person" is incompatible with the same column in the given schema definition. Existing column:
Full Name: person.gender
Type: char
Size: 5
Default: man
Not Null: true
Given column:
Full Name: Person.gender
Type: varchar
Size: 255
Default: null
Not Null: true

16  mysql_jpa  INFO   [main] openjpa.Runtime - Starting OpenJPA 2.0.0-beta
16  mysql_jpa  INFO   [main] openjpa.jdbc.JDBC - Using dictionary class "org.apache.openjpa.jdbc.sql.MySQLDictionary".
78  mysql_jpa  WARN   [main] openjpa.jdbc.Schema - Existing column "gender" on table "person" is incompatible with the same column in the given schema definition. Existing column:
Full Name: person.gender
Type: char
Size: 5
Default: man
Not Null: true
Given column:
Full Name: Person.gender
Type: varchar
Size: 255
Default: null
Not Null: true

328  mysql_jpa  INFO   [main] openjpa.Runtime - Query "select count(p.id) from Person as p where 1=1 and p.name like ?1" is removed from cache excluded permanentlybecause this query returns a single value rather than a list. A query that returns single value can not be cached. .
5

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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