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 |