使用JPA + Eclipselink操作PostgreSQL数据库

首先确保您已经安装了PostgreSQL。您可以参考我这篇文章PostgreSQL扫盲教程。

使用Eclipse创建一个新的JPA project：

Platform选择EclipseLink，作为JPA的provider之一。

在Eclipse里自动生成的project如下图所示：

用下列xml的内容覆盖自动生成的xml：

xml version="1.0" encoding="UTF-8"?> <persistence version="2.0" xmlns="" xmlns:xsi="" xsi:schemaLocation=" /persistence_2_0.xsd"> <persistence-unit name="jerryjpa" transaction-type="RESOURCE_LOCAL"> <provider>org.eclipse.persistence.jpa.PersistenceProviderprovider> <class>jpatest.Personclass> <properties> <property name="eclipselink.ddl-generation" value="create-tables" /> <property name="javax.persistence.jdbc.url" value="jdbc:postgresql://localhost:5432/postgres"/> <property name="javax.persistence.jdbc.driver" value="org.postgresql.Driver"/> <property name="javax.persistence.jdbc.user" value="postgres"/> <property name="javax.persistence.jdbc.password" value="test_password"/> properties> persistence-unit> persistence> 

新建一个Java class:

 package jpatest; import javax.persistence.Basic; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.Id; import javax.persistence.NamedQuery; import javax.persistence.Table; @Entity @Table(name = "T_PERSON") @NamedQuery(name = "AllPersons", query = "select p from Person p") public class Person { @Id @GeneratedValue private long id; @Basic private String firstName; @Basic private String lastName; public long getId() { return id;
    } public void setId(long newId) { this.id = newId;
    } public String getFirstName() { return this.firstName;
    } public void setFirstName(String newFirstName) { this.firstName = newFirstName;
    } public String getLastName() { return this.lastName;
    } public void setLastName(String newLastName) { this.lastName = newLastName;
    }
} 

现在可以写测试程序了：

package jpatest; import javax.persistence.EntityManager; import javax.persistence.EntityManagerFactory; import javax.persistence.EntityTransaction; import javax.persistence.Persistence; public class Test { public static void main(String[] args) {
        
        String persistenceUnitName = "jerryjpa";  
        EntityManagerFactory factory = Persistence.createEntityManagerFactory(persistenceUnitName);  
        EntityManager entityManager = factory.createEntityManager();  
        EntityTransaction transaction = entityManager.getTransaction();  
        transaction.begin();  
       
        Person user = new Person();  
        user.setFirstName("Jerry_SAP");
        user.setLastName("Wang");
        entityManager.persist(user);  
        
        transaction.commit();  
        entityManager.close();  
        factory.close();  
        
        System.out.println("done");
    }
} 

成功执行后，在PostgreSQL的Admin UI上能看到测试Java程序里用JPA插入数据库的记录：

本文完整的源代码和所需的库文件可以在我的github上找到。

• eclipselink-2.5.1.jar

• javax.persistence-2.1.0.jar

• postgresql-42.1.1.jar

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