首先確保您已經安裝了PostgreSQL。您可以參考我這篇文章PostgreSQL掃盲教程。

使用Eclipse創建一個新的JPA project：

Platform選擇EclipseLink，作為JPA的provider之一。

在Eclipse里自動生成的project如下圖所示：

用下列xml的內容覆蓋自動生成的xml：

<?xml version="1.0" encoding="UTF-8"?> <persistence version="2.0" 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_2_0.xsd"><persistence-unit name="jerryjpa" transaction-type="RESOURCE_LOCAL"><provider>org.eclipse.persistence.jpa.PersistenceProvider</provider><class>jpatest.Person</class><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>

新建一個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@GeneratedValueprivate long id;@Basicprivate String firstName;@Basicprivate 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;} }

現在可以寫測試程序了：

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");} }

成功執行后，在PostgreSQL的Admin UI上能看到測試Java程序里用JPA插入數據庫的記錄：

本文完整的源代碼和所需的庫文件可以在我的github上找到。

• eclipselink-2.5.1.jar

• javax.persistence-2.1.0.jar

• postgresql-42.1.1.jar

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