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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建立一個新的JPA project:
Platform選擇EclipseLink,作為JPA的provider之一。
在Eclipse裡自動產生的project如所示:
用下列xml的內容覆蓋自動產生的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>
建立一個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 @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; }}
現在可以寫測試程式了:
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"); }}
成功執行後,在PostgreSQL的Admin UI上能看到測試Java程式裡用JPA插入資料庫的記錄:
本文完整的原始碼和所需的庫檔案可以在我的github上找到。
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使用JPA + Eclipselink操作PostgreSQL資料庫