1.創(chuàng)建一個(gè)JPA工程

首先，創(chuàng)建一個(gè)JPA工程（若不知道JPA創(chuàng)建或出現(xiàn)at least one user library must be selected等錯(cuò)誤，請(qǐng)參考http://blog.csdn.net/baidu_37107022/article/details/76554393）

jar包說明

2.創(chuàng)建實(shí)體類

有關(guān)實(shí)體類中相關(guān)注解的說明

* @Table 標(biāo)注類對(duì)應(yīng)的表* 若表名和類型相同時(shí)，省略@Table,比如類Users 和表 users;* 若不相同時(shí)，必須有@Table，并設(shè)置name,為該類對(duì)應(yīng)的表名。@Table(name="users")* * @Entity 標(biāo)注實(shí)體* * @Id 標(biāo)注id* * @Transient 標(biāo)注該屬性不做與表的映射(原因：可能表中沒有該屬性對(duì)應(yīng)的字段)* 有該注解，在執(zhí)行sql語句時(shí)，就不會(huì)出現(xiàn)該屬性，否則會(huì)有，若表中沒有該字段則會(huì)報(bào)錯(cuò)* * @Basic 默認(rèn)所有屬性都有該注解(主鍵需要單獨(dú)使用@Id)，所以可以省略* 該注解可以放在屬性上，也可以放在對(duì)應(yīng)的getter方法上。* 注意：要么統(tǒng)一將@Basic放在屬性上，要么統(tǒng)一放在對(duì)應(yīng)的getter方法上。（一般都放在屬性上，可讀性比較好）* * @Column 類中屬性名和表中對(duì)應(yīng)字段名不相同時(shí)，會(huì)使用該注解，指明在類中對(duì)應(yīng)的字段* @Column(name="對(duì)應(yīng)的表中字段名")

構(gòu)建實(shí)體類Users

import javax.persistence.Basic; import javax.persistence.Column; import javax.persistence.Entity; import javax.persistence.Id; import javax.persistence.Table; import javax.persistence.Transient; /*** @Table 標(biāo)注類對(duì)應(yīng)的表* 若表名和類型相同時(shí)，省略@Table,比如類Users 和表 users;* 若不相同時(shí)，必須有@Table，并設(shè)置name,為該類對(duì)應(yīng)的表名。@Table(name="users")* * @Entity 標(biāo)注實(shí)體* * @Id 標(biāo)注id* * @Transient 標(biāo)注該屬性不做與表的映射(原因：可能表中沒有該屬性對(duì)應(yīng)的字段)* 有該注解，在執(zhí)行sql語句時(shí)，就不會(huì)出現(xiàn)該屬性，否則會(huì)有，若表中沒有該字段則會(huì)報(bào)錯(cuò)* * @Basic 默認(rèn)所有屬性都有該注解(主鍵需要單獨(dú)使用@Id)，所以可以省略* 該注解可以放在屬性上，也可以放在對(duì)應(yīng)的getter方法上。* 注意：要么統(tǒng)一將@Basic放在屬性上，要么統(tǒng)一放在對(duì)應(yīng)的getter方法上。（一般都放在屬性上，可讀性比較好）* * @Column 類中屬性名和表中對(duì)應(yīng)字段名不相同時(shí)，會(huì)使用該注解，指明在類中對(duì)應(yīng)的字段* @Column(name="對(duì)應(yīng)的表中字段名")**/ @Table(name="users") @Entity public class Users {//標(biāo)注id@Idprivate String uid;@Basic@Column(name="uname")private String uname;@Basicprivate int age;@Transientprivate String remark;//備注public String getRemark() {return remark;}public void setRemark(String remark) {this.remark = remark;}public String getUid() {return uid;}public void setUid(String uid) {this.uid = uid;}public String getUname() {return uname;}public void setUname(String uname) {this.uname = uname;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}@Overridepublic String toString() {return "Users [uid=" + uid + ", uname=" + uname + ", age=" + age + "]";}public Users(String uid, String uname, int age) {super();this.uid = uid;this.uname = uname;this.age = age;}public Users() {super();// TODO Auto-generated constructor stub}}

3.JPA的配置文件persistence.xml的配置

<?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="JPA" transaction-type="RESOURCE_LOCAL"><!-- 配置jpa ORM產(chǎn)品 --><provider>org.hibernate.jpa.HibernatePersistenceProvider</provider><!-- 添加對(duì)應(yīng)的持久化類 --><class>com.java.bean.Users</class><properties><!-- jpa中連接數(shù)據(jù)庫 --><property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver" /><property name="javax.persistence.jdbc.url" value="jdbc:mysql://localhost:3306/jpa" /><property name="javax.persistence.jdbc.user" value="root" /><property name="javax.persistence.jdbc.password" value="123"></property><!-- jpa中配置hibernate基本屬性 --><property name="hibernate.show_sql" value="true" /><property name="hibernate.format_sql" value="true" /></properties></persistence-unit> </persistence>

4.測(cè)試增刪改查CRUD

import java.util.HashMap; import java.util.Map;import javax.persistence.EntityManager; import javax.persistence.EntityManagerFactory; import javax.persistence.EntityTransaction; import javax.persistence.Persistence;import com.java.utils.JPAUtils;import junit.framework.TestCase;public class TestUsers extends TestCase {// 插入數(shù)據(jù) persist 相當(dāng)于hibernate save方法public void testInsert() {// 1.獲得FactoryEntityManagerFactory factory = Persistence.createEntityManagerFactory("JPA");// 2.獲取ManagerEntityManager manager = factory.createEntityManager();// 3.獲得事務(wù)，并開啟uiwuEntityTransaction transaction = manager.getTransaction();transaction.begin();// 4.執(zhí)行sqlUsers users = new Users("1", "小明", 18);manager.persist(users);// 5.提交事務(wù)，關(guān)閉資源transaction.commit();manager.close();factory.close();}/*** 創(chuàng)建EntityManagerFactory的第二種方式 可以將如下配置放在創(chuàng)建factory是進(jìn)行配置，使用map* <property name="hibernate.show_sql" value="true" /> <property name=* "hibernate.format_sql" value="true" />* * 當(dāng)配置文件中和創(chuàng)建factory時(shí)有同一配置時(shí)，會(huì)按照創(chuàng)建的factory中的設(shè)置執(zhí)行*/public void testInsert2() {// 1.獲得FactoryMap properties = new HashMap<String, Object>();properties.put("hibernate.format_sql", "false");EntityManagerFactory factory = Persistence.createEntityManagerFactory("JPA", properties);// 2.獲取ManagerEntityManager manager = factory.createEntityManager();// 3.獲得事務(wù)，并開啟uiwuEntityTransaction transaction = manager.getTransaction();transaction.begin();// 4.執(zhí)行sqlUsers users = new Users("2", "小明2", 18);manager.persist(users);// 5.提交事務(wù)，關(guān)閉資源transaction.commit();manager.close();factory.close();}// 根據(jù)id查詢 find 相當(dāng)于hibernate get方法public void testFind() {// 1.獲得FactoryEntityManagerFactory factory = Persistence.createEntityManagerFactory("JPA");// 2.獲取ManagerEntityManager manager = factory.createEntityManager();// 3.獲得事務(wù)，并開啟事務(wù)EntityTransaction transaction = manager.getTransaction();transaction.begin();// 4.執(zhí)行sqlUsers users = manager.find(Users.class, "1");System.out.println(users);// 5.提交事務(wù)，關(guān)閉資源transaction.commit();manager.close();factory.close();}// 根據(jù)id查詢 getReference 相當(dāng)于hibernate load方法// find和getReference的區(qū)別----與hibernate中g(shù)et和load的區(qū)別一樣---懶加載--id沒有對(duì)應(yīng)值時(shí)報(bào)異常public void testGet() {// 1.獲得FactoryEntityManagerFactory factory = Persistence.createEntityManagerFactory("JPA");// 2.獲取ManagerEntityManager manager = factory.createEntityManager();// 3.獲得事務(wù)，并開啟事務(wù)EntityTransaction transaction = manager.getTransaction();transaction.begin();// 4.執(zhí)行sqlUsers users=manager.getReference(Users.class, "1"); System.out.println(users);// 5.提交事務(wù)，關(guān)閉資源transaction.commit();manager.close();factory.close();}// 修改數(shù)據(jù)public void testUpdate() {// 1.獲得FactoryEntityManagerFactory factory = Persistence.createEntityManagerFactory("JPA");// 2.獲取ManagerEntityManager manager = factory.createEntityManager();// 3.獲得事務(wù)，并開啟事務(wù)EntityTransaction transaction = manager.getTransaction();transaction.begin();// 4.執(zhí)行sqlUsers users=manager.find(Users.class, "1"); users.setUname("哈哈哈1");// 5.提交事務(wù)，關(guān)閉資源transaction.commit();manager.close();factory.close();}// 刪除數(shù)據(jù) remove 相當(dāng)于hibernate delete方法// remove方法只能移除執(zhí)久化對(duì)象，不能刪除游離對(duì)象public void testRemove() {// 1.獲得FactoryEntityManagerFactory factory = Persistence.createEntityManagerFactory("JPA");// 2.獲取ManagerEntityManager manager = factory.createEntityManager();// 3.獲得事務(wù)，并開啟事務(wù)EntityTransaction transaction = manager.getTransaction();transaction.begin();// 4.執(zhí)行sqlUsers users=manager.find(Users.class, "2"); manager.remove(users);// 5.提交事務(wù)，關(guān)閉資源transaction.commit();manager.close();factory.close();}}

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