JPA和hibernate
1.JPA的概念一级它和hibernate之间的关系
JPA：它是java persistence api , java持久化ORM规范，hibernate实现了JAP规范。
2.JPA的环境搭建和入门案例
1.配置pom文件
<packaging>jar</packaging> <dependencies> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.11</version> <scope>test</scope> </dependency> <!-- 添加Hibernate依赖 --> <dependency> <groupId>org.hibernate</groupId> <artifactId>hibernate-core</artifactId> <version>5.4.10.Final</version> </dependency> <!-- 添加Log4J依赖 --> <dependency> <groupId>log4j</groupId> <artifactId>log4j</artifactId> <version>1.2.16</version> </dependency> <dependency> <groupId>org.slf4j</groupId> <artifactId>slf4j-nop</artifactId> <version>1.6.4</version> </dependency> <!-- 添加javassist --> <dependency> <groupId>javassist</groupId> <artifactId>javassist</artifactId> <version>3.12.0.GA</version> </dependency> <!-- mysql数据库的驱动包 --> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>5.1.6</version> </dependency> <!-- 配置hibernate的c3p0数据库连接池 --> <dependency> <groupId>org.hibernate</groupId> <artifactId>hibernate-c3p0</artifactId> <version>5.4.10.Final</version> </dependency> <!--实现JPA--> <dependency> <groupId>org.hibernate</groupId> <artifactId>hibernate-entitymanager</artifactId> <version>5.4.8.Final</version> </dependency> </dependencies>
2.配置persistence.md.xml主文件
需要注意的是加载文件的时候，会在类文件下的META-INF下面自动找。test01_hibernate03_jpa\src\main\resources\META-INF\persistence.xml
<?xml version="1.0" encoding="UTF-8" ?> <persistence 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_1_0.xsd" version="1.0"> <!--配置持久化单元(persistence-unit)，可以配置多个，名称不能重复 transaction-type:指定事务类型 JTA：java Transaction API 规范 RESOURCE_LOCAL:值本地的代码事务（一般都用这个） --> <persistence-unit name="myJPAUnit1" transaction-type="RESOURCE_LOCAL"> <!--JPA规范的提供商 可以不写--> <!--<provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>--> <!-- 指定由JPA注解的实体类位置 可以不写--> <!--<class>com.domain.Customer</class>--> <!-- 连接数据库配置，用的时hibernate的主配置--> <properties> <!-- 1.连接数据库的基本信息 --> <property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver"></property> <property name="hibernate.connection.url" value="jdbc:mysql://127.0.0.1:3306/mybatis"></property> <property name="hibernate.connection.username" value="root"></property> <property name="hibernate.connection.password" value="root"></property> <!-- 2.hibernate的可选配置 --> <!-- hibernate里的配置，数据库使用的方言，开发过程中要在控制台显示,sql --> <property name="hibernate.show_sql" value="true"></property> <property name="hibernate.format_sql" value="true"></property> <property name="hibernate.hbm2ddl.auto" value="update"></property> </properties> </persistence-unit> </persistence>
3.编写实体类
package com.domain; import org.hibernate.annotations.Target; import javax.persistence.*; import java.io.Serializable; import java.util.HashSet; import java.util.Set; /** * 客户实体类 * 使用注解时JPA规范，所以导包都需要导入javax.persistence下的包 */ @Entity //表明当前类是一个实体类 @Table(name = "jpa_customer") //建立与数据库表之间的联系 public class Customer implements Serializable { @Id //表明当前字段是主键 @Column(name = "c_id") //对应数据库中的字段名 @GeneratedValue(strategy =GenerationType.IDENTITY ) //使用JAP中的主键生成策略 private Integer id; @Column(name = "c_name") private String name; @Column(name = "c_lovel") private String lovel; }
4.编写工具了，运行，自动生成数据库表
import javax.persistence.EntityManager; import javax.persistence.EntityManagerFactory; import javax.persistence.Persistence; public class JPAUtils { //类似SessionFactory private static EntityManagerFactory factory; //加载配置文件 static { factory= Persistence.createEntityManagerFactory("myJPAUnit1"); } public static EntityManager createEntityManager(){ return factory.createEntityManager(); } //运行数据库表自动生成 public static void main(String[] args) { createEntityManager(); } }
5.CRUD测试
import com.domain.Customer; import com.utils.JPAUtils; import org.junit.Test; import javax.persistence.EntityManager; import javax.persistence.EntityTransaction; import javax.persistence.Query; import java.util.List; public class JPATest01 { //保存操作 persist() @Test public void Test01(){ Customer c=new Customer(); c.setName("曹操"); c.setLovel("实诚"); //1.获取EntityManager EntityManager em= JPAUtils.createEntityManager(); //2.获取事务开启事务 EntityTransaction tx = em.getTransaction(); tx.begin(); //3.执行保存操作，persist()方法 em.persist(c); //释放资源 tx.commit(); em.close(); } //查询单个实体操作 find()立即加载 @Test public void Test02_1(){ //1.获取EntityManager EntityManager em= JPAUtils.createEntityManager(); //2.获取事务开启事务 EntityTransaction tx = em.getTransaction(); tx.begin(); //3.查询出对象 Customer customer = em.find(Customer.class, 1); System.out.println("==========="); System.out.println(customer); //释放资源 tx.commit(); em.close(); } //查询单个实体操作 getReference()延迟加载 @Test public void Test02_2(){ //1.获取EntityManager EntityManager em= JPAUtils.createEntityManager(); //2.获取事务开启事务 EntityTransaction tx = em.getTransaction(); tx.begin(); //3.查询出对象 Customer customer = em.getReference(Customer.class, 1); System.out.println("==========="); System.out.println(customer); //释放资源 tx.commit(); em.close(); } //保存merge()用来和并对象保存数据库，以托管状态为主 @Test public void Test03(){ //1.获取EntityManager EntityManager em= JPAUtils.createEntityManager(); //2.获取事务开启事务 EntityTransaction tx = em.getTransaction(); tx.begin(); //3.查询出对象，快照保存 Customer customer = em.find(Customer.class, 1); System.out.println(customer); customer.setLovel("黄盖"); //快照保存 em.merge(customer); //释放资源 tx.commit(); em.close(); } //删除remove @Test public void Test04(){ //1.获取EntityManager EntityManager em= JPAUtils.createEntityManager(); //2.获取事务开启事务 EntityTransaction tx = em.getTransaction(); tx.begin(); //3.删除 Customer customer = em.find(Customer.class, 2); em.remove(customer); //释放资源 tx.commit(); em.close(); } //查询所有 @Test public void Test05(){ //1.获取EntityManager EntityManager em= JPAUtils.createEntityManager(); //2.获取事务开启事务 EntityTransaction tx = em.getTransaction(); tx.begin(); //3.获取Query对象 //sql不能用* 要用别名 Query query = em.createQuery("select c from Customer c"); List list = query.getResultList(); for (Object o : list) { System.out.println((Customer)o); } //释放资源 tx.commit(); em.close(); } //查询所有 有条件 @Test public void Test06(){ //1.获取EntityManager EntityManager em= JPAUtils.createEntityManager(); //2.获取事务开启事务 EntityTransaction tx = em.getTransaction(); tx.begin(); //3.获取Query对象 //sql 条件要使用‘？1’风格 Query query = em.createQuery("select c from Customer c where c.name like ?1 and c.lovel = ?2"); query.setParameter(1,"%曹%"); query.setParameter(2,"关爱兄弟"); List list = query.getResultList(); for (Object o : list) { System.out.println((Customer)o); } //释放资源 tx.commit(); em.close(); } }
