一步步实现:JPA的基本增删改查CRUD(jpa基于hibernate)
1.创建一个JPA工程
首先,创建一个JPA工程(若不知道JPA创建或出现at least one user library must be selected等错误,请参考http://blog.****.net/baidu_37107022/article/details/76554393)
jar包说明
2.创建实体类
有关实体类中相关注解的说明
- * @Table 标注类对应的表
- * 若表名和类型相同时,省略@Table,比如类Users 和表 users;
- * 若不相同时,必须有@Table,并设置name,为该类对应的表名。@Table(name="users")
- *
- * @Entity 标注实体
- *
- * @Id 标注id
- *
- * @Transient 标注该属性不做与表的映射(原因:可能表中没有该属性对应的字段)
- * 有该注解,在执行sql语句时,就不会出现该属性,否则会有,若表中没有该字段则会报错
- *
- * @Basic 默认所有属性都有该注解(主键需要单独使用@Id),所以可以省略
- * 该注解可以放在属性上,也可以放在对应的getter方法上。
- * 注意:要么统一将@Basic放在属性上,要么统一放在对应的getter方法上。(一般都放在属性上,可读性比较好)
- *
- * @Column 类中属性名和表中对应字段名不相同时,会使用该注解,指明在类中对应的字段
- * @Column(name="对应的表中字段名")
构建实体类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 标注类对应的表
- * 若表名和类型相同时,省略@Table,比如类Users 和表 users;
- * 若不相同时,必须有@Table,并设置name,为该类对应的表名。@Table(name="users")
- *
- * @Entity 标注实体
- *
- * @Id 标注id
- *
- * @Transient 标注该属性不做与表的映射(原因:可能表中没有该属性对应的字段)
- * 有该注解,在执行sql语句时,就不会出现该属性,否则会有,若表中没有该字段则会报错
- *
- * @Basic 默认所有属性都有该注解(主键需要单独使用@Id),所以可以省略
- * 该注解可以放在属性上,也可以放在对应的getter方法上。
- * 注意:要么统一将@Basic放在属性上,要么统一放在对应的getter方法上。(一般都放在属性上,可读性比较好)
- *
- * @Column 类中属性名和表中对应字段名不相同时,会使用该注解,指明在类中对应的字段
- * @Column(name="对应的表中字段名")
- *
- */
- @Table(name="users")
- @Entity
- public class Users {
- //标注id
- @Id
- private String uid;
- @Basic
- @Column(name="uname")
- private String uname;
- @Basic
- private int age;
- @Transient
- private String remark;//备注
- 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;
- }
- @Override
- public 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产品 -->
- <provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
- <!-- 添加对应的持久化类 -->
- <class>com.java.bean.Users</class>
- <properties>
- <!-- jpa中连接数据库 -->
- <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基本属性 -->
- <property name="hibernate.show_sql" value="true" />
- <property name="hibernate.format_sql" value="true" />
- </properties>
- </persistence-unit>
- </persistence>
4.测试增删改查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 {
- // 插入数据 persist 相当于hibernate save方法
- public void testInsert() {
- // 1.获得Factory
- EntityManagerFactory factory = Persistence.createEntityManagerFactory("JPA");
- // 2.获取Manager
- EntityManager manager = factory.createEntityManager();
- // 3.获得事务,并开启uiwu
- EntityTransaction transaction = manager.getTransaction();
- transaction.begin();
- // 4.执行sql
- Users users = new Users("1", "小明", 18);
- manager.persist(users);
- // 5.提交事务,关闭资源
- transaction.commit();
- manager.close();
- factory.close();
- }
- /**
- * 创建EntityManagerFactory的第二种方式 可以将如下配置放在创建factory是进行配置,使用map
- * <property name="hibernate.show_sql" value="true" /> <property name=
- * "hibernate.format_sql" value="true" />
- *
- * 当配置文件中和创建factory时有同一配置时,会按照创建的factory中的设置执行
- */
- public void testInsert2() {
- // 1.获得Factory
- Map properties = new HashMap<String, Object>();
- properties.put("hibernate.format_sql", "false");
- EntityManagerFactory factory = Persistence.createEntityManagerFactory("JPA", properties);
- // 2.获取Manager
- EntityManager manager = factory.createEntityManager();
- // 3.获得事务,并开启uiwu
- EntityTransaction transaction = manager.getTransaction();
- transaction.begin();
- // 4.执行sql
- Users users = new Users("2", "小明2", 18);
- manager.persist(users);
- // 5.提交事务,关闭资源
- transaction.commit();
- manager.close();
- factory.close();
- }
- // 根据id查询 find 相当于hibernate get方法
- public void testFind() {
- // 1.获得Factory
- EntityManagerFactory factory = Persistence.createEntityManagerFactory("JPA");
- // 2.获取Manager
- EntityManager manager = factory.createEntityManager();
- // 3.获得事务,并开启事务
- EntityTransaction transaction = manager.getTransaction();
- transaction.begin();
- // 4.执行sql
- Users users = manager.find(Users.class, "1");
- System.out.println(users);
- // 5.提交事务,关闭资源
- transaction.commit();
- manager.close();
- factory.close();
- }
- // 根据id查询 getReference 相当于hibernate load方法
- // find和getReference的区别----与hibernate中get和load的区别一样---懒加载--id没有对应值时报异常
- public void testGet() {
- // 1.获得Factory
- EntityManagerFactory factory = Persistence.createEntityManagerFactory("JPA");
- // 2.获取Manager
- EntityManager manager = factory.createEntityManager();
- // 3.获得事务,并开启事务
- EntityTransaction transaction = manager.getTransaction();
- transaction.begin();
- // 4.执行sql
- Users users=manager.getReference(Users.class, "1");
- System.out.println(users);
- // 5.提交事务,关闭资源
- transaction.commit();
- manager.close();
- factory.close();
- }
- // 修改数据
- public void testUpdate() {
- // 1.获得Factory
- EntityManagerFactory factory = Persistence.createEntityManagerFactory("JPA");
- // 2.获取Manager
- EntityManager manager = factory.createEntityManager();
- // 3.获得事务,并开启事务
- EntityTransaction transaction = manager.getTransaction();
- transaction.begin();
- // 4.执行sql
- Users users=manager.find(Users.class, "1");
- users.setUname("哈哈哈1");
- // 5.提交事务,关闭资源
- transaction.commit();
- manager.close();
- factory.close();
- }
- // 删除数据 remove 相当于hibernate delete方法
- // remove方法只能移除执久化对象,不能删除游离对象
- public void testRemove() {
- // 1.获得Factory
- EntityManagerFactory factory = Persistence.createEntityManagerFactory("JPA");
- // 2.获取Manager
- EntityManager manager = factory.createEntityManager();
- // 3.获得事务,并开启事务
- EntityTransaction transaction = manager.getTransaction();
- transaction.begin();
- // 4.执行sql
- Users users=manager.find(Users.class, "2"); manager.remove(users);
- // 5.提交事务,关闭资源
- transaction.commit();
- manager.close();
- factory.close();
- }
- }
1.创建一个JPA工程
首先,创建一个JPA工程(若不知道JPA创建或出现at least one user library must be selected等错误,请参考http://blog.****.net/baidu_37107022/article/details/76554393)
jar包说明
2.创建实体类
有关实体类中相关注解的说明
- * @Table 标注类对应的表
- * 若表名和类型相同时,省略@Table,比如类Users 和表 users;
- * 若不相同时,必须有@Table,并设置name,为该类对应的表名。@Table(name="users")
- *
- * @Entity 标注实体
- *
- * @Id 标注id
- *
- * @Transient 标注该属性不做与表的映射(原因:可能表中没有该属性对应的字段)
- * 有该注解,在执行sql语句时,就不会出现该属性,否则会有,若表中没有该字段则会报错
- *
- * @Basic 默认所有属性都有该注解(主键需要单独使用@Id),所以可以省略
- * 该注解可以放在属性上,也可以放在对应的getter方法上。
- * 注意:要么统一将@Basic放在属性上,要么统一放在对应的getter方法上。(一般都放在属性上,可读性比较好)
- *
- * @Column 类中属性名和表中对应字段名不相同时,会使用该注解,指明在类中对应的字段
- * @Column(name="对应的表中字段名")
构建实体类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 标注类对应的表
- * 若表名和类型相同时,省略@Table,比如类Users 和表 users;
- * 若不相同时,必须有@Table,并设置name,为该类对应的表名。@Table(name="users")
- *
- * @Entity 标注实体
- *
- * @Id 标注id
- *
- * @Transient 标注该属性不做与表的映射(原因:可能表中没有该属性对应的字段)
- * 有该注解,在执行sql语句时,就不会出现该属性,否则会有,若表中没有该字段则会报错
- *
- * @Basic 默认所有属性都有该注解(主键需要单独使用@Id),所以可以省略
- * 该注解可以放在属性上,也可以放在对应的getter方法上。
- * 注意:要么统一将@Basic放在属性上,要么统一放在对应的getter方法上。(一般都放在属性上,可读性比较好)
- *
- * @Column 类中属性名和表中对应字段名不相同时,会使用该注解,指明在类中对应的字段
- * @Column(name="对应的表中字段名")
- *
- */
- @Table(name="users")
- @Entity
- public class Users {
- //标注id
- @Id
- private String uid;
- @Basic
- @Column(name="uname")
- private String uname;
- @Basic
- private int age;
- @Transient
- private String remark;//备注
- 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;
- }
- @Override
- public 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产品 -->
- <provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
- <!-- 添加对应的持久化类 -->
- <class>com.java.bean.Users</class>
- <properties>
- <!-- jpa中连接数据库 -->
- <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基本属性 -->
- <property name="hibernate.show_sql" value="true" />
- <property name="hibernate.format_sql" value="true" />
- </properties>
- </persistence-unit>
- </persistence>
4.测试增删改查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 {
- // 插入数据 persist 相当于hibernate save方法
- public void testInsert() {
- // 1.获得Factory
- EntityManagerFactory factory = Persistence.createEntityManagerFactory("JPA");
- // 2.获取Manager
- EntityManager manager = factory.createEntityManager();
- // 3.获得事务,并开启uiwu
- EntityTransaction transaction = manager.getTransaction();
- transaction.begin();
- // 4.执行sql
- Users users = new Users("1", "小明", 18);
- manager.persist(users);
- // 5.提交事务,关闭资源
- transaction.commit();
- manager.close();
- factory.close();
- }
- /**
- * 创建EntityManagerFactory的第二种方式 可以将如下配置放在创建factory是进行配置,使用map
- * <property name="hibernate.show_sql" value="true" /> <property name=
- * "hibernate.format_sql" value="true" />
- *
- * 当配置文件中和创建factory时有同一配置时,会按照创建的factory中的设置执行
- */
- public void testInsert2() {
- // 1.获得Factory
- Map properties = new HashMap<String, Object>();
- properties.put("hibernate.format_sql", "false");
- EntityManagerFactory factory = Persistence.createEntityManagerFactory("JPA", properties);
- // 2.获取Manager
- EntityManager manager = factory.createEntityManager();
- // 3.获得事务,并开启uiwu
- EntityTransaction transaction = manager.getTransaction();
- transaction.begin();
- // 4.执行sql
- Users users = new Users("2", "小明2", 18);
- manager.persist(users);
- // 5.提交事务,关闭资源
- transaction.commit();
- manager.close();
- factory.close();
- }
- // 根据id查询 find 相当于hibernate get方法
- public void testFind() {
- // 1.获得Factory
- EntityManagerFactory factory = Persistence.createEntityManagerFactory("JPA");
- // 2.获取Manager
- EntityManager manager = factory.createEntityManager();
- // 3.获得事务,并开启事务
- EntityTransaction transaction = manager.getTransaction();
- transaction.begin();
- // 4.执行sql
- Users users = manager.find(Users.class, "1");
- System.out.println(users);
- // 5.提交事务,关闭资源
- transaction.commit();
- manager.close();
- factory.close();
- }
- // 根据id查询 getReference 相当于hibernate load方法
- // find和getReference的区别----与hibernate中get和load的区别一样---懒加载--id没有对应值时报异常
- public void testGet() {
- // 1.获得Factory
- EntityManagerFactory factory = Persistence.createEntityManagerFactory("JPA");
- // 2.获取Manager
- EntityManager manager = factory.createEntityManager();
- // 3.获得事务,并开启事务
- EntityTransaction transaction = manager.getTransaction();
- transaction.begin();
- // 4.执行sql
- Users users=manager.getReference(Users.class, "1");
- System.out.println(users);
- // 5.提交事务,关闭资源
- transaction.commit();
- manager.close();
- factory.close();
- }
- // 修改数据
- public void testUpdate() {
- // 1.获得Factory
- EntityManagerFactory factory = Persistence.createEntityManagerFactory("JPA");
- // 2.获取Manager
- EntityManager manager = factory.createEntityManager();
- // 3.获得事务,并开启事务
- EntityTransaction transaction = manager.getTransaction();
- transaction.begin();
- // 4.执行sql
- Users users=manager.find(Users.class, "1");
- users.setUname("哈哈哈1");
- // 5.提交事务,关闭资源
- transaction.commit();
- manager.close();
- factory.close();
- }
- // 删除数据 remove 相当于hibernate delete方法
- // remove方法只能移除执久化对象,不能删除游离对象
- public void testRemove() {
- // 1.获得Factory
- EntityManagerFactory factory = Persistence.createEntityManagerFactory("JPA");
- // 2.获取Manager
- EntityManager manager = factory.createEntityManager();
- // 3.获得事务,并开启事务
- EntityTransaction transaction = manager.getTransaction();
- transaction.begin();
- // 4.执行sql
- Users users=manager.find(Users.class, "2"); manager.remove(users);
- // 5.提交事务,关闭资源
- transaction.commit();
- manager.close();
- factory.close();
- }
- }