02.Mybatis的动态代理方式实现增删改查

动态代理的方式实现增删改查:

通过约定的方式定位sql语句

约定 > 配置文件 > 硬编码

约定的目标是省略掉通过硬编码的方式定位sql的代码，通过接口直接定位出sql语句,以下代码为通过硬编码的方法定位sql:

 　　　　　//读取conf.xml 配置文件
         Reader reader = Resources.getResourceAsReader("conf.xml");
         //创建sqlSessionFactory
         SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(reader);
         //创建session---> connection
         SqlSession session = sessionFactory.openSession();
         //statement ---> statement
         String sql = "com.offcn.entity.personMapper." + "selectPersonById";
         //查询一条数据
         Person person = session.selectOne(sql,1);
         //提交事务
         session.commit();
         System.out.println(person);
         //关闭连接
         session.close();

通过约定的方式定位sql:

  Reader reader = Resources.getResourceAsReader("conf.xml");
 //创建一个sqlSessionFactory
 SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(reader);
 //创建一个sqlSession
 SqlSession session = sessionFactory.openSession();
 //用sqlSession定位sql
 PersonMapper personMapper = session.getMapper(PersonMapper.class);
 //通过接口中的方法找到sql语句并执行
 Person person = personMapper.queryPersonById(3);
 //提交事务
 session.commit();
 System.out.println(person);
 //关闭连接
 session.close();    

接口定义的规则:

1.方法名和mapper.xml文件中标签的id值相同

2.方法的输入参数类型和mapper.xml文件中标签的parameterType类型一致

3.方法的返回值和mapper.xml文件中标签的resultType类型一致

定义接口的代码如下:

 package com.offcn.mapper;

 import java.util.List;

 import com.offcn.entity.Person;

 public interface PersonMapper {
     Person queryPersonById(int id);
     List<Person> queryAllPersons();
     void insertPerson(Person person);
     void deletePersonById(int id);
     void updatePersonById(Person person);
 }

接口和映射文件的对应关系图示:

匹配过程;(约定的过程)

1.根据接口名找到mapper.xml文件(根据的是namespace=接口的全类名)

2.根据接口的方法名找到mapper.xml文件中的sql标签(方法名=sql标签中的id值)

以上两点可以保证当调用接口中的方法时，程序能自动定位到某一个Mapper.xml文件中的sql标签

习惯:sql映射文件（mapper.xml）和接口放在同一个包中

具体实现:

1.实体类代码:

 package com.offcn.entity;

 import java.util.Date;

 public class Person {
     private int id;
     private String name;
     private Date dir;
     private String address;
     public Person() {
         super();
         // TODO Auto-generated constructor stub
     }public Person( String name, Date dir, String address) {
         this.name = name;
         this.dir = dir;
         this.address = address;
     }
     public Person(int id, String name, Date dir, String address) {
         super();
         this.id = id;
         this.name = name;
         this.dir = dir;
         this.address = address;
     }
     public int getId() {
         return id;
     }
     public void setId(int id) {
         this.id = id;
     }
     public String getName() {
         return name;
     }
     public void setName(String name) {
         this.name = name;
     }
     public Date getDir() {
         return dir;
     }
     public void setDir(Date dir) {
         this.dir = dir;
     }
     public String getAddress() {
         return address;
     }
     public void setAddress(String address) {
         this.address = address;
     }
     @Override
     public String toString() {
         return "Person [id=" + id + ", name=" + name + ", dir=" + dir + ", address=" + address + "]";
     }

 }

2.映射文件mapper.xml代码:

 <?xml version="1.0" encoding="UTF-8"?>
 <!DOCTYPE mapper
   PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
   "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
 <mapper namespace="com.offcn.mapper.PersonMapper">
     <!-- 根据id查询 -->
   <select id="queryPersonById" parameterType="int" resultType="com.offcn.entity.Person">
     select * from person where id = #{id}
   </select>
   <!-- 查询所有 -->
   <select id="queryAllPersons"  resultType="com.offcn.entity.Person">
     select * from person
   </select>
   <!-- 增加 -->
   <insert id="insertPerson" parameterType="com.offcn.entity.Person">
       insert into person (name,bir,address) value (#{name},#{dir},#{address})
   </insert>
   <!-- 删除 -->
   <delete id="deletePersonById" parameterType="int">
       delete from person where id = #{id}
   </delete>
   <!-- 修改 -->
   <update id="updatePersonById" parameterType="com.offcn.entity.Person">
       update person set name = #{name},bir = #{dir},address = #{address} where id = #{id}
   </update>
 </mapper>

3.接口代码:

 package com.offcn.mapper;
 import java.util.List;
 import com.offcn.entity.Person;
 public interface PersonMapper {
     Person queryPersonById(int id);
     List<Person> queryAllPersons();
     void insertPerson(Person person);
     void deletePersonById(int id);
     void updatePersonById(Person person);
 }

4.全局配置文件conf.xml：

 <?xml version="1.0" encoding="UTF-8"?>
 <!DOCTYPE configuration
   PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
   "http://mybatis.org/dtd/mybatis-3-config.dtd">
 <configuration>
   <environments default="development">
     <environment id="development">
       <transactionManager type="JDBC"/>
       <dataSource type="POOLED">
         <property name="driver" value="com.mysql.jdbc.Driver"/>
         <property name="url" value="jdbc:mysql://localhost:3306/person?serverTimezone=UTC"/>
         <property name="username" value="root"/>
         <property name="password" value="root"/>
       </dataSource>
     </environment>
   </environments>
   <mappers>
     <mapper resource="com/offcn/mapper/personMapper.xml"/>
   </mappers>
 </configuration>

5.测试类代码:

 package com.offcn.test;

 import java.io.IOException;
 import java.io.Reader;
 import java.util.Date;
 import java.util.List;

 import org.apache.ibatis.io.Resources;
 import org.apache.ibatis.session.SqlSession;
 import org.apache.ibatis.session.SqlSessionFactory;
 import org.apache.ibatis.session.SqlSessionFactoryBuilder;

 import com.offcn.entity.Person;
 import com.offcn.mapper.PersonMapper;

 public class Test {
     public static void main(String[] args) throws IOException {
         //queryPersonById();
         //insertPerson();
         //deletePerson();
         updatePerosnById();
         queryAllPersons();
     }
     //根据id查询
     public static void queryPersonById() throws IOException {
         //读取conf.xml文件
         Reader reader = Resources.getResourceAsReader("conf.xml");
         //创建一个sqlSessionFactory
         SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(reader);
         //创建一个sqlSession
         SqlSession session = sessionFactory.openSession();
         //用sqlSession定位sql
         PersonMapper personMapper = session.getMapper(PersonMapper.class);
         //通过接口中的方法找到sql语句并执行
         Person person = personMapper.queryPersonById(3);
         //提交事务
         session.commit();
         System.out.println(person);
         //关闭连接
         session.close();
     }
     //查询所有的方法
     public static void queryAllPersons() throws IOException {
         //读取conf.xml文件
         Reader reader = Resources.getResourceAsReader("conf.xml");
         //创建sqlSessionFactory
         SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(reader);
         //创建一个sqlSession
         SqlSession session = sessionFactory.openSession();
         //通过session定位映射文件
         PersonMapper personMapper = session.getMapper(PersonMapper.class);
         //通过接口中的方法定位sql语句并执行
         List<Person> persons = personMapper.queryAllPersons();
         //提交事务
         session.commit();
         for (Person person : persons) {
             System.out.println(person);
         }
         //关闭连接
         session.close();
     }
     //增加的方法
     public static void insertPerson() throws IOException {
         //读取conf.xml文件
         Reader reader = Resources.getResourceAsReader("conf.xml");
         //创建sqlSessionFactory
         SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(reader);
         //创建sqlSession
         SqlSession session = sessionFactory.openSession();
         //通过sqlSession定位映射文件
         PersonMapper personMapper = session.getMapper(PersonMapper.class);
         //通过接口中的方法定位sql语句
         Person person = new Person("王大拿",new Date(),"天津");
         personMapper.insertPerson(person);
         //提交事务
         session.commit();
         System.out.println("增加成功");
         //关闭连接
         session.close();
     }
     //删除的方法
     public static void deletePerson() throws IOException {
         //读取conf.xml
         Reader reader = Resources.getResourceAsReader("conf.xml");
         //创建一个sqlSessionFactory
         SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(reader);
         //创建一个sqlSession
         SqlSession session = sessionFactory.openSession();
         //通过session定位映射文件
         PersonMapper personMapper = session.getMapper(PersonMapper.class);
         //通过接口中的方法定位sql语句
         personMapper.deletePersonById(1);
         //提交事务
         session.commit();
         System.out.println("删除成功");
         //关闭连接
         session.close();
     }
     //修改的方法
     public static void updatePerosnById() throws IOException {
         //读取conf.xml
         Reader reader = Resources.getResourceAsReader("conf.xml");
         //创建sqlSessionFactory
         SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(reader);
         //创建一个sqlSession
         SqlSession session = sessionFactory.openSession();
         //通过sqlSession定位樱色号文件
         PersonMapper personMapper = session.getMapper(PersonMapper.class);
         //通过接口中的方法定位sql
         Person person = new Person(3,"张三",new Date(),"江苏");
         personMapper.updatePersonById(person);
         //提交事务
         session.commit();
         System.out.println("修改成功");
         session.close();
     }
 }

需要注意的注意事项:

在全局配置文件conf.xml文件中,引入配置文件的方式有四种，常用以下两种:

第一种:

<mapper resource="com/offcn/mapper/studentMapper.xml"/>

第二种：（要求接口和映射文件必须在同一个包下而且必须同名）

<package name="com.offcn.mapper"/>

常见错误: