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: