前提概要

Mapper接口开发方法只需要程序员编写Mapper接口（相当于Dao接口），由Mybatis框架根据接口定义创建接口的动态代理对象，代理对象的方法体同上边Dao接口实现类方法。

Mapper接口开发需要遵循以下规范：

1.Mapper.xml文件中的namespace与mapper接口的类路径相同。

2.Mapper接口方法名和Mapper.xml中定义的每个statement的id相同

3.Mapper接口方法的输入参数类型和mapper.xml中定义的每个sql 的parameterType的类型相同

4.Mapper接口方法的输出参数类型和mapper.xml中定义的每个sql的resultType的类型相同

下面是实例介绍。

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1.环境配置

工程目录结构如下

SqlMapConfig.xml

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2.Mapper映射接口（UserMapper.java)和Mapper映射表(UserMapper.xml)

UserMapper.java

package com.pwc.dao.mapper;import java.util.List;import com.pwc.pojo.User;public interface UserMapper {
         public User findById(int id);    public void deleteById(int id);    public void insert(User user);    public List
     
       findByAge(int age);}
     

UserMapper.xml

     
         
              SELECT * FROM User WHERE id = #{id}        
      
               INSERT INTO User(name,age) VALUES(#{name},#{age})    
          
      
               DELETE * FROM User WHERE id=#{id}    
          
              SELECT * FROM User WHERE age=#{age}    
     

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3.测试

测试类

package com.pwc.test;import org.apache.ibatis.session.SqlSession;import org.apache.ibatis.session.SqlSessionFactory;import org.apache.ibatis.session.SqlSessionFactoryBuilder;import com.pwc.dao.mapper.UserMapper;import com.pwc.pojo.User;public class Test {    public static void main(String[] args) {        SqlSessionFactoryBuilder builder=new SqlSessionFactoryBuilder();        SqlSessionFactory factory=builder.build(Test.class.getClassLoader().getResourceAsStream("SqlMapConfig.xml"));        SqlSession session = factory.openSession();        UserMapper mapper = session.getMapper(UserMapper.class);        User user = mapper.findById(1);        session.close();        System.out.println(user);    }}

测试结果如下

User [id=1, name=pwc, age=18]

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