[大数据]MyBatis接口代理方式 (主流)

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接下来用代码来实现

首先编写一个接口mapper

package com.cong.dao;

import com.cong.domain.User;

import java.util.List;

public interface UserMapper {
    public List<User> findAll();
}

然后编写映射文件 注意的是: mapper接口要对应 id要对应方法名?

resultType="user"对应输出的实体对应名 

parameterType=""输入参数也要对应 对应findAll("parameterType"),这了没有参数所以就没有写

<?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.cong.dao.UserMapper">
<!--    查询所有-->
    <select id="findAll" resultType="user">
        select * from tb_user
    </select>
</mapper>

然后写一个service层调用dao层

package com.cong.service;

import com.cong.dao.UserMapper;
import com.cong.domain.User;
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 java.io.IOException;
import java.io.InputStream;
import java.util.List;

public class UserService {
    public static void main(String[] args) throws IOException {
        InputStream resourceAsStream = Resources.getResourceAsStream("mybatis-config.xml");
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);
        SqlSession sqlSession = sqlSessionFactory.openSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        List<User> all = mapper.findAll();
        System.out.println(all);
    }
}

编写一个带参数的查询 注意输入参数int 和输出参数user

findById

<!--    根据id查询实体-->
    <select id="findById" parameterType="int" resultType="user">
        select * from tb_user where id=#{id}
    </select>

编写接口 注意对应参数

    public User findById(int id);

测试

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