Mybatis获取参数的几种方式

Mybatis获取参数的几种方式

这里以UserDao实现User类的方法为例，以代码及注释的方式展现

package com.qcw.mybatis.mapper;

import com.qcw.mybatis.pojo.User;
import org.apache.ibatis.annotations.Param;

import java.util.Map;

/**
 *mybatis获取参数的几种方式：#{}和${}
 * -对于一下几种获取参数的方法可直接归结为两种：体类类型的参数 和 参数上设置@param注解
 * 前三种方法都可以用第四种方法实现更为简便
 *
 * 1.若mapper接口方法的参数为单个的字面量类型，此时可以通过#{},${}以任意内容获取参数值
 *
 * 2.若mapper接口方法的参数为多个字面量类型
 *   -此时mybatis会将参数放在map集合，以两种方式存储数据，
 *   -以arg0,arg1...为键，以参数为值;或者以param1，param2...为键，以参数为值
 *   -因此，只需要通过#{}，${}访问map集合的键,来获取相应的值
 *
 * 3.若mapper接口方法的参数为map集合类型的参数，
 *   -只需要通过#{}，${}访问map集合的键,就可以获取相应的值
 *
 * 4.若mapper接口方法的参数为实体类类型的参数
 *   -只需要通过#{}，${}访问实体类中的属性名，就可以获取相应的值
 *
 * 5.可以在mapper接口方法的参数上设置@param注解，此时mybatis会将这些参数放在map中
 * 以两种方式进行存储 (相比2，3两种方法更为简便,所以更建议使用代替前三种方法)
 *   -以@param注解的value值为键，以参数为值，或者以param1，param2..为键，以参数为值
 */
public interface UserMapper {

    //根据用户名查询用户信息
    User getUserByUsername(String username);

    //验证登录
    User checkLogin(String username, String password);

    //验证登录(以map集合来作为参数)
    User checkLoginByMap(Map<String,Object> map);

    //添加用户信息
    void insertUser(User user);

    //验证登录，使用@Param注解
    User checkLoginByParam(@Param("username") String username, @Param("password") String password);
}

<?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.qcw.mybatis.mapper.UserMapper">

    <select id="getUserByUsername" resultType="User">
        select * from t_user where username = #{username}
    </select>


    <select id="checkLogin" resultType="User">
        select * from t_user where username = #{param1} and password = #{param2}
    </select>

    <select id="checkLoginByMap" resultType="User">
        select * from t_user where username = #{username} and password = #{password}
    </select>

<!--    mapper接口方法的参数为实体类类型的参数-->
    <insert id="insertUser">
        insert into t_user values(null ,#{username},#{password},#{age},#{gender},#{email})
    </insert>

<!--    mapper接口方法的参数上设置@param注解-->
    <select id="checkLoginByParam" resultType="User">
        select * from t_user where username = #{username} and password = #{password}
    </select>
</mapper>

package com.qcw.mybatis.test;

import com.qcw.mybatis.mapper.UserMapper;
import com.qcw.mybatis.pojo.User;
import com.qcw.mybatis.utils.SqlSessionUtil;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.HashMap;
import java.util.Map;


public class ParameterTest {

    @Test
    public void getUserByUsernameTest(){
        SqlSession sqlSession = SqlSessionUtil.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);

        User user = mapper.getUserByUsername("wqc");
        System.out.println("user = " + user);
    }

    @Test
    public void checkLoginTest(){
        SqlSession sqlSession = SqlSessionUtil.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);

        User user = mapper.checkLogin("wqc", "12345");
        System.out.println("user = " + user);
    }

    @Test
    public void checkLoginByMapTest(){
        SqlSession sqlSession = SqlSessionUtil.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);

        Map<String,Object> map = new HashMap<>();
        map.put("username","wqc");
        map.put("password","12345");

        User user = mapper.checkLoginByMap(map);
        System.out.println("user = " + user);

    }

    @Test
    public void insertUserTest(){
        SqlSession sqlSession = SqlSessionUtil.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);

        User user = new User(null,"root","12357",26,"女","[e-mail]");
        mapper.insertUser(user);
        System.out.println("user = " + user);
    }

    @Test
    public void checkLoginByParamTest(){
        SqlSession sqlSession = SqlSessionUtil.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);

        User user = mapper.checkLoginByParam("wqc", "12345");
        System.out.println("user = " + user);
    }
}

注：代码为本人学习记录，仅供参考