MyBatis之User.xml

<?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.njupt.pojo.User">

<select id="selectUserById" parameterType="string" resultType="com.njupt.pojo.User">
 select id ,name username , address  from user where id = #{id}
</select>

<select id="selectAllUsers" resultType="com.njupt.pojo.User">
 select id ,name , address  from user
</select>

<insert id="insertUser" parameterType="com.njupt.pojo.User">
 insert into user(id ,name , address) values(#{id},#{username},#{address})
</insert>

<select id="selectUserByIdForMap" parameterType="string" resultType="hashmap">
 select id ,name ,address from user where id = #{id}
</select>

<insert id="insertUserForMap" parameterType="hashmap">
  insert into user(id,name,address) values(#{id},#{username1},#{address});
</insert>

<delete id="deleteUserById" parameterType="string">
  delete from user where id = #{id}
</delete>

<update id="updateUserById" parameterType="com.njupt.pojo.User">
 update user set name = #{username} ,address = #{address} where id = #{id}
</update>

<update id="updateUserByIdForMap" parameterType="hashmap">
  update user set name = #{username2},address=#{address} where id = #{id}
</update>

<select id="selectUserByCondition" parameterType="com.njupt.pojo.User" resultType="com.njupt.pojo.User">
  select id , name username ,address from user where 1 = 1
  <if test="id != null">
     and id = #{id}
  </if>
  
  <if test="username != null">
     and name = #{username}
  </if>
  
  <if test="address != null">
     and address = #{address}
  </if>
</select>

<select id="selectUserByCondition1" parameterType="com.njupt.pojo.User" resultType="com.njupt.pojo.User">
 select id ,name as username ,address from user 
 <where>
    <if test="id != null">
        id = #{id}
    </if>
    
    <if test="username != null">
       and name = #{username}
    </if>
    
    <if test="address != null">
       and address = #{address}
    </if>
      
 </where>
</select>
</mapper>