mybatis的mapper对应的xml写法及配置详解

<?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.example.mapper.UserMapper">
    <!-- SQL 映射语句 -->
</mapper>

<!-- 简单查询 -->
<select id="getUserById" resultType="com.example.model.User">
	SELECT * FROM user WHERE id = #{id}
</select>

<insert id="insertUser" parameterType="com.example.model.User">
    INSERT INTO user (name, age) VALUES (#{name}, #{age})
</insert>

<update id="updateUser" parameterType="com.example.model.User">
    UPDATE user SET name = #{name}, age = #{age} WHERE id = #{id}
</update>

<delete id="deleteUserById" parameterType="int">
    DELETE FROM user WHERE id = #{id}
</delete>

<resultMap id="userResultMap" type="com.example.model.User">
    <id property="id" column="user_id"/>       <!-- 主键映射 -->
    <result property="name" column="user_name"/> <!-- 字段映射 -->
    <result property="age" column="user_age"/>
</resultMap>
<select id="getUserById" resultMap="userResultMap">
    SELECT user_id, user_name, user_age FROM user WHERE user_id = #{id}
</select>

<select id="searchUsers" resultType="com.example.model.User">
    SELECT * FROM user
    <where>
        <if test="name != null anconcatd name != ''">
            AND name LIKE CONCAT('%', #{name}, '%')
        </if>
        <if test="age != null">
            AND age = #{age}
        </if>
    </where>
</select>

<select id="findUser" resultType="com.example.model.User">
    SELECT * FROM user
    <where>
        <choose>
            <when test="type == 'name'">
                AND name = #{value}
            </when>
            <when test="type == 'email'">
                AND email = #{value}
            </when>
            <otherwise>
                AND status = 'active'
            </otherwise>
        </choose>
    </where>
</select>

<select id="getUsersByIds" resultType="com.example.model.User">
    SELECT * FROM user
    WHERE id IN
    <foreach item="id" collection="ids" open="(" separator="," close=")">
        #{id}
    </foreach>
</select>

<select id="getUsersByPage" resultType="com.example.model.User">
    SELECT * FROM user
    LIMIT #{offset}, #{limit}
</select>

@Select("SELECT * FROM user WHERE name = #{user_name} AND age = #{user_age}")
User getUserByNameAndAge(@Param("user_name") String userName, @Param("user_age") int userAge);

<select id="getUserById" resultType="com.example.model.User">
    SELECT user_id AS id, user_name AS name, user_age AS age FROM user
</select>