14、MyBatis动态标签的使用详解

一、符号转义详解：

1、转义字符方式：

含义	原符号	转义字符
小于	<	&lt;
小于等于	<=	&lt;=
大于	>	&gt;
大于等于	>=	&gt;=
逻辑与（和）	&	&amp;
单引号	‘	&apos;
双引号	“	&quot;

# 查询创建时间是小于2023年的用户
SELECT * FROM user where create_at &lt '2023'

 

2、XML语法方式：

含义	原符号	转义字符
小于	<	<![CDATA[ < ]]>
小于等于	<=	<![CDATA[ <= ]]>
大于	>	<![CDATA[ > ]]>
大于等于	>=	<![CDATA[ >= ]]>
逻辑与（和）	&	<![CDATA[ & ]]>
单引号	‘	<![CDATA[ ’ ]]>
双引号	“	<![CDATA[ " ]]>

# 查询创建时间是小于2023年的用户
SELECT * FROM user where create_at <![CDATA[ < ]]> '2023'

 

二、动态＜if＞标签使用详解：

1、if标签判断不为空：

    <select id="selectAllDemo" resultMap="BaseResultMap" parameterType="java.lang.String">
        select
        <include refid="Base_Column_List"/>
        from page_demo
        where delete = 0
        <if test="id neq null and id != ''">
            AND uuid = #{id}
        </if>
    </select>

 

2、if标签判断String类型：

    <select id="selectAllDemo" resultMap="BaseResultMap" parameterType="java.lang.String">
        select
        <include refid="Base_Column_List"/>
        from page_demo
        where delete = 0
        <if test="name == 'one'.toString()">
            AND nums &gt; 10
        </if>
    </select>

 

3、if标签判断Integer类型：

MyBatis规定，MyBatis在进行判断时，会将Integer=0的参数默认为‘’（空串），允许数字与字符串做比较

方式一：

    <select id="selectAllDemo" resultMap="BaseResultMap" parameterType="java.lang.String">
        select
        <include refid="Base_Column_List"/>
        from page_demo
        where delete = 0
        <if test="nums != null">
            AND nums = #{nums }
        </if>
    </select>

方式二：

    <select id="selectAllDemo" resultMap="BaseResultMap" parameterType="java.lang.String">
        select
        <include refid="Base_Column_List"/>
        from page_demo
        where delete = 0
        <if test="nums > '0'.toString()">
            AND nums &gt; #{nums }
        </if>
    </select>

 

4、if标签判断Boolean类型：

方式一：

    <select id="selectAllDemo" resultMap="BaseResultMap" parameterType="java.lang.String">
        select
        <include refid="Base_Column_List"/>
        from page_demo
        where delete = 0
        <if test="isReport">
            AND is_report = 1
        </if>
    </select>

方式二：

    <select id="selectAllDemo" resultMap="BaseResultMap" parameterType="java.lang.String">
        select
        <include refid="Base_Column_List"/>
        from page_demo
        where delete = 0
        <if test="isReport != null and 'true'.toString() == isReport .toString()">
            AND is_report = #{isReport}
        </if>
    </select>

 

三、动态＜foreach＞标签使用详解：

1、foreach标签循环String类型：

  <select id="selectAllDemo" resultMap="BaseResultMap" parameterType="java.lang.String">
    select
    <include refid="Base_Column_List"/>
    from page_demo
    where delete = 0
    <if test="names != null and names != ''">
      AND (
      <foreach collection="names.split(',')" item="item" separator=" OR ">
        name LIKE CONCAT('%', #{item}, '%')
      </foreach>)
    </if>
    <if test="ids != null and ids != ''">
      AND  id IN
      <foreach collection="ids.split(',')" item="item" index="index" open="(" separator=","
               close=")">
        #{item}
      </foreach>
    </if>
  </select>

 

2、foreach标签循环List类型：

  <select id="selectAllDemo" resultMap="BaseResultMap" >
    select
    <include refid="Base_Column_List"/>
    from page_demo
    where delete = 0
    <if test="idList != null">
      id IN
      <foreach collection="idList" item="id" index="index" open="(" separator="," close=")">
        #{id, jdbcType=CHAR}
      </foreach>
    </if>
  </select>