xml 中的 > 和 <

符号 替换值
< &lt;
<= &lt;=
> &gt;
>= &gt;=
& &amp;

常见的表达式

if

<if test="id != null and id != ''">
    user_id = #{id}
</if>

if else 可用 choose…when…otherwise代替

<where>
    <choose>
        <when test="streetCode != null and streetCode != ''">
            bas.street_code = #{streetCode}
        </when>
        <otherwise>
            (bas.street_code like '%' or bas.street_code is NULL)
        </otherwise>
    </choose>

    <if test="statusCodeList != null and statusCodeList.size() > 0">
        and bas.status_code in
        <foreach collection="statusCodeList" item="item" index="index" open="(" close=")" separator=" , ">
            #{item}
        </foreach>
    </if>
    ...
</where>            

foreach

可直接指定分隔符,非常方便

<!-- List<String> statusCodes -->
...
 <if test="statusCodes != null and statusCodes.size() > 0">
    and bas.status_code in
    <foreach collection="statusCodes" item="item" index="index" open="(" close=")" separator=" , ">
        #{item}
    </foreach>
</if>
...