动态SQL

    <select id="findUserList" parameterType="user" resultType="user">
        select * from user 
        where 1=1 
        <if test="id!=null and id!=‘‘">
        and id=#{id}
        </if>
        <if test="username!=null and username!=‘‘">
        and username like ‘%${username}%‘
        </if>
    </select>

<select id="findUserList" parameterType="user" resultType="user">
        select * from user 
        <where>
        <if test="id!=null and id!=‘‘">
        and id=#{id}
        </if>
        <if test="username!=null and username!=‘‘">
        and username like ‘%${username}%‘
        </if>
        </where>
    </select>

<if test="ids!=null and ids.size>0">
            <foreach collection="ids" open=" and id in(" close=")" item="id" separator="," >
                #{id}
            </foreach>
</if>

<select id="selectUserByList" parameterType="java.util.List" resultType="user">
        select * from user 
        <where>
        <!-- 传递List，List中是pojo -->
        <if test="list!=null">
        <foreach collection="list" item="item" open="and id in("separator=","close=")">
            #{item.id} 
        </foreach>
        </if>
        </where>
    </select>

    <select id="selectUserByArray" parameterType="Object[]" resultType="user">
        select * from user 
        <where>
        <!-- 传递数组 -->
        <if test="array!=null">
        <foreach collection="array" index="index" item="item" open="and id in("separator=","close=")">
            #{item.id} 
        </foreach>
        </if>
        </where>
    </select>

    <select id="selectUserByArray" parameterType="Object[]" resultType="user">
        select * from user 
        <where>
        <!-- 传递数组 -->
        <if test="array!=null">
        <foreach collection="array"index="index"item="item"open="and id in("separator=","close=")">
            #{item} 
        </foreach>
        </if>
        </where>
    </select>