mybatis XML 中if、choose、when、otherwise等标签的使用

一般使用在多条查询，虽然也可以通过注解写，我比较菜，我不会。

一般多条查询怎么解决？

1.如果是单表间的多条件查询我是直接调用mybatis plus的api ，里面可以有直接判空条件的api。

如:queryWrapper.like(StringUtils.isNotEmpty(变量参数), “表字段”,变量参数);

2.如果是多表间的多条件查询，我建议用XML来做吧，当然注解也行。

其实跟java的if类似，符合条件的就进去，那符合的进去，不符合的怎么办呢，

mybatis 提供了choose、when、otherwise这组标签组合着用，when就相当于if，otherwise就相当于else，但是when、otherwise需要放在choose里面才能使用。

这边我就用我最近遇到一个业务来演示吧。一个多表且不同表条件的查询 如下:

看看我的XML文件if、where、choose、when、otherwise等标签一条语句搞定。
建议模糊查询的参数在传参就先将参数做个处理，如: “%参数%”，网上也有人直接在XML里写成这样 ‘%’||’#{参数}||’%’，但是这种写法查出来的数据范围可能会偏大 。

小细节注意:COUNT(1) OVER() mysql 5.7 没有这个语法OVER() ==>分页查询返回总记录数

<?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="cn.mindgd.mapper.MaterielStorageMapper">
    <!--建立查询的列与对象属性的对应关系-->    <!--由于查出来的数据是多张表的，我这边就在实体类添加了一些渲染字段，下面用给这些字段取了别名-->
    <resultMap id="BaseResultMap" type="cn.mindgd.domain.MaterielStorage">
        <result column="materiel_storage_id" property="materielStorageId"/>
        <result column="material_code" property="materialCode"/>
        <result column="material_name" property="materialName"/>
        <result column="property_name" property="materialTypeName"/>
        <result column="stock" property="stock"/>
        <result column="total" property="total"/>
    </resultMap>

    <select id="findMaterielStorageByMore" resultMap="BaseResultMap">
        SELECT ms.materiel_storage_id AS materiel_storage_id,ms.position,m.material_code AS
        material_code,m.material_name AS
        material_name,dp.property_name AS property_name,ms.stock AS stock,COUNT(1) OVER() AS total
        FROM materiel_storage ms
        LEFT JOIN material m ON m.material_id=ms.material_id
        LEFT JOIN data_dictionary_property dp ON m.material_type_id=dp.property_id
        LEFT JOIN warehouse w ON w.warehouse_id=ms.warehouse_id
        LEFT JOIN construction_team ct ON ct.team_id =ms.team_id
        WHERE 1=1
        <choose>            <!-- 集合判空 --> 
            <when test="(null != warehouseIds and warehouseIds.size>0) and (null != teamIds and teamIds.size>0)"> 
                AND (
                w.warehouse_id IN
                <foreach collection="warehouseIds" item="warehouseId" open="(" separator=","
                         close=")">#{warehouseId}
                </foreach>
                OR ct.team_id
                IN
                <foreach collection="teamIds" item="teamId" open="(" separator=","
                         close=")">#{teamId}
                </foreach>
                )
            </when>
            <otherwise>
                <if test="null != warehouseIds and warehouseIds.size>0">
                    AND w.warehouse_id
                    IN
                    <foreach collection="warehouseIds" item="warehouseId" open="(" separator=","
                             close=")">#{warehouseId}
                    </foreach>
                </if>
                <if test="null != teamIds and teamIds.size>0">
                    AND ct.team_id
                    IN
                    <foreach collection="teamIds" item="teamId" open="(" separator=","
                             close=")">#{teamId}
                    </foreach>
                </if>
            </otherwise>
        </choose>
        <!-- 字符串判空 -->
        <if test="null != materialName and '' !=materialName">
            AND m.material_name like #{materialName}
        </if>

        <if test="null != materialCode and '' !=materialCode">
            AND m.material_code=#{materialCode}
        </if>
        <!-- Integer类型判空  如果加了 and '' !=propertyId ,0 就传不进去了，也就是不能像判断字符串一样去判断他是否是空字符串-->
        <if test="null != propertyId">
            AND dp.property_id=#{propertyId}
        </if>

        <if test="null != teamName and '' !=teamName">
            AND ct.team_name like #{teamName}
        </if>
        <if test="(null != currentPage) and (null != size)">
            LIMIT #{currentPage},#{size}
        </if>
    </select>
</mapper>

直接在测试类测试

@SpringBootTest
public class TestMaterielStorage {
    @Autowired(required = false)
    MaterielStorageMapper materielStorageMapper;


    @Test
    public void findMaterielStorageByMore() {
        List<Integer> warehouseIds = new ArrayList<>();
        warehouseIds.add(1);
        warehouseIds.add(2);
        List<Integer> teamIds = new ArrayList<>();
//        teamIds.add(1);
//        teamIds.add(2);
        List<MaterielStorage> materielStorageByMore =
//                materielStorageMapper.findMaterielStorageByMore("施", "P", null, 1, warehouseIds, teamIds, 0, 10);
                materielStorageMapper.findMaterielStorageByMore(null, null, null,
                        null, null, null, 0, 10);
        System.out.println("输出:" + materielStorageByMore);
    }
}

效果1：

效果2：

效果3：

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