1.前端传值后端接收各种类型的数据类型

1.list(@RequestParam Map<String, Object> params)

二.mapper层数据类型

1.map类型

注意：是按照表字段进行存储

string 值存入的是 表字段

Map<String,Object> getcateDao();

----》

 <select id="getcateDao" resultType="java.util.Map">
   SELECT *FROM `category` WHERE id= 1397844263642378242
    </select>

1.2map类型 带@MapKey("id")

k--->id || v-->object

@MapKey("id")
    Map<Long,Object> getcateDao();
------------------------------------
 <select id="getcateDao" resultType="java.util.Map">
   SELECT *FROM `category` WHERE id= 1397844263642378242
    </select>

1.3map类型 带@MapKey("id")

k--->id || v-->实体

@MapKey("id")
    Map<Long,Category> getcateDao();
------------------------------------------

 <select id="getcateDao" resultType="java.util.Map">
   SELECT *FROM `category` WHERE id= 1397844263642378242
    </select>

1.3实体和字段对应不上 一下做修改 添加resulMap

补充 添加resulMap

<resultMap id="resultmapC"  type="com.itheima.reggie.bean.Category">
  <id property="id" column="id"/>
  <result property="type" column="type"/>
  <result property="createTime" column="create_time"/>
  <result property="createUser" column="create_user"/>
  <result property="name" column="name"/>
  <result property="sort" column="sort"/>
  <result property="updateTime" column="update_time"/>
 </resultMap>

 <!--   <select id="categoryDaofind" resultType="java.lang.Integer">
         SELECT count(*) from category;
    </select>-->


 <select id="getcateDao" resultType="java.util.Map" resultMap="resultmapC">
   SELECT *FROM `category` WHERE id= 1397844263642378242
    </select>

2.List<Map<String, String>> querycateDao();

k--->字段 || v--->值

<select id="querycateDao" resultType="java.util.Map" >
   SELECT *FROM `category`
 </select>

2.2 @MapKey("id") List<Map<String, String>> querycateDao();

@MapKey("id")
    List<Map<String, String>> querycateDao();
---------------------------------------------------
 <select id="querycateDao" resultType="java.util.Map" >
   SELECT *FROM `category`
 </select>

2.3@MapKey("id") List<Map<String, Object>> querycateDao();

@MapKey("id")
    List<Map<String, Object>> querycateDao();
<!-- ======================================-->
 <select id="querycateDao" resultType="java.util.Map" >
   SELECT *FROM `category`

2.4.1@MapKey("id") List<Map<String, Category>> querycateDao();

自己写map类型数据 在引入进去 使用这种类型的

@MapKey("id")
    List<Map<String, Category>> querycateDao();
 
<!-- ======================================-->

 <resultMap id="resultmapCMap"  type="map">
  <id property="id" column="id"/>
  <result property="type" column="type"/>
  <result property="createTime" column="create_time"/>
  <result property="createUser" column="create_user"/>
  <result property="name" column="name"/>
  <result property="sort" column="sort"/>
  <result property="updateTime" column="update_time"/>
 </resultMap>

 <!-- ======================================-->
 <select id="querycateDao" resultMap="resultmapCMap"  >
   SELECT *FROM `category`
 </select>

2.4.2 List<Map<String, object>> querycateDao();

和2.4.1结果相同

可以遍历