映射关系(1-1 1-n n-n)

<resultMap id="userMap" type="User">
    <id property="id" column="id"></id>
    <result property="username" column="username"></result>
    <result property="password" column="password"></result>
    <result property="address" column="address"></result>
    <result property="email" column="email"></result>
    
    <collection property="roles" ofType="Role">
        <id property="id" column="role_id"></id>
        <result property="name" column="role_name"></result>
    </collection>
</resultMap>

{
    "id": "1003",
    "username": "小波",
    "password": "123456",
    "address": "北京市东城区",
    "email": "510273027@qq.com",
    "roles": [
        {
            "id": "1",
            "name": "开发"
        },
        {
            "id": "2",
            "name": "TL"
        }
    ]
}

<resultMap id="blogResult" type="Blog">
  <id property="id" column="blog_id" />
  <result property="title" column="blog_title"/>
  <association property="author" column="blog_author_id" javaType="Author" resultMap="authorResult"/>
</resultMap>
<resultMap id="authorResult" type="Author">
  <id property="id" column="author_id"/>
  <result property="username" column="author_username"/>
</resultMap>

<resultMap id="productBean" type="Blog">
  <id property="id" column="blog_id" />
  <result property="title" column="blog_title"/>
  <!-- 多对一 -->
  <!-- property: 指的是属性名称, javaType：指的是属性的类型 -->
  <association property="category" javaType="Author">
    <id column="cid" property="author_id"/>
    <result column="username" property="username"/>
  </association>
</resultMap>