Mybatis collections应用获取包含多个List

你的名字 2022-07-15 05:16 148阅读 0赞

这是Mybatis的一个小例子，模糊查询  
***Dao层***

package com.dao;
    import java.util.List;
    import java.util.Map;
    import com.domain.Dept;
    public interface DeptMapper { 
        public List<Dept> getDeptList(Map<String, Object> param);
    }

***Mapper***

<?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="com.dao.SystemDeptMapper">
        <resultMap id="DeptMap" type="com.domain.Dept">
            <id column="id" property="deptId" />
            <result column="name" property="name" />
            <result column="parentId" property="parentId" />
            <result column="sortNo" property="sortNo" />
            <collection property="childList" ofType="com.domain.Dept"
                javaType="ArrayList" column="{parentId=id}" select="getDeptList" />
            <collection property="leaders" javaType="java.util.List"
                column="id" select="getLeaderList" />
        </resultMap>
        <select id="getDeptList" parameterType="map" resultMap="DeptMap">
            SELECT
            abd.id AS id,
            abd. NAME AS 'name',
            abd.parent_id AS parentId,
            abd.sort_no AS sortNo
            FROM
            abd
            WHERE
            parent_id =
            #{parentId}
            <if test="fuzzyName != null">
                AND
                abd. NAME like CONCAT('%','#{keyword}','%')
            </if>
        </select>
    
        <select id="getLeaderList" parameterType="java.lang.Integer" resultType="java.lang.String">
            SELECT DISTINCT
            au.`name`
            FROM
            au
            LEFT JOIN
            aa ON au.user_id = aa.user_id
            WHERE
            aa.dept_id = #{deptId}
        </select>
    
    </mapper>

***实体类***

package com.domain;
    
    import java.util.Date;
    import java.util.List;
    
    /** 1. @Description: 实体类 2. @Title Dept 3. @Package com.domain */
    public class Dept { 
    private Integer deptId;
    private String name;
    private Integer parentId;
    private Integer sortNo;
    private List<Dept> childList;
    private List<String> leaders;
    public Integer getDeptId() {
    return deptId;
    }
    public void setDeptId(Integer deptId) {
    this.deptId = deptId;
    }
    public String getName() {
    return name;
    }
    public void setName(String name) {
    this.name = name == null ? null : name.trim();
    }
    public Integer getParentId() {
    return parentId;
    }
    public void setParentId(Integer parentId) {
    this.parentId = parentId;
    }
    public Integer getSortNo() {
    return sortNo;
    }
    public void setSortNo(Integer sortNo) {
    this.sortNo = sortNo;
    }
    public List<Dept> getChildList() {
    return childList;
    }
    public void setChildList(List<Dept> childList) {
    this.childList = childList;
    }
    public List<String> getLeaders() {
    return leaders;
    }
    public void setLeaders(List<String> leaders) {
    this.leaders = leaders;
    }
    }

--------------------

小结：

1.  resultMap中可以添加多个collections标签，返回结果中可以套多个list
2.  若返回结果为一列，并且想让其转换为list，使resultType为resultType=”java.lang.String”
3.  模糊查询要使用concat，例如：`<if test="keyword != null"> AND name like CONCAT('%','#{keyword}','%') </if>`

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后语：  
初出茅庐，如有不足，请留言赐教。