Mybatis collection 应用

遇到一个业务场景，我有两张表一张员工表(staff) 主键staff_id  另一张叫 (员工部门关系表)staff_department。
因为一个员工(staff)可以属于多个部门(department)，一个部门(department)会很多员工(staff)，所以staff_department是一个 staff_id 与 department_id的一张多对多的关系表。
现在我需要在mybatis 查询一条staff的时候获得当前这个staff关联的所有department，于是用到collection。

staff 实体类

package com.asclepius.slhdt.serv.dao.domain.staff;

/**
 * @author chensg
 *
 */

import java.io.Serializable;
import java.util.Date;
import java.util.List;

import org.springframework.format.annotation.DateTimeFormat;

import com.asclepius.slhdt.serv.dao.domain.department.Department;
import com.fasterxml.jackson.annotation.JsonFormat;

public class Staff implements Serializable {

	private static final long serialVersionUID = 1L;
	// 自动增长id
	private Integer staffIncId;
	// uuid
	private String staffId;
	// 姓名
	private String staffName;
	// 性别
	private Integer staffGender;
	
	// 所属部门
	private List<Department> departmentList;
	
	
	public Integer getStaffIncId() {
		return staffIncId;
	}
	public void setStaffIncId(Integer staffIncId) {
		this.staffIncId = staffIncId;
	}
	public String getStaffId() {
		return staffId;
	}
	public void setStaffId(String staffId) {
		this.staffId = staffId;
	}
	public String getStaffName() {
		return staffName;
	}
	public void setStaffName(String staffName) {
		this.staffName = staffName;
	}
	public Integer getStaffGender() {
		return staffGender;
	}
	public void setStaffGender(Integer staffGender) {
		this.staffGender = staffGender;
	}
	
	
	public List<Department> getDepartmentList() {
		return departmentList;
	}
	public void setDepartmentList(List<Department> departmentList) {
		this.departmentList = departmentList;
	}
	
	
}

staff与department是一个一对多关系，所以这里定义List<Department>

在xml中

<mapper namespace="com.asclepius.slhdt.serv.dao.mapper.staff.StaffMapper">

	<resultMap type="staff" id="staffResult">
		<id property="staffIncId" column="staff_inc_id" />
		<result property="staffId" column="staff_id" />
		<result property="staffName" column="staff_name" />
		<result property="staffGender" column="staff_gender" />
		<collection property="departmentList" column="staff_id" select="selectDepartment" ofType="department" javaType="ArrayList" />
	</resultMap>
	
	<select id="selectDepartment" parameterType="String" resultType="department" resultMap="departmentResult"  >  
        select SD.department_id, 
               D.department_parent_id,
               DP.department_name_alias 
               from shulan_staff_department SD
               left join shulan_department_prop DP on
               DP.department_id = SD.department_id
               left join shulan_department D on
               D.department_id = SD.department_id
               where SD.staff_id=#{staffId}  
    </select>  

	<resultMap type="department" id="departmentResult">
		<id property="departmentIncId" column="department_inc_id" />
		<result property="departmentId" column="department_id" />
		<result property="departmentParentId" column="department_parent_id" />
		<result property="departmentNameAlias" column="department_name_alias" />
	</resultMap>
<!-- 查询员工数据 -->
	<select id="getStaffById" parameterType="String" resultMap="staffResult">
		select S.staff_id,S.staff_name,S.staff_gender,
		from staff S
		where S.staff_id = #{param1}
	</select>

这里省去了很多staff中无关的字段。看collection标签 property="departmentList" 对应的就是实体类中的List<Department> departmentList属性。column与select要连在一起看，select=selectDepartment指的就是 下面id="selectDepartment的select映射SQL，column=staff_id指的就是关联主键的id。调用getstaffById就可以获得当前这个staff以及其关联的所有department