MyBatis的collection集合的分布查询

 MyBatis的collection集合的分布查询

DepartmentMapper.java

package com.cn.mybatis.dao;

import java.util.List;
import java.util.Map;


import org.apache.ibatis.annotations.MapKey;
import org.apache.ibatis.annotations.Param;

import com.cn.zhu.bean.Department;
import com.cn.zhu.bean.Employee;

public interface DepartmentMapper {
	public Department getDeptById(Integer id);
	public Department getDeptByIdPlus(Integer id);
	
	public Department getDeptByIdStep(Integer id);
	public List<Employee> getEmpsByDeptId(Integer deptId);
 }
   

EmployeeMapperPlus.java

[java] view plain copy

1. package com.cn.mybatis.dao;  
2.   
3. import java.util.List;  
4. import java.util.Map;  
5.   
6.   
7. import org.apache.ibatis.annotations.MapKey;  
8. import org.apache.ibatis.annotations.Param;  
9.   
10. import com.cn.zhu.bean.Employee;  
11.   
12. public interface EmployeeMapperPlus {  
13.     public Employee getEmpById(Integer id);  
14.     public Employee getEmpAndDept(Integer id);  
15.     public Employee getEmpByIdStep(Integer id);  
16.  }  

Department.java

[java] view plain copy

1. package com.cn.zhu.bean;  
2.   
3. import java.util.List;  
4.   
5. public class Department {  
6.     private     Integer  id;  
7.     private  String  departmentName;  
8.     private List<Employee> emps;  
9.       
10.       
11.       
12.     public List<Employee> getEmps() {  
13.         return emps;  
14.     }  
15.     public void setEmps(List<Employee> emps) {  
16.         this.emps = emps;  
17.     }  
18.     public Integer getId() {  
19.         return id;  
20.     }  
21.     public void setId(Integer id) {  
22.         this.id = id;  
23.     }  
24.     public String getDepartmentName() {  
25.         return departmentName;  
26.     }  
27.     public void setDepartmentName(String departmentName) {  
28.         this.departmentName = departmentName;  
29.     }  
30.     @Override  
31.     public String toString() {  
32.         return "Department [departmentName=" + departmentName + ", id=" + id  
33.                 + "]";  
34.     }  
35.       
36. }  

DepartmentMapper.xml

<?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.cn.mybatis.dao.DepartmentMapper">
	<!-- public Department getDeptById(Integer id); -->
	<select id="getDeptById" resultType="com.cn.zhu.bean.Department">
		select id,dept_name
		departmentName from tbl_dept where id=#{id}
    </select>
    
    
	
	<!-- collection集合分段查询 -->
	<resultMap type="com.cn.zhu.bean.Department" id="MyDeptStept">
		<id column="id" property="id" />
		<result column="dept_name" property="departmentName" />
		<collection property="emps"
			select="com.cn.mybatis.dao.EmployeeMapperPlus.getEmpsByDeptId"
			column="{deptId=id}">
		</collection>
	</resultMap>
	<!-- public Department getDeptByIdStep(Integer id); -->
	<select id="getDeptByIdStep" resultMap="MyDeptStept">
		select id,dept_name departmentName from tbl_dept where id=#{id}
    </select>
	<!--  扩展,多列的值传递过去 
              将多列的值封装map传递
              column="{key1=column,key2=column2}"
              fetchType="lazy" : 表示使用延迟加载
                  lazy 延迟
                  eager 立即加载
    -->

</mapper>

EmployeeMapperPlus.xml

<?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.cn.mybatis.dao.EmployeeMapperPlus">

	
 	<!-- 分布好处  可以使用延迟加载
 	     Employee==>Dept
 	          我们每次查询Employee对象的时候，都将一起查询出来。
 	          部门信息在我们使用的时候再去查询
 	          分段查询的基础之上加上两个配置
 	 -->
 	 
 	 <!-- 
 	       查询二
 	      查询部门的时候将部门对应的所有员工信息也查询出来
 	    	public List<Employee> getEmpsByDeptId(Integer deptId);
 	  -->
 	  <select resultType="com.cn.zhu.bean.Employee" id="getEmpsByDeptId">
 	     select * from tbl_employee where d_id=#{deptId}
 	  </select>
</mapper>

mybatis-config.xml

[html] view plain copy

1. <mappers>  
2.     <mapper resource="mybatis/mapper/EmployeeMapperPlus.xml" />  
3.     <mapper resource="mybatis/mapper/DepartmentMapper.xml" />  
4. </mappers>