Day23——MyBatis自定义映射 collection

ゝ一纸荒年。 2023-07-04 14:09 16阅读 0赞

# 一. 知识储备 #

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwNjM0ODQ2_size_16_color_FFFFFF_t_70]

# 二. 例子 #

Department.java

package com.atguigu.mybatis.beans;
    
    import java.util.List;
    
    public class Department { 
    	
         private Integer id;
         private String departmentName;
         
         private List<Employee> emps;
         
         
    	public Department() { 
    		super();
    		// TODO Auto-generated constructor stub
    	}
    	
    	
    	public String getDepartmentName() { 
    		return departmentName;
    	}
    
    
    	public void setDepartmentName(String departmentName) { 
    		this.departmentName = departmentName;
    	}
    
    
    	public List<Employee> getEmps() { 
    		return emps;
    	}
    
    
    	public void setEmps(List<Employee> emps) { 
    		this.emps = emps;
    	}
    
    
    	public Integer getId() { 
    		return id;
    	}
    	public void setId(Integer id) { 
    		this.id = id;
    	}
    	public String getDepartment() { 
    		return departmentName;
    	}
    	public void setDepartment(String departmentName) { 
    		this.departmentName = departmentName;
    	}
    	@Override
    	public String toString() { 
    		return "Department [id=" + id + ", department=" + departmentName + "]";
    	}
         
    }

DepartmentMapperResultMap.java

package com.atguigu.mybatis.dao;
    
    import com.atguigu.mybatis.beans.Department;
    
    public interface DepartmentMapperResultMap { 
    
    	public Department selectDepartmentAndEmployees(Integer id);
    	
    }

DepartmentMapperResultMap.xml

<select id="selectDepartmentAndEmployees" resultMap="myDeptAndEmps">
    	     select d.id did, d.dept_name, e.id eid, e.last_name, e.email, e.gender
    	     from tbl_dept d left join tbl_employee e 
    	     on d.id = e.d_id where d.id = #{id}
    	</select>
    	<resultMap type="com.atguigu.mybatis.beans.Department" id="myDeptAndEmps">
    	     <id column="did" property="id"/>
    	     <result column="dept_name" property="departmentName"/>
    	     
    	      <collection property="emps" ofType="com.atguigu.mybatis.beans.Employee">
    	         <id column="eid" property="id"/>
    	         <result column="last_name" property="lastName"/>
    	         <result column="email" property="email"/>
    	         <result column="gender" property="gender"/>
    	      </collection>
    	</resultMap>

TestMyBatisResultMap.java

@Test
    	public void testResultMapCollection() throws Exception { 
    		SqlSessionFactory ssf = getSqlSessionFactory();
    		SqlSession session = ssf.openSession();
    		
    		try { 
                  DepartmentMapperResultMap mapper = 
                		  session.getMapper(DepartmentMapperResultMap.class);			
                  Department dept = mapper.selectDepartmentAndEmployees(1);
                  System.out.println(dept);
                  System.out.println(dept.getEmps());
    			
    			session.commit();
    		} finally { 
    			// TODO: handle finally clause
    			session.close();
    		}
    	}
    
    public SqlSessionFactory getSqlSessionFactory() throws Exception { 
    		String resource = "mybatis-config.xml"; 
    		InputStream inputStream = 
    				Resources.getResourceAsStream(resource); 
    		SqlSessionFactory sqlSessionFactory = 
    				new SqlSessionFactoryBuilder().build(inputStream);
    		return sqlSessionFactory;
    	}

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwNjM0ODQ2_size_16_color_FFFFFF_t_70]: https://img-blog.csdnimg.cn/20200211191719974.PNG?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwNjM0ODQ2,size_16,color_FFFFFF,t_70