Mybatis中的延迟加载案例解析

package cn.zhang.entity;
import java.util.HashSet;
import java.util.Set;
public class Dept {
 private Integer deptno;
 private String deptname;
 private Set emp = new HashSet();
 @Override
 public String toString() {
  return "Dept [deptno=" + deptno + ", deptname=" + deptname + ", emp="
    + emp + "]";
 }
 public Integer getDeptno() {
  return deptno;
 }
 public void setDeptno(Integer deptno) {
  this.deptno = deptno;
 }
 public String getDeptname() {
  return deptname;
 }
 public void setDeptname(String deptname) {
  this.deptname = deptname;
 }
 public Set getEmp() {
  return emp;
 }
 public void setEmp(Set emp) {
  this.emp = emp;
 }
}

package cn.zhang.entity;
public class Emp {
 private Integer empno;
 private String empname;
 @Override
 public String toString() {
  return "Emp [empno=" + empno + ", empname=" + empname + "]";
 }
 public Integer getEmpno() {
  return empno;
 }
 public void setEmpno(Integer empno) {
  this.empno = empno;
 }
 public String getEmpname() {
  return empname;
 }
 public void setEmpname(String empname) {
  this.empname = empname;
 }
}

package cn.zhang.util;
import java.io.IOException;
import java.io.Reader;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
/**
 * 工具类
 * 
 */
public class MybatisUtil {
 private static String cOnfig= "mybatis-config.xml";
 static Reader reader;
 static {
  try {
   reader = Resources.getResourceAsReader(config);
  } catch (IOException e) {
   e.printStackTrace();
  }
 }
 private static SqlSessionFactory factory = new SqlSessionFactoryBuilder()
   .build(reader);
 // 提供一个可以获取到session的方法
 public static SqlSession getSession() throws IOException {
  SqlSession session = factory.openSession();
  return session;
 }
}

package cn.zhang.dao;
import java.io.IOException;
import cn.zhang.entity.Dept;
public interface DeptDao {
 /**
  * 查询指定记录
  * @return
  * @throws IOException
  */
 public Dept findById(Integer id) throws IOException;
}

<&＃63;xml version="1.0" encoding="UTF-8" &＃63;>


 
 
  select empno,empname
  from emp where deptno=#{deptno}
 
 
 
  
  
  
  
  
  
 
 
 
  select deptno,deptname from dept
  where deptno=#{deptno}
 

<&＃63;xml version="1.0" encoding="UTF-8" &＃63;>


 
 
  
  
  
  
 
 
 
  
  
  
 
 
  
   
   
   
   
    
    
    
    
    
   
  
 
 
  
 

package cn.zhang.test;
//一对多
import java.io.IOException;
import org.apache.ibatis.session.SqlSession;
import org.junit.Before;
import org.junit.Test;
import cn.zhang.dao.DeptDao;
import cn.zhang.entity.Dept;
import cn.zhang.util.MybatisUtil;
public class MyTest {
 DeptDao dao;
 @Before
 public void initData() throws IOException{
  SqlSession session = MybatisUtil.getSession();
  dao = session.getMapper(DeptDao.class);
 }
 /**
  * 查询指定记录
  * @throws IOException
  */
 @Test
 public void findAll() throws IOException{
  Dept dept = dao.findById(1);
  System.out.println(dept);
 }
}