SSM框架下实现MyBatis连接查询，一对多和多对一

一、表

二、实体类

1、一个结果类（连接查询）

package com.cn.cust.entities;

//连接查询测试
public class StudentAndClassesName {

private String sName;
private String cName;
public String getsName() {
return sName;
}
public void setsName(String sName) {
this.sName = sName;
}
public String getcName() {
return cName;
}
public void setcName(String cName) {
this.cName = cName;
}
@Override
public String toString() {
return "StudentAndClassesName [sName=" + sName + ", cName=" + cName + "]";
}

}

2、Classes

package com.cn.cust.entities;

import java.util.List;

public class Classes {

private int id;
private String name;
private List<Student> studentList;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@Override
public String toString() {
return "Classes [id=" + id + ", name=" + name + "]";
}
public List<Student> getStudentList() {
return studentList;
}
public void setStudentList(List<Student> studentList) {
this.studentList = studentList;
}

}

3.Student

package com.cn.cust.entities;

public class Student {

private int id;
private String name;
private Classes classes;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@Override
public String toString() {
return "Student [id=" + id + ", name=" + name + "]";
}
public Classes getClasses() {
return classes;
}
public void setClasses(Classes classes) {
this.classes = classes;
}

}

三、持久层

1.comboDao

package com.cn.cust.dao;

import java.util.List;

import com.cn.cust.entities.StudentAndClassesName;

// 连接查询测试
public interface comboDao {

public List<StudentAndClassesName> findStudentAndClassesName();

}

2.ClassesDao

package com.cn.cust.dao;

import com.cn.cust.entities.Classes;

public interface ClassesDao {

public Classes getStudentsOfClass(int id);

}

3.StudentDao

package com.cn.cust.dao;

import com.cn.cust.entities.Student;

public interface StudentDao {

public StudentgetClassOfStudent(int id);

}

四、服务层

1、服务层接口

package com.cn.cust.service;

import java.util.List;

import com.cn.cust.entities.StudentAndClassesName;

public interface IStudentAndClassesService {
// 1、连接查询
public List<StudentAndClassesName> getStudentClasses();
// 2、一对多查询
public void selectClassesFetchStudent();
// 3、多对一查询
public void selectStudentFetchClasses();
}

2、服务层实现

package com.cn.cust.serviceImpl;

import java.util.List;

import javax.annotation.Resource;

import org.springframework.stereotype.Service;

import com.cn.cust.dao.ClassesDao;
import com.cn.cust.dao.StudentDao;
import com.cn.cust.dao.comboDao;
import com.cn.cust.entities.Classes;
import com.cn.cust.entities.Student;
import com.cn.cust.entities.StudentAndClassesName;
import com.cn.cust.service.IStudentAndClassesService;

@Service("studentAndClassesService")
public class StudentAndClassesServiceImpl implements IStudentAndClassesService {

@Resource
private comboDao my_combaDao;

@Resource
private ClassesDao classesDao;

@Resource
private StudentDao studentDao;

// 1、连接查询
@Override
public List<StudentAndClassesName> getStudentClasses() {
return this.my_combaDao.findStudentAndClassesName();
}

// 2、一对多查询
@Override
public void selectClassesFetchStudent() {
Classes classes = this.classesDao.getStudentsOfClass(11);
System.out.println(classes);
System.out.println(classes.getStudentList().size());
for(Student students : classes.getStudentList()) {
System.out.println(students);
}
}

// 3、多对一查询
@Override
public void selectStudentFetchClasses() {
Student student = this.studentDao.getClassOfStudent(1);
System.out.println(student);
System.out.println(student.getClasses());
}

}

五、测试类

package com.cn.cust.test;

import java.util.Iterator;
import java.util.List;

import javax.annotation.Resource;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;

import com.cn.cust.entities.StudentAndClassesName;
import com.cn.cust.service.IStudentAndClassesService;

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration("classpath:spring-mybatis.xml")
public class TestStudentClasses {

@Resource
private IStudentAndClassesService studentAndClassesService;

// 1、连接查询测试类
@Test
public void testLianJie() {
List<StudentAndClassesName> list = studentAndClassesService.getStudentClasses();
// 使用迭代器输出list中的内容
Iterator<StudentAndClassesName> it = list.iterator();
while (it.hasNext()) {
System.out.println(it.next());
}
System.out.println("成功！！");
}

// 2、一对多查询
@Test
public void testOneToMore() {
studentAndClassesService.selectClassesFetchStudent();
}

// 3、多对一查询
@Test
public void testMoreToOne() {
studentAndClassesService.selectStudentFetchClasses();
}

}

六、测试结果

1、连接查询

2、一对多，查询class(一)级联查询学生student(多)

3、多对一，查询student(多)级联查询class(一)

七、源码和数据库文件下载地址

http://download.csdn.net/detail/xiaoxiaoxiaohaozi/9406470