mybatis： 多对多查询[转]

Posted 2020-12-04 穆晟铭

加入3个包

log4j-1.2.17.jar

mybatis-3.3.0.jar

mysql-connector-java-5.1.8.jar

 

log4j需要配置

log4j.properties

# Global logging configuration
log4j.rootLogger=DEBUG, stdout
# Console output...
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%5p [%t] - %m%n

　　

 

目录如下

 

 

这里需要三个表 ：学生表、课程表和选课表

创建学生表 tb_student 并插入两条数据：

mysql> create table tb_student(
    -> s_id int primary key auto_increment,
    -> s_name varchar(20),
    -> s_sex varchar(10),
    -> s_age int);

insert into tb_student(s_name,s_sex,s_age) values(\'Tom\',\'male\',18);
insert into tb_student(s_name,s_sex,s_age) values(\'Jack\',\'male\',19);

　　

创建课程表 tb_course 并插入两条数据：

mysql> create table tb_course(
    -> c_id int primary key auto_increment,
    -> c_name varchar(20),
    -> c_credit int);

insert into tb_course(c_name,c_credit) values(\'Math\',5);
insert into tb_course(c_name,c_credit) values(\'Computer\',4);

　　

 

由于学生和课程是多对多的关联关系，因此创建中间表：选课表 tb_select_course 并插入数据

mysql> create table tb_select_course(
    -> sc_s_id int,
    -> sc_c_id int,
    -> sc_date date,
    -> primary key(sc_s_id,sc_c_id),
    -> foreign key(sc_s_id) references tb_student(s_id),
    -> foreign key(sc_c_id) references tb_course(c_id));

insert into tb_select_course(sc_s_id,sc_c_id,sc_date) values(1,1,\'2017-03-01\');
insert into tb_select_course(sc_s_id,sc_c_id,sc_date) values(1,2,\'2017-03-01\');
insert into tb_select_course(sc_s_id,sc_c_id,sc_date) values(2,1,\'2017-03-02\');
insert into tb_select_course(sc_s_id,sc_c_id,sc_date) values(2,2,\'2017-03-02\');

　　

 

我们的包名是： mybatis4

创建mybatis2.model，并创建相关的数据库model

student.java

package mybatis2.model;

import java.util.List;

public class Student {

	private int id;
	
	private String name;
	
	private String sex;
	
	private int age;	
	
	private List<Course> courses;
	
	
	
		
	
	
	

	public Student() {
		
	}

	public Student(int id, String name, String sex, int age, List<Course> courses) {		
		this.id = id;
		this.name = name;
		this.sex = sex;
		this.age = age;
		this.courses = courses;
	}

	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;
	}

	public String getSex() {
		return sex;
	}

	public void setSex(String sex) {
		this.sex = sex;
	}

	public int getAge() {
		return age;
	}

	public void setAge(int age) {
		this.age = age;
	}

	public List<Course> getCourses() {
		return courses;
	}

	public void setCourses(List<Course> courses) {
		this.courses = courses;
	}
	
	
	
	
	
}

　　

course.java

package mybatis2.model;

import java.util.List;

public class Course {

	private int id;
	
	private String name;
	
	private int credit;
	
	private List<Student> students;
	
	
	
	
	
	
	

	public Course() {
		
	}

	public Course(int id, String name, int credit, List<Student> students) {		
		this.id = id;
		this.name = name;
		this.credit = credit;
		this.students = students;
	}

	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;
	}

	public int getCredit() {
		return credit;
	}

	public void setCredit(int credit) {
		this.credit = credit;
	}

	public List<Student> getStudents() {
		return students;
	}

	public void setStudents(List<Student> students) {
		this.students = students;
	}
	
	
	
	
}

　　

StudentCourseLink.java

package mybatis2.model;

import java.util.Date;

public class StudentCourseLink {

	private Student student;
	
	private Course course;
	
	private Date date;
	
	
	
	

	public StudentCourseLink() {
	
	}

	public StudentCourseLink(Student student, Course course, Date date) {		
		this.student = student;
		this.course = course;
		this.date = date;
	}

	public Student getStudent() {
		return student;
	}

	public void setStudent(Student student) {
		this.student = student;
	}

	public Course getCourse() {
		return course;
	}

	public void setCourse(Course course) {
		this.course = course;
	}

	public Date getDate() {
		return date;
	}

	public void setDate(Date date) {
		this.date = date;
	}
	
	
	
	
}

　　

 

在mybatis2.mapper包下创建映射文件

StudentMapper.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org/DTD Mapper 3.0" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="mybatis2.mapper.StudentMapper">

<!-- 查询所有学生及他们的选课课程 -->
<select id="selectStudentCourse" resultMap="StudentCourseMap">
select s.*,c.* 
from 
tb_student s, tb_course  c, tb_select_course sc
where
s.s_id = sc.sc_s_id and c.c_id = sc.sc_c_id
</select>


<!-- 根据学生Id和选课Id,删除学生所选的课程 -->
<delete id="deleteStudentCourseById" parameterType="StudentCourseLink">
delete from tb_select_course where sc_s_id=#{student.s_id} and sc_c_id=#{course.c_id}
</delete>


<!-- resultMap映射实体类和数据库字段一一对应的关系 -->
<resultMap type="Student" id="StudentCourseMap">
	<id property="id" column="s_id" />
	<result property="name" column="s_name" />
	<result property="sex" column="s_sex"/>
	<result property="age" column="s_age"/>
	<!-- 多对多关系 -->
	<collection property="courses" ofType="Course">
		<id property="id" column="c_id"/>
		<result property="name" column="c_name"/>
		<result property="credit" column="c_credit"/>
	</collection>
</resultMap>


</mapper>

　　

StudentMapper.java

package mybatis2.mapper;

import java.util.List;

import mybatis2.model.Student;
import mybatis2.model.StudentCourseLink;



public interface StudentMapper {

	/**
	 * 鏌ヨ鎵?鏈夊鐢熷強浠栦滑鐨勮绋?
	 */
	public List<Student> selectStudentCourse() throws Exception;
	
	
	
	/**
	 * 鍒犻櫎鎸囧畾id鐢ㄦ埛鐨勬煇闂ㄨ绋嬶紙鍜屾牴鎹绋媔d锛夌殑閫夎鎯呭喌
	 */
	public void deleteStudentCourseById(StudentCourseLink scLink) throws Exception;
	
}

　　

在src目录下创建mybatis的配置文件

conf.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
	<!-- 引入数据库模型 -->
	<typeAliases>
			<!-- 引入单个模型
		<typeAlias  alias="Student" type="mybatis2.model.Student"/>
		<typeAlias  alias="Course" type="mybatis2.model.Course"/>
		<typeAlias  alias="StudentCourseLink" type="mybatis2.model.StudentCourseLink"/>
		--> 
		
		
		<!-- 指定一个类的包名起别名，将包内的java类的类名做为类的别名 -->
		<package name="mybatis2.model"/>
	</typeAliases>
	
	
	
	<!-- 配置mybatis运行环境 -->
	<environments default="development">
		<environment id="development">
			<!-- type=j"dbc" 代表用jdbcd的提交和回滚 -->
			<transactionManager type="JDBC"/>
			<!-- POOLED表示支持JDBC数据源连接池 -->
			<dataSource type="POOLED">
				<property name="driver" value="com.mysql.jdbc.Driver"/>
				<property name="url" value="jdbc:mysql://localhost:3306/spring"/>
				<property name="username" value="root"/>
				<property name="password" value=""/>
			</dataSource>
						
		</environment>
	</environments>
	

	
	<!-- 通过mapper映射接口包加载整个包的映射文件 -->
	<mappers>
		<!-- 单个映射文件引入--> 
		<mapper resource="mybatis2/mapper/StudentMapper.xml" />
		
		
		<!--package name="mybatis2/mapper"/-->
	</mappers>
</configuration>

　　

测试类

Test.java

package mybatis2.test;

import java.io.IOException;
import java.io.Reader;
import java.util.List;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import mybatis2.mapper.StudentMapper;
import mybatis2.model.Course;
import mybatis2.model.Student;



public class Test {

	private static SqlSessionFactory sqlSessionFactory;
	
	private static Reader reader;
	
	static {
		
		try {
			reader = Resources.getResourceAsReader("conf.xml");
			sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	
	private static SqlSessionFactory getSession()
	{
		return sqlSessionFactory;
	}
	
	
	public static void main(String[] args)
	{
		
		selectStudentCourse();
	}
	
	/**
	 * 鏌ヨ鎵?鏈夊鐢熷強鎵?閫夎绋?
	 */
	public static void selectStudentCourse()
	{
		SqlSession sqlSession = sqlSessionFactory.openSession();
		StudentMapper studentMapper = sqlSession.getMapper(StudentMapper.class);
		
		try {
			List<Student> students = studentMapper.selectStudentCourse();
			sqlSession.commit();
			for(Student stu: students)
			{
				System.out.println(stu.getId()+","+stu.getName()+","+stu.getSex()+","+stu.getAge());
				List<Course> courses = stu.getCourses();
				for(Course cour: courses)
				{
					System.out.println("__:" + cour.getId()+","+cour.getName()+","+cour.getCredit());
				}
			}
			
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
		//释放数据
		sqlSession.close();
	}
	
}