创建mybatis-config.xml模板

 

 1

package com.kuang.dao;

import org.apache.ibatis.annotations.*;

import java.util.List;

public interface ClassDao {
    @Select("select * from c_class where id=#{id};")
    @Results({@Result(id = true,column = "id",property = "id"),
            @Result(column = "classname",property = "classname"),
            @Result(column="id",property = "studentList",javaType = List.class,
                    many = @Many(select = "com.kuang.dao.StudentDao.findStudentByCid"))})

    Class findClassStudentById(int id);

}
2

package com.kuang.dao;

import com.kuang.pojo.Student;
import org.apache.ibatis.annotations.*;

import java.util.List;

public interface StudentDao {
    @Select("select * from s_student where id=#{id};")
    Student findStudentById(int id);

    @Update({"update s_student set id=#{id},name=#{name},age=#{age},cid=#{cid} where id=#{id};"})
    int updateStudentById(Student student);
    @Select("select * from s_student where cid=#{cid};")
    List<Student> findStudentByCid(int cid);
}
3

package com.kuang.pojo;

import java.util.List;

public class Class {
    private int id;
    private String classname;
    private List<Student> studentList;

    public Class() {
    }

    public Class(int id, String classname, List<Student> studentList) {
        this.id = id;
        this.classname = classname;
        this.studentList = studentList;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getClassname() {
        return classname;
    }

    public void setClassname(String classname) {
        this.classname = classname;
    }

    public List<Student> getStudentList() {
        return studentList;
    }

    public void setStudentList(List<Student> studentList) {
        this.studentList = studentList;
    }

    @Override
    public String toString() {
        return "Class{" +
                "id=" + id +
                ", classname='" + classname + '\'' +
                ", studentList=" + studentList +
                '}';
    }
}

4

package com.kuang.pojo;

public class Student {
    private int id;
    private String name;
    private int age;
    private int cid;


    public Student() {
    }

    public Student(int id, String name, int age, int cid) {
        this.id = id;
        this.name = name;
        this.age = age;
        this.cid = cid;
    }

    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 getAge() {
        return age;
    }

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

    public int getCid() {
        return cid;
    }

    public void setCid(int cid) {
        this.cid = cid;
    }

    @Override
    public String toString() {
        return "Student{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", age=" + age +
                ", cid=" + cid +
                '}';
    }
}5

package com.kuang.utils;

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 java.io.IOException;
import java.io.Reader;

public class MybatisUtils {
    static SqlSessionFactory sqlSession=null;
    static {
        try {
            Reader reader = Resources.getResourceAsReader("mybatis-config.xml");
             sqlSession = new SqlSessionFactoryBuilder().build(reader);

        } catch (IOException e) {
            e.printStackTrace();
        }
    }

public static SqlSession getSqlSession(){
        return sqlSession.openSession();
    }
}
6
mybatis-config.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>
   <properties resource="jdbc.properties"/>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${driver}"/>
                <property name="url" value="${url}"/>
                <property name="username" value="${username}"/>
                <property name="password" value="${password}"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper class="com.kuang.dao.ClassDao"/>
        <mapper class="com.kuang.dao.StudentDao"/>
    </mappers>
</configuratio

7
text

import com.kuang.dao.StudentDao;
import com.kuang.pojo.Student;
import com.kuang.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

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

public class StudentDaoTest {
    SqlSession sqlSession= MybatisUtils.getSqlSession();
    StudentDao studentdao=sqlSession.getMapper(StudentDao.class);

    @Test
    public void findStudentByIdTest()
    {
        System.out.println("findStudentByIdTest:");
        Student student=studentdao.findStudentById(2);
        System.out.println(student);
        sqlSession.close();
    }

    @Test
    public void updateStudentByIdTest()
    {
        System.out.println("updateStudentByIdTest:");
        Student student=new Student();
        student.setId(2);
        student.setName("李雷");
        student.setAge(22);
        student.setCid(1);
        int result=studentdao.updateStudentById(student);
        sqlSession.commit();
        sqlSession.close();
        System.out.println("成功更新了"+result+"条数据");

    }


    @Test
    public void findStudentByCid()
    {
        System.out.println("findStudentByCid:");
        List<Student> student = studentdao.findStudentByCid(2);
        for (Student student1 : student) {
            System.out.println(student1.toString());

        }

    }
}
8
pom

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>org.example</groupId>
    <artifactId>diyiti</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
    </properties>
    <dependencies>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.28</version>
        </dependency>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.9</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>

        </dependency>
    </dependencies>

</project