<?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">

<!--核心根标签-->
<configuration>

    <!--引入数据库连接的配置文件-->
    <properties resource="jdbc.properties"/>

    <!--配置LOG4J-->
    <settings>
        <setting name="logImpl" value="log4j"/>
    </settings>

    <!--起别名-->
    <typeAliases>
        <package name="com.itheima.bean"/>
    </typeAliases>

    <!--  配置数据库环境， 环境可以有多个， defult属性是指哪一个  -->
    <environments default="mysql">
        <environment id="mysql">
            <!--transactionManager事务管理。-->
            <transactionManager type="JDBC"></transactionManager>
            <dataSource type="POOLED">
                <!--property获取数据库连接的配置信息-->
                <property name="driver" value="${driver}"/>
                <property name="url" value="${url}"/>
                <property name="username" value="${username}"/>
                <property name="password" value="${password}"/>
            </dataSource>
        </environment>
    </environments>

    <!--配置映射关系-->
    <mappers>
        <package name="com.itheima.mapper"/>
    </mappers>
    

</configuration>

2、创建接口和查询方法：

package com.itheima.mapper;

import com.itheima.bean.Student;
import org.apache.ibatis.annotations.Delete;
import org.apache.ibatis.annotations.Insert;
import org.apache.ibatis.annotations.Select;
import org.apache.ibatis.annotations.Update;

import java.util.List;

public interface StudentMapper {

    /**
     * 单表操作
     */
    //增
    @Insert("insert into student values (#{id}, #{name}, #{age})")
    public abstract Integer insert(Student student);

    //删
    @Delete("delete from student where id=#{id}")
    public abstract Integer delete(Integer id);

    //改
    @Update("update student set name=#{name}, age=#{age} where id=#{id};")
    public abstract Integer update(Student student);

    //查
    @Select("select * from student")
    public abstract List<Student> selsctAll();


    /**
     * 多表操作
     */
}

3、创建测试类：

package com.itheima.test;

import com.itheima.bean.Student;
import com.itheima.mapper.StudentMapper;
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 org.junit.Test;

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

public class Test01 {

    @Test
    public void selectAll() throws IOException {
        //1、加载核心配置文件
        InputStream is = Resources.getResourceAsStream("MyBatisConfig.xml");
        //2、获取SqlSession工厂对象
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);
        //3、获取到SqlSession对象
        SqlSession sqlSession = sqlSessionFactory.openSession(true);
        //4、获取StudentMapper接口实现对象
        StudentMapper mapper = sqlSession.getMapper(StudentMapper.class);
        //5、调用实现类对象中方法，接受结果
        List<Student> students = mapper.selsctAll();
        //6、处理结果
        for (Student student : students) {
            System.out.println(student);
        }
        //7、释放
        sqlSession.close();
        is.close();
    }


    @Test
    public void insert() throws IOException {
        //1、加载核心配置文件
        InputStream is = Resources.getResourceAsStream("MyBatisConfig.xml");
        //2、获取SqlSession工厂对象
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);
        //3、获取到SqlSession对象
        SqlSession sqlSession = sqlSessionFactory.openSession(true);
        //4、获取StudentMapper接口实现对象
        StudentMapper mapper = sqlSession.getMapper(StudentMapper.class);

        //5、调用实现类对象中方法，接受结果
        Student student = new Student(4, "赵六", 15);

        Integer result = mapper.insert(student);
        //6、处理结果
        System.out.println(result);
        //7、释放
        sqlSession.close();
        is.close();
    }


    @Test
    public void update() throws IOException {
        //1、加载核心配置文件
        InputStream is = Resources.getResourceAsStream("MyBatisConfig.xml");
        //2、获取SqlSession工厂对象
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);
        //3、获取到SqlSession对象
        SqlSession sqlSession = sqlSessionFactory.openSession(true);
        //4、获取StudentMapper接口实现对象
        StudentMapper mapper = sqlSession.getMapper(StudentMapper.class);

        //5、调用实现类对象中方法，接受结果
        Student student = new Student(4, "赵六", 99);

        Integer result = mapper.update(student);
        //6、处理结果
        System.out.println(result);
        //7、释放
        sqlSession.close();
        is.close();
    }

    @Test
    public void delete() throws IOException {
        //1、加载核心配置文件
        InputStream is = Resources.getResourceAsStream("MyBatisConfig.xml");
        //2、获取SqlSession工厂对象
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);
        //3、获取到SqlSession对象
        SqlSession sqlSession = sqlSessionFactory.openSession(true);
        //4、获取StudentMapper接口实现对象
        StudentMapper mapper = sqlSession.getMapper(StudentMapper.class);

        //5、调用实现类对象中方法，接受结果
        Integer id = 2;

        Integer result = mapper.delete(id);
        //6、处理结果
        System.out.println(result);
        //7、释放
        sqlSession.close();
        is.close();
    }

}

二、注解实现多表操作

一对一

1、相关属性标签介绍

2、实现步骤

①创建接口和查询方法

package com.itheima.one_to_one;

import com.itheima.bean.Card;
import com.itheima.bean.Person;
import org.apache.ibatis.annotations.One;
import org.apache.ibatis.annotations.Result;
import org.apache.ibatis.annotations.Results;
import org.apache.ibatis.annotations.Select;

import java.util.List;

public interface CardMapper {

    //查询全部
    @Select("select * from card")
    @Results({
            @Result(column = "id", property = "id"),
            @Result(column = "number", property = "number"),
            @Result(
                    property = "p",  //被包含对象的变量名
                    javaType = Person.class,  //被包含对象的实际数据类型
                    column = "pid", //代表根据查询出的card表中的pid字段来查询person表
                    /*
                    one、@One 一对一固定写法
                    select属性： 指调用哪个接口中的哪个方法
                     */
                    one = @One(select = "com.itheima.one_to_one.PersonMapper.selectById")
            )
    })
    public abstract List<Card> selectAll();
}

package com.itheima.one_to_one;

import com.itheima.bean.Person;
import org.apache.ibatis.annotations.Select;

public interface PersonMapper {

    @Select("select * from person where id=#{id}")
    public abstract Person selectById(Integer id);
}

?② 配置映射文件

<?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">

<!--核心根标签-->
<configuration>

    <!--引入数据库连接的配置文件-->
    <properties resource="jdbc.properties"/>

    <!--配置LOG4J-->
    <settings>
        <setting name="logImpl" value="log4j"/>


    </settings>

    <!--起别名-->
    <typeAliases>
        <!--用于指定要配置别名的包，当指定后，该报下的实体类都会注册别名，并且类名就是别名，不再区分大小写-->
        <package name="com.itheima.bean"/>
    </typeAliases>

    <!--集成分页助手插件-->
<!--    <plugins>-->
<!--        <plugin interceptor="com.github.pagehelper.PageInterceptor"/>-->
<!--    </plugins>-->


    <!--  配置数据库环境， 环境可以有多个， defult属性是指哪一个  -->
    <environments default="mysql">
        <environment id="mysql">
            <!--transactionManager事务管理。-->
            <transactionManager type="JDBC"></transactionManager>
            <dataSource type="POOLED">
                <!--property获取数据库连接的配置信息-->
                <property name="driver" value="${driver}"/>
                <property name="url" value="${url}"/>
                <property name="username" value="${username}"/>
                <property name="password" value="${password}"/>
            </dataSource>
        </environment>
    </environments>

    <!--配置映射关系-->
    <mappers>
        <package name="com.itheima.one_to_one"/>
    </mappers>

</configuration>

③ 编写测试类

package com.itheima.one_to_one;

import com.itheima.bean.Card;
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 org.junit.Test;

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

public class Test01 {

    @Test
    public void selectAll() throws IOException {
        InputStream is = Resources.getResourceAsStream("MyBatisConfig.xml");

        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);

        SqlSession sqlSession = sqlSessionFactory.openSession(true);

        CardMapper mapper = sqlSession.getMapper(CardMapper.class);  // 实现类对象


        List<Card> list = mapper.selectAll();

        for (Card card : list){
            System.out.println(card);
        }

        sqlSession.close();
        is.close();
    }
}

一对多

1、数据准备

班级-学生：一对多

要实现的查询：

1、实现步骤

①配置映射文件

②创建接口和查询方法

public interface ClassesMapper {
    
    @Select("select * from classes")
    @Results({
            @Result(column = "id", property = "id"),
            @Result(column = "name", property = "name"),
            @Result(
                    property = "students",
                    javaType = List.class,
                    column = "id",  // 根据查询出来的classes表的id字段来查询student表
                    /**
                     *  many = @Many：一对多查询的固定写法
                     *  select属性： 指调用哪个接口中的哪个查询方法
                    */
                    many = @Many(select = "com.itheima.one_to_many.StudentMapper.selectByCid")
            )
    })
    public abstract List<Classes> selectAll();
}

package com.itheima.one_to_many;

import com.itheima.bean.Student;
import org.apache.ibatis.annotations.Select;

import java.util.List;

public interface StudentMapper {

    @Select("select * from student where cid = #{cid}")
    public abstract List<Student> selectByCid(Integer cid);
}

③创建测试类

package com.itheima.one_to_many;

import com.itheima.bean.Card;
import com.itheima.bean.Classes;
import com.itheima.bean.Student;
import com.itheima.one_to_one.CardMapper;
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 org.junit.Test;

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

public class Test01 {

    @Test
    public void selectAll() throws IOException {
        InputStream is = Resources.getResourceAsStream("MyBatisConfig.xml");

        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);

        SqlSession sqlSession = sqlSessionFactory.openSession(true);

        ClassesMapper mapper = sqlSession.getMapper(ClassesMapper.class);  // 实现类对象


        List<Classes> list = mapper.selectAll();

        for (Classes classes : list) {
            System.out.println(classes.getId() +" "+ classes.getName());
            List<Student> students = classes.getStudents();
            for (Student student : students) {
                System.out.println(student);
            }
        }

        sqlSession.close();
        is.close();
    }
}

多对多

1、数据准备

?2、实现步骤

①配置映射文件

②创建接口和查询方法

注意：这里是多对多可能会出现以下情况：比如我们要查询每一个学生的信息，包括他所有选的课程。有的学生没有选课也会被查询出来。这时候要借助中间表，将没有选课的学生过滤掉。

package com.itheima.many_to_many;

import com.itheima.bean.Student;
import org.apache.ibatis.annotations.Many;
import org.apache.ibatis.annotations.Result;
import org.apache.ibatis.annotations.Results;
import org.apache.ibatis.annotations.Select;

import java.util.List;

public interface StudentMapper {

    // 查询全部
    @Select("select distinct s.id, s.name, s.age from student s, stu_cr sc where sc.sid = s.id")
    @Results({
            @Result(column = "id", property = "id"),
            @Result(column = "name", property = "name"),
            @Result(column = "age", property = "age"),
            @Result(
                  property = "courses",  //被包含对象的变量名
                  javaType = List.class,  //被包含对象的实际数据类型
                  column = "id",  //根绝查询出student表的id作为关联条件，去查询中间表和课程表

                  many = @Many(select = "com.itheima.many_to_many.CourseMapper.selectBySid")
            )
    })
    public abstract List<Student> selectAll();


}

package com.itheima.many_to_many;

import com.itheima.bean.Course;
import org.apache.ibatis.annotations.Select;

import java.util.List;

public interface CourseMapper {

    @Select("select c.id,c.name from stu_cr sc, course c where sc.cid=c.id and sc.sid = #{id}")
    public abstract List<Course> selectBySid(Integer id);
}

③编写测试类

package com.itheima.many_to_many;

import com.itheima.bean.Classes;
import com.itheima.bean.Course;
import com.itheima.bean.Student;
import com.itheima.one_to_many.ClassesMapper;
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 org.junit.Test;

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

public class Test01 {
    @Test
    public void selectAll() throws IOException {
        InputStream is = Resources.getResourceAsStream("MyBatisConfig.xml");

        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);

        SqlSession sqlSession = sqlSessionFactory.openSession(true);

        StudentMapper mapper = sqlSession.getMapper(StudentMapper.class);  // 实现类对象


        List<Student> list = mapper.selectAll();

        for (Student student : list) {
            System.out.println(student.getId() +" "+ student.getName() +" "+ student.getAge());
            List<Course> courses = student.getCourses();
            for (Course course : courses) {
                System.out.println(course);
            }
        }

        sqlSession.close();
        is.close();
    }
}