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简介

MyBatis 是一款优秀的持久层框架，它支持自定义 SQL、存储过程以及高级映射。MyBatis 免除了几乎所有的 JDBC 代码以及设置参数和获取结果集的工作。MyBatis 可以通过简单的 XML 或注解来配置和映射原始类型、接口和 Java POJO（Plain Old Java Objects，普通老式 Java 对象）为数据库中的记录。

中文文档 https://mybatis.org/mybatis-3/zh/index.html

maven仓库

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<!-- https://mvnrepository.com/artifact/org.mybatis/mybatis -->
<dependency>
    <groupId>org.mybatis</groupId>
    <artifactId>mybatis</artifactId>
    <version>3.5.11</version>
</dependency>

环境搭建

安装MySQL

安装MySQL，这里不再赘述，网上很多相关资料

安装SQLyog

参考链接 https://www.jb51.net/article/263345.htm

密钥:

名称：any

证书秘钥：dd987f34-f358-4894-bd0f-21f3f04be9c1

创建数据库

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# 创建数据库
create database `mybatis`;
# 使用数据库
use `mybatis`;

创建表

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CREATE TABLE `user`(`id` INT(20) NOT NULL PRIMARY KEY,`name` VARCHAR(50) DEFAULT NULL,`pwd` VARCHAR(50) DEFAULT NULL)ENGINE=INNODB DEFAULT CHARSET=utf8;

插入数据

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INSERT INTO `user`(`id`,`name`,`pwd`) VALUES (1,'张三','123456');
INSERT INTO `user`(`id`,`name`,`pwd`) VALUES (2,'李四','123456');
INSERT INTO `user`(`id`,`name`,`pwd`) VALUES (3,'王五','123456');

引入MyBatis

1、打开IDEA,新建Maven项目

2、导入依赖

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<dependencies>
        <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.30</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/org.mybatis/mybatis -->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.11</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/junit/junit -->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.13.2</version>
            <scope>test</scope>
        </dependency>
    </dependencies>

为了方便测试，这里也导入了junit

3、创建一个模块

4、在新建的模块的resources目录下创建mybatis的配置文件

image-20230211172637897

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<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "https://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url"
                          value="jdbc:mysql://localhost:3306/mybatis?useSSL=true&amp;useUnicode=true&amp;characterEncoding=UTF-8"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>
        </environment>
    </environments>
    <!--这里的mapper可以先不配置，后面再配置-->
    <mappers>
        <mapper resource="com/wangyz/mapper/UserMapper.xml"/>
    </mappers>
</configuration>

5、编写MyBatisUtil工具类

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package com.wangyz.dao.util;

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.InputStream;

public class MyBatisUtil {

    private static SqlSessionFactory sqlSessionFactory;

    static {
        try {
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public static SqlSession getSqlSession() {
        return sqlSessionFactory.openSession();
    }

}

6、编写实体类

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package com.wangyz.pojo;

public class User {
    private int id;
    private String name;
    private String pwd;

    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 getPwd() {
        return pwd;
    }

    public void setPwd(String pwd) {
        this.pwd = pwd;
    }
    
    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", pwd='" + pwd + '\'' +
                '}';
    }
}

7、创建UserMapper

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package com.wangyz.mapper;

import com.wangyz.pojo.User;

import java.util.List;

public interface UserMapper {
    int insert(User user);
    int delete(User user);
    int update(User user);
    List<User> getUserList();
}

8、创建UserMapper.xml

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<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.wangyz.mapper.UserMapper">
    <select id="getUserList" resultType="com.wangyz.pojo.User">
        select * from User;
    </select>
</mapper>

9、在根目录的POM文件中配置build信息

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<build>
    <resources>
        <resource>
            <directory>src/main/resources</directory>
            <includes>
                <include>**/*.properties</include>
                <include>**/*.xml</include>
            </includes>
            <filtering>true</filtering>
        </resource>
        <resource>
            <directory>src/main/java</directory>
            <includes>
                <include>**/*.properties</include>
                <include>**/*.xml</include>
            </includes>
            <filtering>true</filtering>
        </resource>
    </resources>
</build>

10、测试

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import com.wangyz.mapper.UserMapper;
import com.wangyz.util.MyBatisUtil;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

public class UserMapperTest {
    @Test
    public void test() {
        SqlSession sqlSession = null;
        try {
            sqlSession = MyBatisUtil.getSqlSession();
            UserMapper mapper = sqlSession.getMapper(UserMapper.class);
            System.out.println(mapper.getUserList());
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (sqlSession != null) {
                sqlSession.close();
            }
        }
    }
}

输出结果：

[User{id=1, name=’张三’, pwd=’123456’}, User{id=2, name=’李四’, pwd=’123456’}, User{id=3, name=’王五’, pwd=’123456’}]

CRUD

1、根据id查询用户

  • Mapper

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    public interface UserMapper {
        User getUserById(int id);
    }

  • xml

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    <select id="getUserById" parameterType="int" resultType="com.wangyz.pojo.User">
        select * from user where id=#{id}
    </select>

  • 测试

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    @Test
    public void getUserById(){
        SqlSession sqlSession = null;
        try {
            sqlSession = MyBatisUtil.getSqlSession();
            UserMapper mapper = sqlSession.getMapper(UserMapper.class);
            System.out.println(mapper.getUserById(1));
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (sqlSession != null) {
                sqlSession.close();
            }
        }
    }

2、增加用户

  • Mapper

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    int insert(User user);

  • xml

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    <insert id="insert" parameterType="com.wangyz.pojo.User">
        insert into mybatis.user(id,name,pwd) values(#{id},#{name},#{pwd})
    </insert>

  • 测试

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    @Test
    public void insert(){
        SqlSession sqlSession = null;
        try {
            sqlSession = MyBatisUtil.getSqlSession();
            UserMapper mapper = sqlSession.getMapper(UserMapper.class);
            User user = new User(4,"haha","123456");
            int result = mapper.insert(user);
            if(result>0){
                //提交事务
                sqlSession.commit();
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (sqlSession != null) {
                sqlSession.close();
            }
        }
    }

3、修改用户

  • Mapper

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    int update(User user);

  • xml

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    <update id="update" parameterType="com.wangyz.pojo.User">
        update mybatis.user set name=#{name},pwd=#{pwd} where id = #{id}
    </update>

  • 测试

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    @Test
    public void update(){
        SqlSession sqlSession = null;
        try {
            sqlSession = MyBatisUtil.getSqlSession();
            UserMapper mapper = sqlSession.getMapper(UserMapper.class);
            User user = new User(4,"hi","000000");
            int result = mapper.update(user);
            if(result>0){
                //提交事务
                sqlSession.commit();
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (sqlSession != null) {
                sqlSession.close();
            }
        }
    }

4、删除用户

  • Mapper

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    int delete(int id);

  • xml

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    <delete id="delete" parameterType="int">
        delete from mybatis.user where id = #{id}
    </delete>

  • 测试

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    @Test
    public void delete(){
        SqlSession sqlSession = null;
        try {
            sqlSession = MyBatisUtil.getSqlSession();
            UserMapper mapper = sqlSession.getMapper(UserMapper.class);
            int result = mapper.delete(4);
            if(result>0){
                //提交事务
                sqlSession.commit();
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (sqlSession != null) {
                sqlSession.close();
            }
        }
    }

5、通过Map类型参数

  • Mapper

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    int insertByMap(Map<String,Object> map);

  • xml

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    <insert id="insertByMap" parameterType="map">
        insert into mybatis.user(id,name,pwd) values(#{userId},#{userName},#{userPwd})
    </insert>

  • 测试

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    @Test
    public void insertByMap(){
        SqlSession sqlSession = null;
        try {
            sqlSession = MyBatisUtil.getSqlSession();
            UserMapper mapper = sqlSession.getMapper(UserMapper.class);
            Map<String,Object> map = new HashMap<>();
            map.put("userId",4);
            map.put("userName","hello");
            map.put("userPwd","123456");
            int result = mapper.insertByMap(map);
            if(result>0){
                //提交事务
                sqlSession.commit();
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (sqlSession != null) {
                sqlSession.close();
            }
        }
    }

6、模糊查询

  • Mapper

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    List<User> getUserListByLike(String kw);

  • xml

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    <select id="getUserListByLike" resultType="com.wangyz.pojo.User">
        select * from mybatis.user where name like "%"#{value}"%"
    </select>

  • 测试

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    @Test
    public void getUserListByLike() {
        SqlSession sqlSession = null;
        try {
            sqlSession = MyBatisUtil.getSqlSession();
            UserMapper mapper = sqlSession.getMapper(UserMapper.class);
            System.out.println(mapper.getUserListByLike("王"));
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (sqlSession != null) {
                sqlSession.close();
            }
        }
    }

配置解析

环境配置

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<environments default="development">
    <environment id="development">
        ...
    </environment>
</environments>
<environments default="development">
    <environment id="test">
        ...
    </environment>
</environments>

可以通过default选项来设置环境

属性

1、编写配置文件 db.properties

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driver=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://localhost:3306/mybatis?useSSL=true&useUnicode=true&characterEncoding=UTF-8
username=root
password=root

2、引入配置

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<properties resource="db.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>

3、如果外部配置文件和mybatis.config存在同一字段，优先使用外部配置

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<properties resource="db.properties">
    <property name="username" value="root"/>
    <property name="password" value="123"/>
</properties>

上面的配置中，会优先使用db.properties中的username和password

类型别名

指定单个类的别名

1、在mybatis-config.xml中配置

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<typeAliases>
    <typeAlias type="com.wangyz.pojo.User" alias="User"/>
</typeAliases>

2、修改UserMapper.xml

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<select id="getUserList" resultType="User">
    select * from User;
</select>

使用包名

1、在mybatis-config.xml中配置

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<typeAliases>
    <package name="com.wangyz.pojo"/>
</typeAliases>

2、修改UserMapper.xml,默认别名为这个类的类名

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<select id="getUserList" resultType="User">
    select * from User;
</select>

使用建议

当类比较少时，可以用第一种，如果类较多，可以指定包名。也可以在类上加注解

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@Alias("user")
public class User {
}

Mapper

方式一【推荐】

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<!--每一个Mapper.xml都需要在MyBatis配置文件中注册-->
<mappers>
    <mapper resource="com/wangyz/mapper/UserMapper.xml"/>
</mappers>

方式二

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<!--每一个Mapper.xml都需要在MyBatis配置文件中注册-->
<mappers>
    <mapper class="com.wangyz.mapper.UserMapper"/>
</mappers>

接口和Mapper必须同名，而且需要在同一个包下

方式三

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<mappers>
   <package name="com.wangyz.mapper"/>
</mappers>

接口和Mapper必须同名，而且需要在同一个包下

ResultMap映射

1、修改字段pwd为password

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package com.wangyz.pojo;

public class User {
    private int id;
    private String name;
    private String password;

    public User() {
        
    }

    public User(int id, String name, String pwd) {
        this.id = id;
        this.name = name;
        this.password = pwd;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", pwd='" + password + '\'' +
                '}';
    }
}

2、修改mapper.xml

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<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.wangyz.mapper.UserMapper">

    <resultMap id="UserMap" type="User">
        <!--column:数据库中的一列,property:实体中的一个字段-->
        <result column="id" property="id"/>
        <result column="name" property="name"/>
        <result column="pwd" property="password"/>
    </resultMap>

    <select id="getUserList" resultMap="UserMap">
        select * from User;
    </select>
</mapper>

日志

标准日志

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<settings>
    <setting name="logImpl" value="STDOUT_LOGGING"/>
</settings>

image-20230217180104432

Log4J

1、引入Log4J

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<!-- https://mvnrepository.com/artifact/log4j/log4j -->
<dependency>
    <groupId>log4j</groupId>
    <artifactId>log4j</artifactId>
    <version>1.2.17</version>
</dependency>

2、在Resource目录下新建log4j.properties

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log4j.rootLogger=DEBUG,stdout
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%5p [%t] - %m%n

分页

Limit分页

1、接口

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List<User> getUserListByLimit(Map<String,Integer> map);

2、Mapper.xml

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<select id="getUserListByLimit" parameterType="map" resultMap="UserMap">
    select * from user limit #{startIndex},#{endIndex}
</select>

3、测试

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@Test
public void getUserListByLimit() {
    SqlSession sqlSession = null;
    try {
        sqlSession = MyBatisUtil.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        Map<String, Integer> map = new HashMap<>();
        map.put("startIndex", 0);
        map.put("endIndex", 2);
        System.out.println(mapper.getUserListByLimit(map));
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        if (sqlSession != null) {
            sqlSession.close();
        }
    }
}

分页插件

https://pagehelper.github.io/

@Insert("insert into user(id,name,pwd) values (#{id},#{name},#{pwd})")
int addUser(User user);

@Update("update user set name=#{name},pwd=#{pwd} where id=#{id}")
int updateUser(User user);

@Delete("delete from user where id=#{id}")
int deleteUser(@Param("id") int id);

}

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2、配置mapper

```xml
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "https://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <properties resource="db.properties"/>

    <settings>
        <setting name="logImpl" value="STDOUT_LOGGING"/>
    </settings>

    <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.wangyz.mapper.UserMapper"/>
    </mappers>
</configuration>

3、测试

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import com.wangyz.mapper.UserMapper;
import com.wangyz.pojo.User;
import com.wangyz.util.MyBatisUtil;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

public class UserMapperTest {
    @Test
    public void getUserList() {
        SqlSession sqlSession = null;
        try {
            sqlSession = MyBatisUtil.getSqlSession();
            UserMapper mapper = sqlSession.getMapper(UserMapper.class);
            System.out.println(mapper.getUserList());
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (sqlSession != null) {
                sqlSession.close();
            }
        }
    }

    @Test
    public void getUserListById() {
        SqlSession sqlSession = null;
        try {
            sqlSession = MyBatisUtil.getSqlSession();
            UserMapper mapper = sqlSession.getMapper(UserMapper.class);
            System.out.println(mapper.getUserById(1));
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (sqlSession != null) {
                sqlSession.close();
            }
        }
    }

    @Test
    public void addUser() {
        SqlSession sqlSession = null;
        try {
            sqlSession = MyBatisUtil.getSqlSession();
            UserMapper mapper = sqlSession.getMapper(UserMapper.class);
            mapper.addUser(new User(5,"hi","123456"));
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (sqlSession != null) {
                sqlSession.close();
            }
        }
    }

    @Test
    public void updateUser() {
        SqlSession sqlSession = null;
        try {
            sqlSession = MyBatisUtil.getSqlSession();
            UserMapper mapper = sqlSession.getMapper(UserMapper.class);
            mapper.updateUser(new User(5,"hey","12345678"));
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (sqlSession != null) {
                sqlSession.close();
            }
        }
    }

    @Test
    public void deleteUser() {
        SqlSession sqlSession = null;
        try {
            sqlSession = MyBatisUtil.getSqlSession();
            UserMapper mapper = sqlSession.getMapper(UserMapper.class);
            mapper.deleteUser(5);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (sqlSession != null) {
                sqlSession.close();
            }
        }
    }
}

Lombok

1、安装Lombok插件

在IDEA的插件中搜索Lombok,然后点击安装

2、引入依赖

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<!-- https://mvnrepository.com/artifact/org.projectlombok/lombok -->
<dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
    <version>1.18.24</version>
    <scope>provided</scope>
</dependency>

3、使用

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package com.wangyz.pojo;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

@Data
@AllArgsConstructor
@NoArgsConstructor
public class User {
    private int id;
    private String name;
    private String pwd;
}

查询嵌套

多对一

1、pojo

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package com.wangyz.mapper;

import com.wangyz.pojo.Student;

import java.util.List;

public interface StudentMapper {
    List<Student> getStudentList();
}


package com.wangyz.mapper;

import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Select;
import com.wangyz.pojo.Teacher;

public interface TeacherMapper {
    @Select("select * from teacher where id = #{id}")
    Teacher getTeacher(@Param("id") int id);
    
    List<Student> getStudentList2();
}

2、mapper

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


    <!--子查询，先查出所有学生，再查询老师的信息-->
    <select id="getStudentList" resultMap="StudentTeacher">
        select * from student
    </select>
    <resultMap id="StudentTeacher" type="Student">
        <result property="id" column="id"/>
        <result property="name" column="name"/>
        <association property="teacher" column="tid" javaType="Teacher" select="getTeacher"/>
    </resultMap>
    <select id="getTeacher" resultType="Teacher">
        select * from teacher where id=#{id}
    </select>

	<!--联表查询-->
    <select id="getStudentList2" resultMap="StudentTeacher2">
        select s.id sid,s.name sname,t.id tid,t.name tname from student as s,teacher as t where s.tid=t.id
    </select>
    <resultMap id="StudentTeacher2" type="Student">
        <result property="id" column="sid"/>
        <result property="name" column="sname"/>
        <association property="teacher" javaType="Teacher">
            <result property="id" column="tid"/>
            <result property="name" column="tname"/>
        </association>
    </resultMap>
</mapper>

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.wangyz.mapper.TeacherMapper">

</mapper>

一对多

1、pojo

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package com.wangyz.pojo;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

@Data
@AllArgsConstructor
@NoArgsConstructor
public class Student {
    private int id;
    private String name;
    private int tid;
}


package com.wangyz.pojo;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.util.List;

@Data
@AllArgsConstructor
@NoArgsConstructor
public class Teacher {
    private int id;
    private String name;

    private List<Student> students;
}

2、mapper

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<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.wangyz.mapper.TeacherMapper">
    <select id="getTeacherList" resultType="Teacher">
        select * from teacher
    </select>

    <select id="getTeacherList2" resultMap="TeacherStudent">
        select s.id sid,s.name sname,t.name tname,t.id tid
        from student s,teacher t
        where s.tid=t.id
    </select>
    <resultMap id="TeacherStudent" type="Teacher">
        <result property="id" column="tid"/>
        <result property="name" column="tname"/>
        <collection property="students" ofType="Student">
            <result property="id" column="sid"/>
            <result property="name" column="sname"/>
            <result property="tid" column="tid"/>
        </collection>
    </resultMap>
</mapper>

动态SQL

https://mybatis.org/mybatis-3/zh/dynamic-sql.html