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MyBaits的注解开发

阿瞒有我良计15 2023-07-10 08:00:03
简介MyBaits的注解开发

为什么要用MyBaits注解开发？

前面介绍了MyBatis的基本用法、关联映射、动态SQL和缓存机制等知识，所有的配置都是基于XML文件完成的，但在实际开发中，大量的XML配置文件的编写是非常繁琐的，为此，MyBatis提供了更加简便的基于注解的配置方式。

基于注解的单表增删改查 

代码示例：

1.pom.xml引入项目需要的依赖

<?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>_20230503</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>5.2.3.RELEASE</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-beans</artifactId>
            <version>5.2.3.RELEASE</version>
        </dependency>

        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.2</version>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.11</version>
        </dependency>

        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>
    </dependencies>

</project>

2.建表∶在mybatis数据库中创建名为tb_worker的数据表，同时预先插入几条测试数据。

3.根据数据库的表结构，创建实体类Worker

package cn.hdc.pojo;

public class Worker {
    private int id;
    private String name;
    private int age;
    private String sex;
    private String worker_id;

    @Override
    public String toString() {
        return "Worker{" +
                "id=" + id +
                ", name='" + name + ''' +
                ", age=" + age +
                ", sex='" + sex + ''' +
                ", worker_id='" + worker_id + ''' +
                '}';
    }

    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 String getSex() {
        return sex;
    }

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

    public String getWorker_id() {
        return worker_id;
    }

    public void setWorker_id(String worker_id) {
        this.worker_id = worker_id;
    }
}

 4.创建WorkerMapper接口声明要实现的方法：

package cn.hdc.mapper;

import cn.hdc.pojo.Worker;
import org.apache.ibatis.annotations.*;

public interface WorkerMapper {
    @Select("select * from tb_worker where id=#{id}")
    public Worker findWorker(int id);

    @Insert("insert into tb_worker values (null,#{name},#{age},#{sex},#{worker_id})")
    public int insertWorker(Worker worker);

    @Update("update tb_worker set name=#{name},age=#{age} where id=#{id}")
    public int updateWorker(Worker worker);

    @Delete("delete from tb_worker where id=#{id}")
    public int deleteWorker(int id);


    @Select("select * from tb_worker where id=#{param1} and name=#{param2}")
    public Worker selectWorkerByIdAndName(@Param("param1") int id, @Param("param2") String name);

}

5.创建MyBatisUtils工具类

package cn.hdc.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 {
    private static SqlSessionFactory sqlSessionFactory = null;
 
    static {
        try {
            Reader reader = Resources.getResourceAsReader("mybatis-config.xml");
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }
 
    public static SqlSession getSession() {
        return sqlSessionFactory.openSession();
    }
}

6.创建db.properties

driver.driver=com.mysql.cj.jdbc.Driver
driver.url=jdbc:mysql://localhost:3306/mybatis?serverTimezone=UTC&characterEncoding=utf8&useUnicode=true&useSSL=false
driver.username=root
driver.password=666666

7.创建mybaits-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>
    <!-- 环境配置 -->
    <!-- 加载类路径下的属性文件 -->
    <properties resource="db.properties"/>

    <!-- 数据库连接相关配置 ,db.properties文件中的内容-->
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${driver.driver}"/>
                <property name="url" value="${driver.url}"/>
                <property name="username" value="${driver.username}"/>
                <property name="password" value="${driver.password}"/>
            </dataSource>
        </environment>
    </environments>
    
    <mappers>
        <package name="cn.hdc.mapper"/>
    </mappers>
</configuration>

8.创建测试类WorkerMapperTest

package cn.hdc.mapper;

import cn.hdc.pojo.Worker;
import cn.hdc.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

public class WorkerMapperTest {
    private WorkerMapper workerMapper;
    private SqlSession session;

    @Before
    public void setUp() throws Exception {
        session = MybatisUtils.getSession();
    }

    @After
    public void tearDown() throws Exception {
        session.commit();
        session.close();
    }

    @Test
    public void findWorker() {
        workerMapper = session.getMapper(WorkerMapper.class);
        Worker worker = workerMapper.findWorker(1);
        System.out.println(worker);
    }

    @Test
    public void insertWorker() {
        workerMapper = session.getMapper(WorkerMapper.class);
        Worker worker = new Worker();
        worker.setName("赵六");
        worker.setAge(23);
        worker.setSex("男");
        worker.setWorker_id("1004");
        int i = workerMapper.insertWorker(worker);
        if (i > 0) {
            System.out.println("插入成功!");
        } else {
            System.out.println("插入失败！");
        }
    }

    @Test
    public void updateWorker() {
        workerMapper = session.getMapper(WorkerMapper.class);
        Worker worker = new Worker();
        worker.setName("李华");
        worker.setAge(30);
        worker.setId(4);
        int ret = workerMapper.updateWorker(worker);
        if (ret > 0) {
            System.out.println("修改成功!");
        } else {
            System.out.println("修改失败！");
        }
    }

    @Test
    public void deleteWorker() {
        workerMapper = session.getMapper(WorkerMapper.class);
        int ret = workerMapper.deleteWorker(4);
        if (ret > 0) {
            System.out.println("删除成功!");
        } else {
            System.out.println("删除失败！");
        }
    }

    @Test
    public void selectWorkerByIdAndName() {
        workerMapper = session.getMapper(WorkerMapper.class);
        Worker worker = workerMapper.selectWorkerByIdAndName(3, "王五");
        System.out.println(worker);
    }
}

9.项目结构：

10.@Param注解说明：

在MyBatis中，@param注解用于为SQL语句中的参数提供名称和值。它将参数名称和值映射到SQL语句中的占位符（？）或具名参数上。当使用动态SQL时，@param注解还可以帮助 MyBatis 明确哪些参数是必须提供的，哪些是可选的。使用@param注解可以提高代码可读性和维护性，并且可以避免潜在的bug。 

基于注解的关联查询

—对一查询:

代码示例：

1.pom.xml

<?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>_20230503</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>5.2.3.RELEASE</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-beans</artifactId>
            <version>5.2.3.RELEASE</version>
        </dependency>

        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.2</version>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.11</version>
        </dependency>

        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>
    </dependencies>

</project>

2.建库，建表：

tb_person表：

CREATE TABLE `tb_person` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(32) DEFAULT NULL,
  `age` int(11) DEFAULT NULL,
  `sex` varchar(8) DEFAULT NULL,
  `card_id` int(11) DEFAULT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `card_id` (`card_id`),
  CONSTRAINT `tb_person_ibfk_1` FOREIGN KEY (`card_id`) REFERENCES `tb_idcard` (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8mb4

tb_idcard表：

CREATE TABLE `tb_idcard` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `code` varchar(18) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8mb4

3.创建实体类：Person

package cn.hdc.pojo;

public class Person {
    private int id;
    private String name;
    private int age;
    private String sex;
    private IdCard idCard;

    @Override
    public String toString() {
        return "Person{" +
                "id=" + id +
                ", name='" + name + ''' +
                ", age=" + age +
                ", sex='" + sex + ''' +
                ", idCard=" + idCard +
                '}';
    }

    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 String getSex() {
        return sex;
    }

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

    public IdCard getIdCard() {
        return idCard;
    }

    public void setIdCard(IdCard idCard) {
        this.idCard = idCard;
    }
}

4.创建实体类：IdCard:

package cn.hdc.pojo;

public class IdCard {
    private int id;
    private String code;

    @Override
    public String toString() {
        return "IdCard{" +
                "id=" + id +
                ", code='" + code + ''' +
                '}';
    }

    public int getId() {
        return id;
    }

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

    public String getCode() {
        return code;
    }

    public void setCode(String code) {
        this.code = code;
    }
}

5.创建接口IdCardMapper:

package cn.hdc.mapper;

import cn.hdc.pojo.IdCard;
import org.apache.ibatis.annotations.Select;

public interface IdCardMapper {
    @Select("select * from tb_idCard where id = #{id}")
    public IdCard selectIdCardById(int id);
}

6.创建接口PersonMapper:

package cn.hdc.mapper;

import cn.hdc.pojo.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;

public interface PersonMapper {
    @Select("select * from tb_person where id=#{id}")
    @Results(@Result(
            column = "card_id",
            property = "idCard",
            one = @One(select = "cn.hdc.mapper.IdCardMapper.selectIdCardById")
    ))
    public Person selectPersonById(int id);
}

7.创建MyBatisUtils工具类：

package cn.hdc.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 {
    private static SqlSessionFactory sqlSessionFactory = null;
 
    static {
        try {
            Reader reader = Resources.getResourceAsReader("mybatis-config.xml");
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }
 
    public static SqlSession getSession() {
        return sqlSessionFactory.openSession();
    }
}

8.db.properties:

driver.driver=com.mysql.cj.jdbc.Driver
driver.url=jdbc:mysql://localhost:3306/mybatis?serverTimezone=UTC&characterEncoding=utf8&useUnicode=true&useSSL=false
driver.username=root
driver.password=666666

9.mybaits-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>
    <!-- 环境配置 -->
    <!-- 加载类路径下的属性文件 -->
    <properties resource="db.properties"/>

    <!-- 数据库连接相关配置 ,db.properties文件中的内容-->
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${driver.driver}"/>
                <property name="url" value="${driver.url}"/>
                <property name="username" value="${driver.username}"/>
                <property name="password" value="${driver.password}"/>
            </dataSource>
        </environment>
    </environments>
    
    <mappers>
        <package name="cn.hdc.mapper"/>
    </mappers>
</configuration>

10.创建PersonMapperTest,测试类：

package cn.hdc.mapper;

import cn.hdc.pojo.Person;
import cn.hdc.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import static org.junit.Assert.*;

public class PersonMapperTest {
    private SqlSession session;
    private PersonMapper personMapper;

    @Before
    public void setUp() throws Exception {
        session = MybatisUtils.getSession();
    }

    @After
    public void tearDown() throws Exception {
        session.commit();
        session.close();
    }

    @Test
    public void selectPersonById() {
        personMapper = session.getMapper(PersonMapper.class);
        Person person = personMapper.selectPersonById(1);
        System.out.println(person);
    }
}

11.项目结构：

12.运行结果：

一对多查询：

代码示例：

1.pom.xml

<?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>_20230503</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>5.2.3.RELEASE</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-beans</artifactId>
            <version>5.2.3.RELEASE</version>
        </dependency>

        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.2</version>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.11</version>
        </dependency>

        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>
    </dependencies>

</project>

2.db.properties

driver.driver=com.mysql.cj.jdbc.Driver
driver.url=jdbc:mysql://localhost:3306/mybatis?serverTimezone=UTC&characterEncoding=utf8&useUnicode=true&useSSL=false
driver.username=root
driver.password=666666

3.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>
    <!-- 环境配置 -->
    <!-- 加载类路径下的属性文件 -->
    <properties resource="db.properties"/>

    <!-- 数据库连接相关配置 ,db.properties文件中的内容-->
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${driver.driver}"/>
                <property name="url" value="${driver.url}"/>
                <property name="username" value="${driver.username}"/>
                <property name="password" value="${driver.password}"/>
            </dataSource>
        </environment>
    </environments>
    
    <mappers>
        <package name="cn.hdc.mapper"/>
    </mappers>
</configuration>

4.MyBaitsUtils工具类：

package cn.hdc.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 {
    private static SqlSessionFactory sqlSessionFactory = null;
 
    static {
        try {
            Reader reader = Resources.getResourceAsReader("mybatis-config.xml");
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }
 
    public static SqlSession getSession() {
        return sqlSessionFactory.openSession();
    }
}

5.建库建表：

tb_user表：

CREATE TABLE `tb_user` (
  `id` int(32) NOT NULL AUTO_INCREMENT,
  `username` varchar(32) DEFAULT NULL,
  `address` varchar(256) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8mb4

tb_orders表：

CREATE TABLE `tb_orders` (
  `id` int(32) NOT NULL AUTO_INCREMENT,
  `number` varchar(32) NOT NULL,
  `user_id` int(32) NOT NULL,
  PRIMARY KEY (`id`),
  KEY `user_id` (`user_id`),
  CONSTRAINT `tb_orders_ibfk_1` FOREIGN KEY (`user_id`) REFERENCES `tb_user` (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8mb4

6.创建实体类：User:

package cn.hdc.pojo;

import java.util.List;

public class User {
    private int id;
    private String username;
    private String address;
    private List<Orders> ordersList;

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + ''' +
                ", address='" + address + ''' +
                ", ordersList=" + ordersList +
                '}';
    }

    public int getId() {
        return id;
    }

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

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    public List<Orders> getOrdersList() {
        return ordersList;
    }

    public void setOrdersList(List<Orders> ordersList) {
        this.ordersList = ordersList;
    }
}

7.创建实体类：Orders:

package cn.hdc.pojo;

public class Orders {
    private int id;
    private String number;
    private int userId;

    @Override
    public String toString() {
        return "Orders{" +
                "id=" + id +
                ", number='" + number + ''' +
                ", userId=" + userId +
                '}';
    }

    public int getId() {
        return id;
    }

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

    public String getNumber() {
        return number;
    }

    public void setNumber(String number) {
        this.number = number;
    }

    public int getUserId() {
        return userId;
    }

    public void setUserId(int userId) {
        this.userId = userId;
    }
}

8.创建接口OrdersMapper:

package cn.hdc.mapper;

import cn.hdc.pojo.Orders;
import org.apache.ibatis.annotations.Result;
import org.apache.ibatis.annotations.Results;
import org.apache.ibatis.annotations.Select;

import java.util.List;

public interface OrdersMapper {
    @Select("select * from tb_orders where user_id = #{uid}")
    @Results({
            @Result(id = true, property = "id", column = "id"),
            @Result(property = "number",column = "number"),
            @Result(property = "userId",column = "user_id")
    })
    public List<Orders> selectOrdersByUserId(int uid);
}

9.创建接口：UserMapper

package cn.hdc.mapper;

import cn.hdc.pojo.User;
import org.apache.ibatis.annotations.*;

public interface UserMapper {
    @Select("select * from tb_user where id = #{id}")
    @Results({
            @Result(id = true,property = "id",column = "id"),
            @Result(property = "username",column = "username"),
            @Result(property = "address",column = "address"),
            @Result(property = "ordersList",column = "id",many = @Many(select = "cn.hdc.mapper.OrdersMapper.selectOrdersByUserId"))
    })
    public User selectUserById(int id);
}

10.创建测试类：UserMapperTest:

package cn.hdc.mapper;

import cn.hdc.pojo.User;
import cn.hdc.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import static org.junit.Assert.*;

public class UserMapperTest {
    private SqlSession session;

    private UserMapper userMapper;

    @Before
    public void setUp() throws Exception {
        session = MybatisUtils.getSession();
    }

    @After
    public void tearDown() throws Exception {
        session.commit();
        session.close();
    }

    @Test
    public void selectUserById() {
        userMapper = session.getMapper(UserMapper.class);
        User user = userMapper.selectUserById(1);
        System.out.println(user);
    }
}

11.项目结构：

12.运行结果：

多对多查询

多对多关联使用中间表：

  • 在数据库中，表与表之间的多对多关联关系通常使用一个中间表来维护  

 1.pom.xml

<?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>_20230503</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>5.2.3.RELEASE</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-beans</artifactId>
            <version>5.2.3.RELEASE</version>
        </dependency>

        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.2</version>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.11</version>
        </dependency>

        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>
    </dependencies>

</project>

2.建库建表：

tb_orders表：

CREATE TABLE `tb_orders` (
  `id` int(32) NOT NULL AUTO_INCREMENT,
  `number` varchar(32) NOT NULL,
  `user_id` int(32) NOT NULL,
  PRIMARY KEY (`id`),
  KEY `user_id` (`user_id`),
  CONSTRAINT `tb_orders_ibfk_1` FOREIGN KEY (`user_id`) REFERENCES `tb_user` (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8mb4

tb_product表：

CREATE TABLE `tb_product` (
  `id` int(32) NOT NULL AUTO_INCREMENT,
  `name` varchar(32) DEFAULT NULL,
  `price` double DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8mb4

 tb_ordersitem表：

CREATE TABLE `tb_ordersitem` (
  `id` int(32) NOT NULL AUTO_INCREMENT,
  `orders_id` int(32) DEFAULT NULL,
  `product_id` int(32) DEFAULT NULL,
  PRIMARY KEY (`id`),
  KEY `orders_id` (`orders_id`),
  KEY `product_id` (`product_id`),
  CONSTRAINT `tb_ordersitem_ibfk_1` FOREIGN KEY (`orders_id`) REFERENCES `tb_orders` (`id`),
  CONSTRAINT `tb_ordersitem_ibfk_2` FOREIGN KEY (`product_id`) REFERENCES `tb_product` (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8mb4

3.创建实体类：Orders:

package cn.hdc.pojo;

import java.util.List;

public class Orders {
    private int id;
    private String number;
    private int userId;
    private List<Product> productList;

    @Override
    public String toString() {
        return "Orders{" +
                "id=" + id +
                ", number='" + number + ''' +
                ", userId=" + userId +
                ", productList=" + productList +
                '}';
    }

    public int getId() {
        return id;
    }

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

    public String getNumber() {
        return number;
    }

    public void setNumber(String number) {
        this.number = number;
    }

    public int getUserId() {
        return userId;
    }

    public void setUserId(int userId) {
        this.userId = userId;
    }

    public List<Product> getProductList() {
        return productList;
    }

    public void setProductList(List<Product> productList) {
        this.productList = productList;
    }
}

4.创建实体类：Product

package cn.hdc.pojo;

import java.util.List;

public class Product {
    private int id;
    private String name;
    private double price;
    private List<Orders> ordersList;

    @Override
    public String toString() {
        return "Product{" +
                "id=" + id +
                ", name='" + name + ''' +
                ", price=" + price +
                ", ordersList=" + ordersList +
                '}';
    }

    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 double getPrice() {
        return price;
    }

    public void setPrice(double price) {
        this.price = price;
    }

    public List<Orders> getOrdersList() {
        return ordersList;
    }

    public void setOrdersList(List<Orders> ordersList) {
        this.ordersList = ordersList;
    }
}

5.创建接口OrdersMapper

package cn.hdc.mapper;

import cn.hdc.pojo.Orders;
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 OrdersMapper {
//    @Select("select * from tb_orders where user_id = #{uid}")
//    @Results({
//            @Result(id = true, property = "id", column = "id"),
//            @Result(property = "number", column = "number"),
//            @Result(property = "userId", column = "user_id")
//    })
//    public List<Orders> selectOrdersByUserId(int uid);

    @Select("select * from tb_orders where id = #{id}")
    @Results({
            @Result(id = true, column = "id", property = "id"),
            @Result(column = "number", property = "number"),
            @Result(column = "id", property = "productList", many = @Many(select = "cn.hdc.mapper.ProductMapper.selectProductsByOrdersId"))
    })
    public Orders selectOrderById(int id);
}

6.创建接口：ProductMapper

package cn.hdc.mapper;

import cn.hdc.pojo.Product;
import org.apache.ibatis.annotations.Select;

import java.util.List;

public interface ProductMapper {
    @Select("select * from tb_product where id in (select product_id from tb_ordersitem where orders_id=#{orderId})")
    public List<Product> selectProductsByOrdersId(int orderId);
}

7.创建工具类MybatisUtils

package cn.hdc.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 {
    private static SqlSessionFactory sqlSessionFactory = null;
 
    static {
        try {
            Reader reader = Resources.getResourceAsReader("mybatis-config.xml");
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }
 
    public static SqlSession getSession() {
        return sqlSessionFactory.openSession();
    }
}

8.db.properties

driver.driver=com.mysql.cj.jdbc.Driver
driver.url=jdbc:mysql://localhost:3306/mybatis?serverTimezone=UTC&characterEncoding=utf8&useUnicode=true&useSSL=false
driver.username=root
driver.password=666666

9.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>
    <!-- 环境配置 -->
    <!-- 加载类路径下的属性文件 -->
    <properties resource="db.properties"/>

    <!-- 数据库连接相关配置 ,db.properties文件中的内容-->
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${driver.driver}"/>
                <property name="url" value="${driver.url}"/>
                <property name="username" value="${driver.username}"/>
                <property name="password" value="${driver.password}"/>
            </dataSource>
        </environment>
    </environments>
    
    <mappers>
        <package name="cn.hdc.mapper"/>
    </mappers>
</configuration>

10.创建测试类OrdersMapperTest

package cn.hdc.mapper;

import cn.hdc.pojo.Orders;
import cn.hdc.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import static org.junit.Assert.*;

public class OrdersMapperTest {
    private SqlSession session;
    private OrdersMapper ordersMapper;

    @Before
    public void setUp() throws Exception {
        session = MybatisUtils.getSession();
    }

    @After
    public void tearDown() throws Exception {
        session.commit();
        session.close();
    }

    @Test
    public void selectOrderById() {
        ordersMapper = session.getMapper(OrdersMapper.class);
        Orders orders = ordersMapper.selectOrderById(1);
        System.out.println(orders);
    }
}

11.项目结构：

12.运行结果：

案例:基于MyBatis注解的学生管理程序

代码示例：

需求：

1.pom.xml

<?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>_20230503_1</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>5.2.3.RELEASE</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-beans</artifactId>
            <version>5.2.3.RELEASE</version>
        </dependency>

        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.2</version>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.11</version>
        </dependency>

        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>
    </dependencies>
</project>

2.db.properties

driver.driver=com.mysql.cj.jdbc.Driver
driver.url=jdbc:mysql://localhost:3306/mybatis?serverTimezone=UTC&characterEncoding=utf8&useUnicode=true&useSSL=false
driver.username=root
driver.password=666666

3.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>
    <!-- 环境配置 -->
    <!-- 加载类路径下的属性文件 -->
    <properties resource="db.properties"/>

    <!-- 数据库连接相关配置 ,db.properties文件中的内容-->
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${driver.driver}"/>
                <property name="url" value="${driver.url}"/>
                <property name="username" value="${driver.username}"/>
                <property name="password" value="${driver.password}"/>
            </dataSource>
        </environment>
    </environments>
    
    <mappers>
        <package name="cn.hdc.mapper"/>
    </mappers>
</configuration>

4.MyBatisUtils工具类：

package cn.hdc.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 {
    private static SqlSessionFactory sqlSessionFactory = null;
 
    static {
        try {
            Reader reader = Resources.getResourceAsReader("mybatis-config.xml");
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }
 
    public static SqlSession getSession() {
        return sqlSessionFactory.openSession();
    }
}

5.建库建表：

s_student表:

CREATE TABLE `s_student` (
  `id` int(32) NOT NULL AUTO_INCREMENT,
  `name` varchar(40) DEFAULT NULL,
  `age` int(11) DEFAULT NULL,
  `cid` int(32) NOT NULL,
  PRIMARY KEY (`id`),
  KEY `cid` (`cid`),
  CONSTRAINT `s_student_ibfk_1` FOREIGN KEY (`cid`) REFERENCES `c_class` (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8mb4

c_class表：

CREATE TABLE `c_class` (
  `id` int(32) NOT NULL AUTO_INCREMENT,
  `classname` varchar(40) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8mb4

6.创建接口StudentMapper:

package cn.hdc.mapper;

import cn.hdc.pojo.Student;
import org.apache.ibatis.annotations.Result;
import org.apache.ibatis.annotations.Results;
import org.apache.ibatis.annotations.Select;
import org.apache.ibatis.annotations.Update;

import java.util.List;

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

    @Update("update s_student set name=#{name},age=#{age} where id=#{id}")
    public int updateStudent(Student student);

    @Select("select * from s_student where cid = #{cid}")
    @Results({
            @Result(id = true,column = "id",property = "id"),
            @Result(column = "name",property = "name"),
            @Result(column = "age",property = "age")
    })
    public List<Student> selectStudentsByCid(int cid);
}

7.创建ClassMapper接口：

package cn.hdc.mapper;

import cn.hdc.pojo.IClass;
import org.apache.ibatis.annotations.Many;
import org.apache.ibatis.annotations.Result;
import org.apache.ibatis.annotations.Results;
import org.apache.ibatis.annotations.Select;

public interface ClassMapper {
    @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",many = @Many(select = "cn.hdc.mapper.StudentMapper.selectStudentsByCid"))
    })
    public IClass selectClassById(int id);
}

8.创建StudentMapperTest:

package cn.hdc.mapper;

import cn.hdc.pojo.Student;
import cn.hdc.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import static org.junit.Assert.*;

public class StudentMapperTest {
    private SqlSession session;

    @Before
    public void setUp() throws Exception {
        session = MybatisUtils.getSession();
    }

    @After
    public void tearDown() throws Exception {
        session.commit();
        session.close();
    }

    @Test
    public void selectStudent() {
        StudentMapper studentMapper = session.getMapper(StudentMapper.class);
        Student student = studentMapper.selectStudent(2);
        System.out.println(student);
    }

    @Test
    public void updateStudent() {
        StudentMapper studentMapper = session.getMapper(StudentMapper.class);
        Student student = new Student();
        student.setName("Tom");
        student.setAge(23);
        student.setId(4);
        int ret = studentMapper.updateStudent(student);
        if (ret > 0) {
            System.out.println("添加成功！");
        } else {
            System.out.println("添加失败！");
        }
    }
}

9.创建ClassMapperTest测试类：

package cn.hdc.mapper;

import cn.hdc.pojo.IClass;
import cn.hdc.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import static org.junit.Assert.*;

public class ClassMapperTest {
    private SqlSession session;

    @Before
    public void setUp() throws Exception {
        session = MybatisUtils.getSession();
    }

    @After
    public void tearDown() throws Exception {
        session.commit();
        session.close();
    }

    @Test
    public void selectClassById() {
        ClassMapper classMapper = session.getMapper(ClassMapper.class);
        IClass iClass = classMapper.selectClassById(2);
        System.out.println(iClass);
    }
}

10.项目结构：

风语者！平时喜欢研究各种技术，目前在从事后端开发工作，热爱生活、热爱工作。

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