第十章 Mybatis之注解开发

王哲晓2024-10-26 16:24

目录

一、引言

二、常规XML完成CRUD

[2.1. 用户实体类](#2.1. 用户实体类)

[2.2. UserMapper](#2.2. UserMapper)

[2.3. sqlMapConfig.xml](#2.3. sqlMapConfig.xml)

[2.4. properties](#2.4. properties)

[2.5. UserMapper.xml](#2.5. UserMapper.xml)

[2.6. 测试类](#2.6. 测试类)

三、注解完成CRUD

[3.1. UserMapper](#3.1. UserMapper)

[3.2. sqlMapConfig.xml](#3.2. sqlMapConfig.xml)

四、注解实现复杂映射开发

[4.1. 一对一查询模式（1）](#4.1. 一对一查询模式（1）)

[4.1.1. OrderMapper](#4.1.1. OrderMapper)

[4.1.2. sqlMapConfig.xml](#4.1.2. sqlMapConfig.xml)

[4.1.3. properties](#4.1.3. properties)

[4.1.4. 订单实体类](#4.1.4. 订单实体类)

[4.1.5. 用户实体类](#4.1.5. 用户实体类)

[4.1.6. 测试类](#4.1.6. 测试类)

[4.2. 一对一查询模式（2）](#4.2. 一对一查询模式（2）)

[4.3. 一对多查询模型](#4.3. 一对多查询模型)

[4.3.1. sqlMapConfig.xml](#4.3.1. sqlMapConfig.xml)

[4.3.2. properties](#4.3.2. properties)

[4.3.3. UserMapper](#4.3.3. UserMapper)

[4.3.4. OrderMapper](#4.3.4. OrderMapper)

[4.3.5. Order实体类](#4.3.5. Order实体类)

[4.3.6. User实体类](#4.3.6. User实体类)

[4.4. 多对多查询模型](#4.4. 多对多查询模型)

[4.4.1. sqlMapConfig.xml](#4.4.1. sqlMapConfig.xml)

[4.4.2. properties](#4.4.2. properties)

[4.4.3. UserMapper](#4.4.3. UserMapper)

[4.4.4. RoleMapper](#4.4.4. RoleMapper)

[4.4.5. Role实体类](#4.4.5. Role实体类)

[4.4.6. User实体类](#4.4.6. User实体类)

一、引言

MyBatis 注解开发是指在 MyBatis 中使用注解来代替 XML 配置文件的方式，通过使用注解开发方式，这样我们就可以减少编写Mapper.xml映射文件了。

@Insert：执行新增操作

@Update：执行更新操作

@Delete：执行删除操作

@Select：执行查询操作，返回查询结果。

@Result：执行结果集封装

@Results：可以与@Result 一起使用，封装多个结果集。

@One：实现一对一结果集封装

@Many：实现一对多结果集封装

二、常规XML完成CRUD

2.1. 用户实体类

java 复制代码 
package com.example.domain;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import lombok.ToString;
import java.util.Date;

@Data
@AllArgsConstructor
@NoArgsConstructor
@ToString
public class User {
    private int id;
    private String username;
    private String password;
    private Date birthday;
}

2.2. UserMapper

java 复制代码 
package com.example.mapper;

import com.example.domain.User;
import java.util.List;

public interface UserMapper {

    void save(User user);

    void update(User user);

    void delete(int id);

    User findById(int id);

    List<User> findAll();
}

2.3. sqlMapConfig.xml

XML 复制代码 
<?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>
    <!-- 加载外部properties -->
    <properties resource="jdbc.properties"></properties>

    <settings>
        <!-- 其他配置 -->
        <setting name="logImpl" value="STDOUT_LOGGING"/>
    </settings>

    <typeAliases>
        <typeAlias type="com.example.domain.User" alias="user"></typeAlias>
    </typeAliases>

    <plugins>
        <plugin interceptor="com.github.pagehelper.PageHelper">
            <!-- 指定方言 MySQl -->
            <property name="dialect" value="mysql"/>
        </plugin>
    </plugins>
    
    <!-- 数据源环境 -->
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${jdbc.username}"/>
                <property name="password" value="${jdbc.password}"/>
            </dataSource>
        </environment>
    </environments>

    <!-- 加载映射文件 -->
    <mappers>
        <mapper resource="com/example/mapper/UserMapper.xml"/>
    </mappers>
</configuration>

2.4. properties

XML 复制代码 
jdbc.driver=com.mysql.cj.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/test
jdbc.username=root
jdbc.password=Wangzhexiao

2.5. UserMapper.xml

XML 复制代码 
<?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.example.mapper.UserMapper">

    <insert id="save" parameterType="user">
        insert into user values(#{id},#{username},#{password},#{birthday})
    </insert>

    <update id="update" parameterType="user">
        update user set username = #{username}, password = #{password} where id = #{id}
    </update>

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

    <select id="findById" parameterType="int" resultType="user">
        select * from user where id = #{id}
    </select>

    <select id="findAll" resultType="user">
        select * from user
    </select>
</mapper>

2.6. 测试类

java 复制代码 
package com.example;

import com.example.domain.User;
import com.example.mapper.UserMapper;
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.Before;
import org.junit.Test;
import java.io.IOException;
import java.io.InputStream;
import java.util.Date;

public class UserTest {

    private UserMapper userMapper;

    @Before
    public void before() throws IOException {
        InputStream resourceAsStream = Resources.getResourceAsStream("sqlMapConfig.xml");
        SqlSessionFactory sqlSessionFactory = new
                SqlSessionFactoryBuilder().build(resourceAsStream);
        SqlSession sqlSession = sqlSessionFactory.openSession(true);
        userMapper = sqlSession.getMapper(UserMapper.class);
    }

    @Test
    public void insert() {
        User user = new User();
        user.setUsername("余则成");
        user.setPassword("yuzecheng");
        user.setBirthday(new Date());
        userMapper.save(user);
    }

    @Test
    public void delete() {
        userMapper.delete(11);
    }

    @Test
    public void update() {
        User user = new User();
        user.setId(1);
        user.setUsername("毛泽东");
        user.setPassword("maozedong");
        user.setBirthday(new Date());
        userMapper.update(user);
    }

    @Test
    public void findById() {
        userMapper.findById(1);
    }

    @Test
    public void findAll() {
        userMapper.findAll();
    }
}

三、注解完成CRUD

上述XML方式CRUD其他相关代码不变，我们仅删除UserMapper.xml，将其中的SQL通过注解的方式，添加到UserMapper接口中的各个对应的方法上，以及将sqlMapConfig.xml中对UserMapper.xml的配置改为UserMapper接口：

3.1. UserMapper

java 复制代码 
package com.example.mapper;

import com.example.domain.User;
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 UserMapper {

    @Insert("insert into user values(#{id},#{username},#{password},#{birthday})")
    void save(User user);

    @Update("update user set username = #{username}, password = #{password} where id = #{id}")
    void update(User user);

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

    @Select("select * from user where id = #{id}")
    User findById(int id);

    @Select("select * from user")
    List<User> findAll();
}

3.2. sqlMapConfig.xml

XML 复制代码 
<?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>
    <!-- 加载外部properties -->
    <properties resource="jdbc.properties"></properties>

    <settings>
        <!-- 其他配置 -->
        <setting name="logImpl" value="STDOUT_LOGGING"/>
    </settings>

    <typeAliases>
        <typeAlias type="com.example.domain.User" alias="user"></typeAlias>
    </typeAliases>

    <plugins>
        <plugin interceptor="com.github.pagehelper.PageHelper">
            <!-- 指定方言 MySQl -->
            <property name="dialect" value="mysql"/>
        </plugin>
    </plugins>
    
    <!-- 数据源环境 -->
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${jdbc.username}"/>
                <property name="password" value="${jdbc.password}"/>
            </dataSource>
        </environment>
    </environments>

    <!-- 加载映射关系 -->
    <mappers>
        <!-- 指定接口所在的包 -->
        <package name="com.example.mapper"/>
    </mappers>
</configuration>

查看最终控制台输出结果，效果和XML方式一样。

四、注解实现复杂映射开发

实现复杂关系映射之前我们可以在映射文件中通过配置<resultMap>来实现，使用注解开发后，我们可以使用@Results注解，@Result注解，@One注解，@Many注解组合完成复杂关系的配置。

4.1. 一对一查询模式（1）

4.1.1. OrderMapper

java 复制代码 
package com.example.mapper;

import com.example.domain.Order;
import org.apache.ibatis.annotations.Result;
import org.apache.ibatis.annotations.Results;
import org.apache.ibatis.annotations.Select;
import java.util.List;

public interface OrderMapper {

    @Select("select *, o.id oid from `order` o, user u where o.uid = u.id")
    @Results({
            @Result(column = "oid", property = "id"),
            @Result(column = "ordertime", property = "orderTime"),
            @Result(column = "total", property = "total"),
            @Result(column = "uid", property = "user.id"),
            @Result(column = "username", property = "user.username"),
            @Result(column = "password", property = "user.password"),
    })
    List<Order> findAll();
}

4.1.2. sqlMapConfig.xml

XML 复制代码 
<?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>
    <!-- 加载外部properties -->
    <properties resource="jdbc.properties"></properties>

    <settings>
        <!-- 其他配置 -->
        <setting name="logImpl" value="STDOUT_LOGGING"/>
    </settings>

    <typeAliases>
        <typeAlias type="com.example.domain.User" alias="user"></typeAlias>
    </typeAliases>

    <plugins>
        <plugin interceptor="com.github.pagehelper.PageHelper">
            <!-- 指定方言 MySQl -->
            <property name="dialect" value="mysql"/>
        </plugin>
    </plugins>
    
    <!-- 数据源环境 -->
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${jdbc.username}"/>
                <property name="password" value="${jdbc.password}"/>
            </dataSource>
        </environment>
    </environments>

    <!-- 加载映射关系 -->
    <mappers>
        <!-- 指定接口所在的包 -->
        <package name="com.example.mapper"/>
    </mappers>
</configuration>

4.1.3. properties

XML 复制代码 
jdbc.driver=com.mysql.cj.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/test
jdbc.username=root
jdbc.password=Wangzhexiao

4.1.4. 订单实体类

java 复制代码 
package com.example.domain;

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

import java.util.Date;

@Data
@AllArgsConstructor
@NoArgsConstructor
@ToString
public class Order {

    private int id;
    private Date orderTime;
    private double total;
    private User user;
}

4.1.5. 用户实体类

java 复制代码 
package com.example.domain;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import lombok.ToString;
import java.util.Date;

@Data
@AllArgsConstructor
@NoArgsConstructor
@ToString
public class User {
    private int id;
    private String username;
    private String password;
    private Date birthday;
}

4.1.6. 测试类

java 复制代码 
package com.example;

import com.example.domain.Order;
import com.example.mapper.OrderMapper;
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.Before;
import org.junit.Test;
import java.io.IOException;
import java.io.InputStream;
import java.util.List;

public class UserTest {

    private OrderMapper orderMapper;

    @Before
    public void before() throws IOException {
        InputStream resourceAsStream = Resources.getResourceAsStream("sqlMapConfig.xml");
        SqlSessionFactory sqlSessionFactory = new
                SqlSessionFactoryBuilder().build(resourceAsStream);
        SqlSession sqlSession = sqlSessionFactory.openSession(true);
        orderMapper = sqlSession.getMapper(OrderMapper.class);
    }

    @Test
    public void findAll() {
        List<Order> orders = orderMapper.findAll();
        for (Order order : orders) {
            System.out.println(order);
        }
    }
}

4.2. 一对一查询模式（2）

我们在一对一查询模式（1）的OrderMapper接口方法上做适当调整：

java 复制代码 
package com.example.mapper;

import com.example.domain.Order;
import com.example.domain.User;
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 OrderMapper {

    @Select("select * from `order`")
    @Results({
            @Result(column = "oid", property = "id"),
            @Result(column = "ordertime", property = "orderTime"),
            @Result(column = "total", property = "total"),
            @Result(
                    property = "user", // 要封装的属性名称
                    column = "uid", // 根据这个字段去查询user表的数据
                    javaType = User.class, // 要封装的实体类型
                    // select属性代表查询这个接口的方法获得数据
                    one = @One(select = "com.example.mapper.UserMapper.findById")
            )
    })
    List<Order> findAll();
}

4.3. 一对多查询模型

4.3.1. sqlMapConfig.xml

XML 复制代码 
<?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>
    <!-- 加载外部properties -->
    <properties resource="jdbc.properties"></properties>

    <settings>
        <!-- 其他配置 -->
        <setting name="logImpl" value="STDOUT_LOGGING"/>
    </settings>

    <typeAliases>
        <typeAlias type="com.example.domain.User" alias="user"></typeAlias>
    </typeAliases>

    <plugins>
        <plugin interceptor="com.github.pagehelper.PageHelper">
            <!-- 指定方言 MySQl -->
            <property name="dialect" value="mysql"/>
        </plugin>
    </plugins>
    
    <!-- 数据源环境 -->
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${jdbc.username}"/>
                <property name="password" value="${jdbc.password}"/>
            </dataSource>
        </environment>
    </environments>

    <!-- 加载映射关系 -->
    <mappers>
        <!-- 指定接口所在的包 -->
        <package name="com.example.mapper"/>
    </mappers>
</configuration>

4.3.2. properties

XML 复制代码 
jdbc.driver=com.mysql.cj.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/test
jdbc.username=root
jdbc.password=Wangzhexiao

4.3.3. UserMapper

java 复制代码 
package com.example.mapper;

import com.example.domain.User;
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 UserMapper {

    @Select("select * from user")
    @Results({
            @Result(column = "id", property = "id"),
            @Result(column = "username", property = "username"),
            @Result(column = "password", property = "password"),
            @Result(
                    property = "orderList", // 要封装的属性名称
                    column = "id", // 根据这个字段去查询订单表的数据
                    javaType = List.class, // 要封装的实体类型
                    // select属性代表查询这个接口的方法获得数据
                    many = @Many(select = "com.example.mapper.OrderMapper.findByUid")
            )
    })
    List<User> findUserAndOrderAll();
}

4.3.4. OrderMapper

java 复制代码 
package com.example.mapper;

import com.example.domain.Order;
import org.apache.ibatis.annotations.Select;
import java.util.List;

public interface OrderMapper {

    @Select("select * from `order` where uid = #{uid}")
    List<Order> findByUid(int uid);
}

4.3.5. Order实体类

java 复制代码 
package com.example.domain;

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

import java.util.Date;

@Data
@AllArgsConstructor
@NoArgsConstructor
@ToString
public class Order {

    private int id;
    private Date orderTime;
    private double total;
    private User user;
}

4.3.6. User实体类

java 复制代码 
package com.example.domain;

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

import java.util.Date;

@Data
@AllArgsConstructor
@NoArgsConstructor
@ToString
public class Order {

    private int id;
    private Date orderTime;
    private double total;
    private User user;
}

4.4. 多对多查询模型

4.4.1. sqlMapConfig.xml

XML 复制代码 
<?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>
    <!-- 加载外部properties -->
    <properties resource="jdbc.properties"></properties>

    <settings>
        <!-- 其他配置 -->
        <setting name="logImpl" value="STDOUT_LOGGING"/>
    </settings>

    <typeAliases>
        <typeAlias type="com.example.domain.User" alias="user"></typeAlias>
    </typeAliases>

    <plugins>
        <plugin interceptor="com.github.pagehelper.PageHelper">
            <!-- 指定方言 MySQl -->
            <property name="dialect" value="mysql"/>
        </plugin>
    </plugins>
    
    <!-- 数据源环境 -->
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${jdbc.username}"/>
                <property name="password" value="${jdbc.password}"/>
            </dataSource>
        </environment>
    </environments>

    <!-- 加载映射关系 -->
    <mappers>
        <!-- 指定接口所在的包 -->
        <package name="com.example.mapper"/>
    </mappers>
</configuration>

4.4.2. properties

XML 复制代码 
jdbc.driver=com.mysql.cj.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/test
jdbc.username=root
jdbc.password=Wangzhexiao

4.4.3. UserMapper

java 复制代码 
package com.example.mapper;

import com.example.domain.User;
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 UserMapper {

    @Select("select * from user")
    @Results({
            @Result(column = "id", property = "id"),
            @Result(column = "username", property = "username"),
            @Result(column = "password", property = "password"),
            @Result(
                    property = "roleList", // 要封装的属性名称
                    column = "id", // 根据这个字段去查询角色表的数据
                    javaType = List.class, // 要封装的实体类型
                    // select属性代表查询这个接口的方法获得数据
                    many = @Many(select = "com.example.mapper.RoleMapper.findByUid")
            )
    })
    List<User> findUserAndRoleAll();
}

4.4.4. RoleMapper

java 复制代码 
package com.example.mapper;

import com.example.domain.Role;
import org.apache.ibatis.annotations.Select;

import java.util.List;

public interface RoleMapper {
    @Select("select * from user_role ur, role r where ur.role_id = r.id and ur.user_id = #{uid}")
    List<Role> findByUid(int uid);
}

4.4.5. Role实体类

java 复制代码 
package com.example.domain;

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

@Data
@AllArgsConstructor
@NoArgsConstructor
public class Role {
    private int id;
    private String roleName;
    private String roleDesc;
}

4.4.6. User实体类

java 复制代码 
package com.example.domain;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import lombok.ToString;
import java.util.Date;
import java.util.List;

@Data
@AllArgsConstructor
@NoArgsConstructor
@ToString
public class User {
    private int id;
    private String username;
    private String password;
    private Date birthday;
    // 描述当前用户具有多个角色
    private List<Role> roleList;
}
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