MapStruct 简化映射

简化 Java bean 类型之间映射

学习视频链接：https://www.bilibili.com/video/BV1E5411n7HR?from=search&seid=9468054775434592661&spm_id_from=333.337.0.0

​

1 使用

		<dependency>
            <groupId>org.mapstruct</groupId>
            <artifactId>mapstruct</artifactId>
            <version>1.3.1.Final</version>
        </dependency>

        <dependency>
            <groupId>org.mapstruct</groupId>
            <artifactId>mapstruct-processor</artifactId>
            <version>1.3.1.Final</version>
        </dependency>

...
<properties>
    <org.mapstruct.version>1.4.2.Final</org.mapstruct.version>
</properties>
...
<dependencies>
    <dependency>
        <groupId>org.mapstruct</groupId>
        <artifactId>mapstruct</artifactId>
        <version>${org.mapstruct.version}</version>
    </dependency>
</dependencies>
...
<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>3.8.1</version>
            <configuration>
                <source>1.8</source>
                <target>1.8</target>
                <annotationProcessorPaths>
                    <path>
                        <groupId>org.mapstruct</groupId>
                        <artifactId>mapstruct-processor</artifactId>
                        <version>${org.mapstruct.version}</version>
                    </path>
                </annotationProcessorPaths>
            </configuration>
        </plugin>
    </plugins>
</build>
...

可以创建interface或者abstract class

package com.example.demo.mapper;

import com.example.demo.pojo.User;
import com.example.demo.pojo.UserRoleDto;
import org.mapstruct.Mapper;
import org.mapstruct.Mapping;
import org.mapstruct.Mappings;
import org.mapstruct.factory.Mappers;

/**
 * @Author gett
 * @Date 2021/12/28  10:33
 * @Description MapStruct对象属性转换接口
 */
@Mapper
public interface UserRoleMapper {

    //ClassLoader 加载方式
    UserRoleMapper INSTANCE=Mappers.getMapper(UserRoleMapper.class);

    @Mappings({
            @Mapping(source = "id", target = "id"),
            @Mapping(source = "username", target = "username"),
            @Mapping(source = "role.roleName", target = "roleName")
    })
    UserRoleDto toUserRoleDto(User user);

}

package com.example.demo.mapper;

import com.example.demo.pojo.User;
import com.example.demo.pojo.UserRoleDto;
import org.mapstruct.Mapper;
import org.mapstruct.factory.Mappers;

/**
 * @Author gett
 * @Date 2021/12/28  10:33
 * @Description MapStruct对象属性转换接口
 */
@Mapper
public abstract class UserRoleMapper {

    //ClassLoader 加载方式
    public static UserRoleMapper INSTANCE=Mappers.getMapper(UserRoleMapper.class);
    
    public  abstract   UserRoleDto toUserRoleDto(User user);
    
}

2 @Mapper

• 同类型且同名的属性会自动映射
• MapStruct会自动类型转换
  • 8种基本类型和他们对应的包装类型之间
  • 8种基本类型（包括他们的包装类型）和string之间
  • 日期类型和string之间

3 @Mappings与@Mapping

• 指定属性之间的映射关系
  • 日期格式化：dateFormat = "yyyy-MM-dd HH:mm:ss"
  • 数字格式化：numberFormat = "#.00"
• source或target多余的属性对方没有，不会报错
• ignore
• 引用对象的映射处理
• 批量映射

4 @MappingTarget和@AfterMapping

在映射最后一步对属性的自定义映射处理
@MappingTarget：表明传来的对象是已经赋过值的
@AfterMapping：表示让MapStruct在调用完自动转换的方法之后，会来自动调用本方法
​

package com.example.demo.mapper;

import com.example.demo.pojo.*;
import org.mapstruct.*;
import org.mapstruct.factory.Mappers;
import org.springframework.util.StringUtils;

/**
 * @Author gett
 * @Date 2021/12/28  10:33
 * @Description MapStruct对象属性转换接口
 */
@Mapper
public abstract class UserRoleMapper {

    //ClassLoader 加载方式
    public static  UserRoleMapper INSTANCE=Mappers.getMapper(UserRoleMapper.class);

    public  abstract UserRoleDto toUserRoleDto(User user);

    @AfterMapping
        //表示让MapStruct在调用完自动转换的方法之后，会来自动调用本方法
    void after(User user, @MappingTarget UserRoleDto userRoleDto) {
        //@MappingTarget：表明传来的对象是已经赋过值的

        String username = user.getUsername();
        if (username != null && !StringUtils.isEmpty(username)){
            userRoleDto.setRoleName(username);
        }

    }

}

5 批量转换

package com.example.demo.mapper;

import com.example.demo.pojo.*;
import org.mapstruct.*;
import org.mapstruct.factory.Mappers;
import org.springframework.util.StringUtils;

import java.util.List;

/**
 * @Author gett
 * @Date 2021/12/28  10:33
 * @Description MapStruct对象属性转换接口
 */
@Mapper
public abstract class UserRoleMapper {

    //ClassLoader 加载方式
    public static  UserRoleMapper INSTANCE=Mappers.getMapper(UserRoleMapper.class);

    //集合批量转换
    public  abstract List<UserRoleDto> toListDto(List<User> user);

}

package com.example.demo.test;

import com.example.demo.mapper.UserRoleMapper;
import com.example.demo.pojo.Role;
import com.example.demo.pojo.User;
import com.example.demo.pojo.UserRoleDto;

import java.util.ArrayList;
import java.util.List;

/**
 * @Author gett
 * @Date 2021/12/28  10:23
 * @Description 测试类
 */
public class Test {

    public static void main(String[] args) {
        Role role = new Role(2L, "administrator", "用户");
        User user1 = new User(1001L,"张三","123456","15222222222","[email protected]",role);
        User user2 = new User(1002L,"李四","123456","15222222222","[email protected]",role);
        User user3 = new User(1003L,"王五","123456","15222222222","[email protected]",role);

        List<User> users = new ArrayList<>();
        users.add(user1);
        users.add(user2);
        users.add(user3);

        List<UserRoleDto> dto = UserRoleMapper.INSTANCE.toListDto(users);
        System.out.println(dto);

    }

}

6 @BeanMapping

ignoreByDefault ：忽略MapStruct的默认映射行为。只映射那些@Mapping设置了的属性避免不需要的赋值、避免属性覆盖
​

@BeanMapping(ignoreByDefault = true)
@Mapping(source = "id", target = "id")
public  abstract Ids toIds(User user);

Role role = new Role(2L, "administrator", "用户");
User user1 = new User(1001L,"张三","123456","15222222222","[email protected]",role);



Ids ids = UserRoleMapper.INSTANCE.toIds(user1);
System.out.println("---"+ids);
输出：---Ids(id=1001, username=null)

7 @InheritConfiguration

更新的场景
​

@BeanMapping(ignoreByDefault = true)
@Mapping(source = "id", target = "id")
@Mapping(source = "username", target = "username")
public  abstract Ids toIds(User user);


@InheritConfiguration
@Mapping(target = "id", ignore = true)
public  abstract void toUpdate(User user, @MappingTarget Ids Ids) ;

package com.example.demo.test;

import com.example.demo.mapper.UserRoleMapper;
import com.example.demo.pojo.Ids;
import com.example.demo.pojo.Role;
import com.example.demo.pojo.User;
import com.example.demo.pojo.UserRoleDto;

import java.util.ArrayList;
import java.util.List;

/**
 * @Author gett
 * @Date 2021/12/28  10:23
 * @Description 测试类
 */
public class Test {

    public static void main(String[] args) {
        Role role = new Role(2L, "administrator", "用户");
        User user1 = new User(1001L,"zhangsan","123456","null","[email protected]",role);

        Ids ids = UserRoleMapper.INSTANCE.toIds(user1);
        System.out.println(ids);

        User user2 = new User();
        user2.setUsername("lisi");
        System.out.println(user2);

        //通过user2的属性来更新已经存在的对象
        UserRoleMapper.INSTANCE.toUpdate(user2,ids);
        System.out.println(ids);
    }
}

输出：
Ids(id=1001, username=zhangsan, phoneNum=null)
User(id=null, username=lisi, password=null, phoneNum=null, email=null, role=null)
Ids(id=1001, username=lisi, phoneNum=null)

8 @InheritInverseConfiguration

反向映射。只继承@Mapping注解配置，不会继承@BeanMapping
name：指定使用哪一个方法的配置，写方法的名字
​

@BeanMapping(ignoreByDefault = true)
@Mapping(source = "id", target = "id")
@Mapping(source = "username", target = "username")
public  abstract Ids toIds(User user);


@BeanMapping(ignoreByDefault = true)
@InheritInverseConfiguration(name = "toIds")
public  abstract User inverse(Ids ids);

package com.example.demo.test;

import com.example.demo.mapper.UserRoleMapper;
import com.example.demo.pojo.Ids;
import com.example.demo.pojo.Role;
import com.example.demo.pojo.User;
import com.example.demo.pojo.UserRoleDto;

import java.util.ArrayList;
import java.util.List;

/**
 * @Author gett
 * @Date 2021/12/28  10:23
 * @Description 测试类
 */
public class Test {

    public static void main(String[] args) {

        Ids ids = new Ids(1001L,"zhangsan","15222222222");
        System.out.println(ids);
        User user = UserRoleMapper.INSTANCE.inverse(ids);
        System.out.println(user);

    }


}

输出：
Ids(id=1001, username=zhangsan, phoneNum=15222222222)
User(id=1001, username=zhangsan, password=null, phoneNum=null, email=null, role=null)

mapper层
@Component
@Mapper
public abstract class UserRoleMapper {
	//ClassLoader 加载方式
    public static  UserRoleMapper INSTANCE=Mappers.getMapper(UserRoleMapper.class);
}

controller层
@Resource
private UserRoleMapper userRoleMapper;