MapStruct的使用

最近在学习技术时候，发现一个特别好用的包，org.mapstruct:mapstruct，它是专门用来处理 domin 实体类与 model 类的属性映射的

它的优势：
很多项目大量映射的方式通过手动get、set，首先写法很low，没有技术含量。而且中间还可能牵涉了很多类型转换，嵌套之类的繁琐操作，非常的麻烦。

一、导包

在项目的pom.xml 文件夹中导入包

 <!--mapStruct依赖-->
<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>
     <scope>provided</scope>
</dependency>

如果想要在代码编写的时候有很好的提示的时候，也可以在pom.xml文件中加入相应的插件

<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>3.5.1</version>
            <configuration>
                <source>1.8</source>
                <target>1.8</target>
                <annotationProcessorPaths>
                    <path>
                        <groupId>org.mapstruct</groupId>
                        <artifactId>mapstruct-processor</artifactId>
                        <version>1.3.1.Final</version>
                    </path>
                </annotationProcessorPaths>
            </configuration>
        </plugin>
    </plugins>
</build>

二、常用注解

三、代码使用

案例详解：mapstruct 实体转换及List转换
1、封装接口

package com.geesun.picking.converter;

import com.geesun.picking.domain.MacPickingDetails;
import com.geesun.picking.domain.MacPickingMain;
import com.geesun.picking.domain.MacPrepareDetails;
import com.geesun.picking.domain.MacPrepareMain;
import com.geesun.picking.domain.dto.MacPickingDTO;
import org.mapstruct.Builder;
import org.mapstruct.Mapper;
import org.mapstruct.factory.Mappers;

/**
 * pojo转换器
 *
 * @author xxx
 * @name ProcessConverter
 * @date 2023-01-05 11:43
 */
@Mapper(componentModel = "spring", builder = @Builder(disableBuilder = true))
public interface PojoConverter {

    PojoConverter INSTANCE = Mappers.getMapper(PojoConverter .class);

    /**
     * 用户实体转换用户DTO对象
     */
    UserDto toUserDto(User data);

}

2、特殊案例

@Mappings({
		@Mapping(source = "cityId", target = "cityIds"),
        @Mapping(target = "groupIds", expression = "java(com.alibaba.fastjson.JSONObject.parseObject(source.getUserGroupIds(), new com.alibaba.fastjson.TypeReference<java.util.List<java.lang.Long>>() {}))"),
        @Mapping(target = "status", ignore = true)
})
Context templateDto2Context(TemplateDto source);

(1) 类型不一致

@Mappings({
	@Mapping(target = "createTime", expression = "java(com.java.mmzsblog.util.DateTransform.strToDate(source.getCreateTime()))"),
})
UserVO3 toConvertVO3(User source);

(2) 字段名不一致

@Mappings({
	@Mapping(source = "id", target = "userId"),
    @Mapping(source = "name", target = "userName")
})
UserVO4 toConvertVO(User source);

(3) 忽略字段

@Mappings({
        @Mapping(target = "status", ignore = true)
})
Context templateDto2Context(TemplateDto source);

（4）执行报错

报错案例：Unknown property “xxx” in result type xxx. Did you mean “null”?

代码生成器annotationProcessor标签部分，将lombok放在mapstruct之前

    <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>
                    <encoding>UTF-8</encoding>
                    <!--自动生成代码annotationProcessor-->
                    <annotationProcessorPaths>
                        <path>
                            <groupId>org.projectlombok</groupId>
                            <artifactId>lombok</artifactId>
                            <version>${lombok.version}</version>
                        </path>
                        <path>
                            <groupId>org.mapstruct</groupId>
                            <artifactId>mapstruct-processor</artifactId>
                            <version>${mapstruct.version}</version>
                        </path>
                    </annotationProcessorPaths>
                </configuration>
            </plugin>
        </plugins>
    </build>

参考链接：Mapstruct使用时报Unknown property xxx in result type xxx. Did you mean null?

3、mapstruct禁用构建器@Bulder
参考文档：https://blog.csdn.net/lhc66666/article/details/123654325

在转换类上添加注解：@Mapper(builder = @Builder(disableBuilder = true))