Java 实体映射工具 MapStruct

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原文链接：https://blog.csdn.net/zhige_me/article/details/80699784

maven依赖引入方式

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
   <modelVersion>4.0.0</modelVersion>
   <parent>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-parent</artifactId>
      <version>2.5.5</version>
      <relativePath/> <!-- lookup parent from repository -->
   </parent>
   <groupId>com.laoxu</groupId>
   <artifactId>map-struct-demo</artifactId>
   <version>1.0</version>
   <name>mapstructdemo</name>
   <description>mapstructdemo</description>
   <properties>
      <java.version>1.8</java.version>
      <mapstruct.version>1.2.0.Final</mapstruct.version>
   </properties>
   <dependencies>
      <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-web</artifactId>
      </dependency>

      <dependency>
         <groupId>org.mapstruct</groupId>
         <artifactId>mapstruct-jdk8</artifactId>
         <version>${mapstruct.version}</version>
      </dependency>
      <dependency>
         <groupId>org.mapstruct</groupId>
         <artifactId>mapstruct-processor</artifactId>
         <version>${mapstruct.version}</version>
      </dependency>

      <dependency>
         <groupId>org.projectlombok</groupId>
         <artifactId>lombok</artifactId>
         <optional>true</optional>
      </dependency>

   </dependencies>

   <build>
      <plugins>
         <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
         </plugin>
         <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>3.8.1</version>
            <configuration>
               <source>8</source>
               <target>8</target>
               <encoding>UTF-8</encoding>
               <annotationProcessorPaths>
                  <path>
                     <groupId>org.mapstruct</groupId>
                     <artifactId>mapstruct-processor</artifactId>
                     <version>1.2.0.Final</version>
                  </path>
                  <path>
                     <groupId>org.projectlombok</groupId>
                     <artifactId>lombok</artifactId>
                     <version>1.18.12</version>
                  </path>
               </annotationProcessorPaths>
            </configuration>
         </plugin>
      </plugins>
   </build>


</project>

注意：maven插件中的mapstruct-processor版本号一定要跟依赖中的mapstruct-processor版本号一致，否则报错

1、定义Person类和User类

package com.laoxu.mapstructdemo.DO;

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

import java.util.Date;

@NoArgsConstructor
@AllArgsConstructor
@Data
public class Person {
    private Long id;
    private String name;
    private String email;
    private Date birthday;
    private User user;
}

package com.laoxu.mapstructdemo.DO;


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

@NoArgsConstructor
@AllArgsConstructor
@Data
public class User {
    private Integer age;
}

2、定义一个映射接收的dto类

package com.laoxu.mapstructdemo.dto;

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

import java.util.Date;

@NoArgsConstructor
@AllArgsConstructor
@Data
public class PersonDTO {
    private Long id;
    private String name;
    /**
     * 对应 Person.user.age
     */
    private Integer age;
    private String email;
    /**
     * 与 DO 里面的字段名称(birthDay)不一致
     */
    private Date birth;
    /**
     * 对 DO 里面的字段(birthDay)进行拓展,dateFormat 的形式
     */
    private String birthDateFormat;
    /**
     * 对 DO 里面的字段(birthDay)进行拓展,expression 的形式
     */
    private String birthExpressionFormat;

}

3、定义一个日期转换工具类

package com.laoxu.mapstructdemo.util;

import java.text.SimpleDateFormat;
import java.util.Date;

public class DateUtils {

    public static String dateToString(Date date) {
        return new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(date);
    }
}

4、定义关键的转换映射接口

package com.laoxu.mapstructdemo.convert;

import com.laoxu.mapstructdemo.DO.Person;
import com.laoxu.mapstructdemo.dto.PersonDTO;
import org.mapstruct.Mapper;
import org.mapstruct.Mapping;
import org.mapstruct.Mappings;
import org.mapstruct.factory.Mappers;

import java.util.List;

@Mapper(componentModel = "spring")
public interface PersonConverter {
    PersonConverter INSTANCE = Mappers.getMapper(PersonConverter.class);
    @Mappings({
        @Mapping(source = "birthday", target = "birth"),
        @Mapping(source = "birthday", target = "birthDateFormat", dateFormat = "yyyy-MM-dd HH:mm:ss"),
        @Mapping(target = "birthExpressionFormat", expression = "java(com.laoxu.mapstructdemo.util.DateUtils.dateToString(person.getBirthday()))"),
        @Mapping(source = "user.age", target = "age"),
        @Mapping(target = "email", ignore = true)
    })
    PersonDTO domain2dto(Person person);

    List<PersonDTO> domain2dto(List<Person> people);
}

• source为接口方法参数对象中的属性
• target为接口返回对象中的属性
• expression返回对象中根据表达式中的方法转换后的属性

5、在springboot项目中启动测试

package com.laoxu.mapstructdemo;

import com.laoxu.mapstructdemo.DO.Person;
import com.laoxu.mapstructdemo.DO.User;
import com.laoxu.mapstructdemo.convert.PersonConverter;
import com.laoxu.mapstructdemo.dto.PersonDTO;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
import java.util.Objects;

@SpringBootApplication
public class MapstructdemoApplication {

   public static void main(String[] args) {
      SpringApplication.run(MapstructdemoApplication.class, args);
      Person person = new Person(1L,"zhige","zhige.me@gmail.com",new Date(),new User(1));
      PersonDTO personDTO = PersonConverter.INSTANCE.domain2dto(person);
      System.out.println(personDTO);
      System.out.println(Objects.equals(personDTO.getId(), person.getId()));
      System.out.println(Objects.equals(personDTO.getName(), person.getName()));
      System.out.println(Objects.equals(personDTO.getBirth(), person.getBirthday()));
      String format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(personDTO.getBirth());
      System.out.println(Objects.equals(personDTO.getBirthDateFormat(),format));
      System.out.println(Objects.equals(personDTO.getBirthExpressionFormat(),format));

      List<Person> people = new ArrayList<>();
      people.add(person);
      List<PersonDTO> personDTOs = PersonConverter.INSTANCE.domain2dto(people);
      System.out.println(personDTOs);
   }

}

6、查看结果

PersonDTO(id=1, name=zhige, age=1, email=null, birth=Fri Oct 08 11:01:48 CST 2021, birthDateFormat=2021-10-08 11:01:48, birthExpressionFormat=2021-10-08 11:01:48)
true
true
true
true
true
[PersonDTO(id=1, name=zhige, age=1, email=null, birth=Fri Oct 08 11:01:48 CST 2021, birthDateFormat=2021-10-08 11:01:48, birthExpressionFormat=2021-10-08 11:01:48)]