Bean映射工具MapStruct介绍

Love The Way You Lie 2022-11-07 13:27 194阅读 0赞

# 1. MapStruct是什么 #

MapStruct是一个功能强大且性能很高的Bean映射工具，项目开发中难免会涉及各种Bean的转换，DTO->VO->Entity。  
市面上能做转换的框架很多，以前我们常用的可能是`BeanUtils.copyProperties`，其核心是在运行时根据反射动态赋值。动态方案的缺陷在于大量的反射调用，性能比较差，内存占用多，不适合特别高并发的应用场景。  
而MapStruct通过注解，在编译时静态生成映射代码，其最终编译出来的代码和手写的代码在性能上完全一致，且有强大的注解等能力。如果你的IDE支持，甚至可以在编译后看到编译出来的映射代码，用来做check。

下面给出一张性能对比.  
![在这里插入图片描述][20210312152710383.png]  
很明显MapStruct和JMapper的性能是最优异的

# 2. MapStruct如何使用 #

![.][]  
.如果报错可以尝试不要使用Lombok注解

## 2.1 基础使用 ##

**2.1.1 导包**

<dependency>
        <groupId>org.mapstruct</groupId>
        <artifactId>mapstruct</artifactId>
        <version>1.4.2.Final</version>
    </dependency>
    
    <dependency>
        <groupId>org.apache.commons</groupId>
        <artifactId>commons-lang3</artifactId>
        <version>3.7</version>
    </dependency>

`commons-lang3`不是必须的，此处只是为了演示

**2.1.2 写几个测试类**  
Person

package com.bxoon.mapstruct;
    
    
    import java.util.Date;
    
    public class Person { 
        private Long id;
        private String name;
        private String email;
        private Date birthday;
        private User user;
    
        public Long getId() { 
            return id;
        }
    
        public void setId(Long id) { 
            this.id = id;
        }
    
        public String getName() { 
            return name;
        }
    
        public void setName(String name) { 
            this.name = name;
        }
    
        public String getEmail() { 
            return email;
        }
    
        public void setEmail(String email) { 
            this.email = email;
        }
    
        public Date getBirthday() { 
            return birthday;
        }
    
        public void setBirthday(Date birthday) { 
            this.birthday = birthday;
        }
    
        public User getUser() { 
            return user;
        }
    
        public void setUser(User user) { 
            this.user = user;
        }
    
        public Person(Long id, String name, String email, Date birthday, User user) { 
            this.id = id;
            this.name = name;
            this.email = email;
            this.birthday = birthday;
            this.user = user;
        }
    
        public Person() { 
        }
    }

PersonDTO

package com.bxoon.mapstruct;
    
    
    import java.util.Date;
    
    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;
    
        public Long getId() { 
            return id;
        }
    
        public void setId(Long id) { 
            this.id = id;
        }
    
        public String getName() { 
            return name;
        }
    
        public void setName(String name) { 
            this.name = name;
        }
    
        public Integer getAge() { 
            return age;
        }
    
        public void setAge(Integer age) { 
            this.age = age;
        }
    
        public String getEmail() { 
            return email;
        }
    
        public void setEmail(String email) { 
            this.email = email;
        }
    
        public Date getBirth() { 
            return birth;
        }
    
        public void setBirth(Date birth) { 
            this.birth = birth;
        }
    
        public String getBirthDateFormat() { 
            return birthDateFormat;
        }
    
        public void setBirthDateFormat(String birthDateFormat) { 
            this.birthDateFormat = birthDateFormat;
        }
    
        public String getBirthExpressionFormat() { 
            return birthExpressionFormat;
        }
    
        public void setBirthExpressionFormat(String birthExpressionFormat) { 
            this.birthExpressionFormat = birthExpressionFormat;
        }
    
        public PersonDTO(Long id, String name, Integer age, String email, Date birth, String birthDateFormat, String birthExpressionFormat) { 
            this.id = id;
            this.name = name;
            this.age = age;
            this.email = email;
            this.birth = birth;
            this.birthDateFormat = birthDateFormat;
            this.birthExpressionFormat = birthExpressionFormat;
        }
    
        public PersonDTO() { 
        }
    }

public class User { 
        private Integer age;
    
        public Integer getAge() { 
            return age;
        }
    
        public void setAge(Integer age) { 
            this.age = age;
        }
    
        public User(Integer age) { 
            this.age = age;
        }
    
        public User() { 
        }
    }

PersonConverter

package com.bxoon.mapstruct;
    
    import org.mapstruct.Mapper;
    import org.mapstruct.Mapping;
    import org.mapstruct.Mappings;
    import org.mapstruct.factory.Mappers;
    
    import java.util.List;
    
    @Mapper
    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(org.apache.commons.lang3.time.DateFormatUtils.format(person.getBirthday(),\"yyyy-MM-dd HH:mm:ss\"))"),
            @Mapping(source = "user.age", target = "age"),
            @Mapping(target = "email", ignore = true)
        })
        PersonDTO domain2dto(Person person);
    
        List<PersonDTO> domain2dto(List<Person> people);
    }

写一个测试类使用

package com.bxoon.shardingspheredemo;
    
    import com.bxoon.mapstruct.Person;
    import com.bxoon.mapstruct.PersonConverter;
    import com.bxoon.mapstruct.PersonDTO;
    import com.bxoon.mapstruct.User;
    import org.apache.commons.lang3.time.DateFormatUtils;
    import org.junit.jupiter.api.Test;
    
    import java.util.ArrayList;
    import java.util.Date;
    import java.util.List;
    
    import static org.junit.jupiter.api.Assertions.assertEquals;
    import static org.junit.jupiter.api.Assertions.assertNotNull;
    
    public class PersonConverterTest { 
        @Test
        public void test() { 
            Person person = new Person(1L,"zhige","zhige.me@gmail.com",new Date(),new User(1));
            PersonDTO personDTO = PersonConverter.INSTANCE.domain2dto(person);
            assertNotNull(personDTO);
            assertEquals(personDTO.getId(), person.getId());
            assertEquals(personDTO.getName(), person.getName());
            assertEquals(personDTO.getBirth(), person.getBirthday());
            String format = DateFormatUtils.format(personDTO.getBirth(), "yyyy-MM-dd HH:mm:ss");
            assertEquals(personDTO.getBirthDateFormat(),format);
            assertEquals(personDTO.getBirthExpressionFormat(),format);
    
            List<Person> people = new ArrayList<>();
            people.add(person);
            List<PersonDTO> personDTOs = PersonConverter.INSTANCE.domain2dto(people);
            assertNotNull(personDTOs);
    
        }
    }

MapStruct还有很多种用法，比如可以把多个对象聚合转为一个对象，比如联合springboot的一起使用，详情见  
https://www.cnblogs.com/jpfss/p/10898385.html

# 参考 #

https://www.cnblogs.com/jpfss/p/10898385.html  
https://www.cnblogs.com/hollischuang/p/13469173.html

[20210312152710383.png]: /images/20221023/a47b59448b284af5995750661a7e899b.png
[.]: /images/20221023/294554dae7d84ff2936003fab8543f3e.png