Mapstruct使用介绍

一：使用背景

我们在读库之后(po->dto)，返回前端数据(dto->vo)的需要转换函数，这时候我们一般会有以下几种方式

1：手动编写convert函数

2：利用反射工具进行映射(spring的BeanUtils, fastjson的JSON.parseObject)

3：利用工具生成convert函数(Mapstruct)

个人比较偏好Mapstruct，手动写convert函数比较繁琐，而且很多转换的过程中属性名和属性类型都是相同的。

反射工具进行映射的性能无法保证，也可能出现问题(比如fastjson已经被人在社区中提出bug)。

二：使用姿势

实例一(字段完全相同)

1：在pom.xml中引入依赖。

<dependency><groupid>junit</groupid><artifactid>junit</artifactid><version>4.11</version><scope>test</scope>
</dependency>
<plugin><groupid>org.apache.maven.plugins</groupid><artifactid>maven-compiler-plugin</artifactid><version>3.5.1</version><configuration><source>1.8<target>1.8</target><annotationprocessorpaths><path><groupid>org.mapstruct</groupid><artifactid>mapstruct-processor</artifactid><version>1.3.0.Beta2</version></path></annotationprocessorpaths></configuration>
</plugin>

2：编写要转换的两个实体类

package controller;/*** @date: 2019/10/24* @description: SimpleSource*/
public class SimpleSource {private String name;private String description;public String getName() {return name;}public void setName(String name) {this.name = name;}public String getDescription() {return description;}public void setDescription(String description) {this.description = description;}
}

package controller;/*** @date: 2019/10/24* @description: SimpleDestination*/
public class SimpleDestination {private String name;private String description;public String getName() {return name;}public void setName(String name) {this.name = name;}public String getDescription() {return description;}public void setDescription(String description) {this.description = description;}
}

3：编写要映射的Mapper接口

package controller;
import org.mapstruct.Mapper;@Mapper
public interface SimpleSourceDestinationMapper {SimpleDestination sourceToDestination(SimpleSource source);SimpleSource destinationToSource(SimpleDestination destination);
}

4：mvn clean install生成要转换的convert函数(生成的代码在target文件夹下)

5：生成代码

package controller;import javax.annotation.Generated;public class SimpleSourceDestinationMapperImpl implements SimpleSourceDestinationMapper {@Overridepublic SimpleDestination sourceToDestination(SimpleSource source) {if ( source == null ) {return null;}SimpleDestination simpleDestination = new SimpleDestination();simpleDestination.setName( source.getName() );simpleDestination.setDescription( source.getDescription() );return simpleDestination;}@Overridepublic SimpleSource destinationToSource(SimpleDestination destination) {if ( destination == null ) {return null;}SimpleSource simpleSource = new SimpleSource();simpleSource.setName( destination.getName() );simpleSource.setDescription( destination.getDescription() );return simpleSource;}
}

实例二(字段有差异)

1：编写要转换的两个实体类

package controller;/*** @date: 2019/10/24* @description: Person实体类*/
public class Person {private String name;private String sex;private Integer age;private String tall;public String getName() {return name;}public void setName(String name) {this.name = name;}public String getSex() {return sex;}public void setSex(String sex) {this.sex = sex;}public Integer getAge() {return age;}public void setAge(Integer age) {this.age = age;}public String getTall() {return tall;}public void setTall(String tall) {this.tall = tall;}
}

package controller;/*** @date: 2019/10/24* @description: 学生实体类*/
public class Student {private String name;private String sex;private Integer age;private Long height;private Integer rank;public String getName() {return name;}public void setName(String name) {this.name = name;}public String getSex() {return sex;}public void setSex(String sex) {this.sex = sex;}public Integer getAge() {return age;}public void setAge(Integer age) {this.age = age;}public Long getHeight() {return height;}public void setHeight(Long height) {this.height = height;}public Integer getRank() {return rank;}public void setRank(Integer rank) {this.rank = rank;}
}

2：编写要映射的Mapper接口()

package controller;import org.mapstruct.Mapper;
import org.mapstruct.Mapping;
import org.mapstruct.Mappings;
@Mapper
public interface PersonMapper
{@Mappings({@Mapping(source = "tall", target = "height"),})Student personToStudent(Person person);
}

3：生成的Mapper实现类的位置

4：生成的代码

package controller;import javax.annotation.Generated;public class PersonMapperImpl implements PersonMapper {@Overridepublic Student personToStudent(Person person) {if ( person == null ) {return null;}Student student = new Student();if ( person.getTall() != null ) {student.setHeight( Long.parseLong( person.getTall() ) );}student.setName( person.getName() );student.setSex( person.getSex() );student.setAge( person.getAge() );return student;}
}

三：注意事项

1：要映射的源实体类和目的实体类要写setter

2：要映射的源实体类和目的实体类不要写全参数的构造函数(否则未自动映射的字段并且未处理的字段会有问题)。