老鐵們是不是經常為寫一些實體轉換的原始代碼感到頭疼，尤其是實體字段特别多的時候。介紹一個開源項目 mapstruct ，可以輕松優雅的進行轉換，簡化你的代碼。當然有的人喜歡寫get set，或者用BeanUtils 進行複制，代碼隻是工具，本文隻是提供一種思路。
先貼下官網位址吧：https://mapstruct.org/
廢話不多說，上代碼：
pom 配置：
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<maven.compiler.source>1.8</maven.compiler.source>
<maven.compiler.target>1.8</maven.compiler.target>
<org.mapstruct.version>1.4.1.Final</org.mapstruct.version>
<org.projectlombok.version>1.18.12</org.projectlombok.version>
</properties>
<dependencies>
<dependency>
<groupId>org.mapstruct</groupId>
<artifactId>mapstruct</artifactId>
<version>${org.mapstruct.version}</version>
</dependency>
<!-- lombok dependencies should not end up on classpath -->
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>${org.projectlombok.version}</version>
<scope>provided</scope>
</dependency>
<!-- idea 2018.1.1 之前的版本需要添加下面的配置，後期的版本就不需要了，可以注釋掉，
我自己用的2019.3 -->
<dependency>
<groupId>org.mapstruct</groupId>
<artifactId>mapstruct-processor</artifactId>
<version>${org.mapstruct.version}</version>
<scope>provided</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.8.1</version>
<configuration>
<source>1.8</source>
<target>1.8</target>
<annotationProcessorPaths>
<path>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>${org.projectlombok.version}</version>
</path>
<path>
<groupId>org.mapstruct</groupId>
<artifactId>mapstruct-processor</artifactId>
<version>${org.mapstruct.version}</version>
</path>
</annotationProcessorPaths>
</configuration>
</plugin>
</plugins>
</build>
關于lombok和mapstruct的版本相容問題多說幾句，maven插件要使用3.6.0版本以上、lombok使用1.16.16版本以上，另外編譯的lombok mapstruct的插件不要忘了加上。否則會出現下面的錯誤：No property named "aaa" exists in source parameter(s). Did you mean "null"?
這種異常就是lombok編譯異常導緻缺少get setter方法造成的。還有就是缺少構造函數也會抛異常。
@Data
@Builder
@AllArgsConstructor
@NoArgsConstructor
public class Student {
private String name;
private int age;
private GenderEnum gender;
private Double height;
private Date birthday;
}
public enum GenderEnum {
Male("1", "男"),
Female("0", "女");
private String code;
private String name;
public String getCode() {
return this.code;
}
public String getName() {
return this.name;
}
GenderEnum(String code, String name) {
this.code = code;
this.name = name;
}
}
@Data
@Builder
@AllArgsConstructor
@NoArgsConstructor
public class StudentVO {
private String name;
private int age;
private String gender;
private Double height;
private String birthday;
}
@Mapper
public interface StudentMapper {
StudentMapper INSTANCE = Mappers.getMapper(StudentMapper.class);
@Mapping(source = "gender.name", target = "gender")
@Mapping(source = "birthday", target = "birthday", dateFormat = "yyyy-MM-dd HH:mm:ss")
StudentVO student2StudentVO(Student student);
}
實體類是開發過程少不了的，就算是用工具生成肯定也是要有的，需要手寫的部分就是這個Mapper的接口，編譯完成後會自動生成相應的實作類
然後就可以直接用mapper進行實體的轉換了
public class Test {
public static void main(String[] args) {
Student student = Student.builder().name("小明").age(6).gender(GenderEnum.Male).height(121.1).birthday(new Date()).build();
System.out.println(student);
//這行代碼便是實際要用的代碼
StudentVO studentVO = StudentMapper.INSTANCE.student2StudentVO(student);
System.out.println(studentVO);
}
}
mapper可以進行字段映射，改變字段類型，指定格式化的方式，包括一些日期的預設處理。
可以手動指定格式化的方法：
@Mapper
public interface StudentMapper {
StudentMapper INSTANCE = Mappers.getMapper(StudentMapper.class);
@Mapping(source = "gender", target = "gender")
@Mapping(source = "birthday", target = "birthday", dateFormat = "yyyy-MM-dd HH:mm:ss")
StudentVO student2StudentVO(Student student);
default String getGenderName(GenderEnum gender) {
return gender.getName();
}
}
上面隻是最簡單的實體映射處理，下面介紹一些進階用法
1.List 轉換
@Mapper
public interface StudentMapper {
StudentMapper INSTANCE = Mappers.getMapper(StudentMapper.class);
@Mapping(source = "gender.name", target = "gender")
@Mapping(source = "birthday", target = "birthday", dateFormat = "yyyy-MM-dd HH:mm:ss")
StudentVO student2StudentVO(Student student);
List<StudentVO> students2StudentVOs(List<Student> studentList);
}
public static void main(String[] args) {
Student student = Student.builder().name("小明").age(6).gender(GenderEnum.Male).height(121.1).birthday(new Date()).build();
List<Student> list = new ArrayList<>();
list.add(student);
List<StudentVO> result = StudentMapper.INSTANCE.students2StudentVOs(list);
System.out.println(result);
}
@Data
@Builder
@AllArgsConstructor
@NoArgsConstructor
public class Student {
private String name;
private int age;
private GenderEnum gender;
private Double height;
private Date birthday;
}
@Data
@AllArgsConstructor
@Builder
@NoArgsConstructor
public class Course {
private String courseName;
private int sortNo;
private long id;
}
@Data
@Builder
@AllArgsConstructor
@NoArgsConstructor
public class StudentVO {
private String name;
private int age;
private String gender;
private Double height;
private String birthday;
private String course;
}
@Mapper
public interface StudentMapper {
StudentMapper INSTANCE = Mappers.getMapper(StudentMapper.class);
@Mapping(source = "student.gender.name", target = "gender")
@Mapping(source = "student.birthday", target = "birthday", dateFormat = "yyyy-MM-dd HH:mm:ss")
@Mapping(source = "course.courseName", target = "course")
StudentVO studentAndCourse2StudentVO(Student student, Course course);
}
public class Test {
public static void main(String[] args) {
Student student = Student.builder().name("小明").age(6).gender(GenderEnum.Male).height(121.1).birthday(new Date()).build();
Course course = Course.builder().id(1L).courseName("國文").build();
StudentVO studentVO = StudentMapper.INSTANCE.studentAndCourse2StudentVO(student, course);
System.out.println(studentVO);
}
}
@Mapper
public interface StudentMapper {
StudentMapper INSTANCE = Mappers.getMapper(StudentMapper.class);
@Mapping(source = "student.gender.name", target = "gender")
@Mapping(source = "student.birthday", target = "birthday", dateFormat = "yyyy-MM-dd HH:mm:ss")
@Mapping(source = "course.courseName", target = "course")
@Mapping(target = "name", source = "student.name", defaultValue = "張三")
StudentVO studentAndCourse2StudentVO(Student student, Course course);
}