老铁们是不是经常为写一些实体转换的原始代码感到头疼,尤其是实体字段特别多的时候。介绍一个开源项目 mapstruct ,可以轻松优雅的进行转换,简化你的代码。当然有的人喜欢写get set,或者用BeanUtils 进行复制,代码只是工具,本文只是提供一种思路。
先贴下官网地址吧:https://mapstruct.org/
废话不多说,上代码:
pom 配置:
properties
project.build.sourceEncodingUTF-8/project.build.sourceEncoding
maven.compiler.source1.8/maven.compiler.source
maven.compiler.target1.8/maven.compiler.target
org.mapstruct.version1.4.1.Final/org.mapstruct.version
org.projectlombok.version1.18.12/org.projectlombok.version
/properties
dependencies
dependency
groupIdorg.mapstruct/groupId
artifactIdmapstruct/artifactId
version${org.mapstruct.version}/version
/dependency
!-- lombok dependencies should not end up on classpath --
dependency
groupIdorg.projectlombok/groupId
artifactIdlombok/artifactId
version${org.projectlombok.version}/version
scopeprovided/scope
/dependency
!-- idea 2018.1.1 之前的版本需要添加下面的配置,后期的版本就不需要了,可以注释掉,
我自己用的2019.3 --
dependency
groupIdorg.mapstruct/groupId
artifactIdmapstruct-processor/artifactId
version${org.mapstruct.version}/version
scopeprovided/scope
/dependency
/dependencies
build
plugins
plugin
groupIdorg.apache.maven.plugins/groupId
artifactIdmaven-compiler-plugin/artifactId
version3.8.1/version
configuration
source1.8/source
target1.8/target
annotationProcessorPaths
path
groupIdorg.projectlombok/groupId
artifactIdlombok/artifactId
version${org.projectlombok.version}/version
/path
path
groupIdorg.mapstruct/groupId
artifactIdmapstruct-processor/artifactId
version${org.mapstruct.version}/version
/path
/annotationProcessorPaths
/configuration
/plugin
/plugins
/build
关于lombok和mapstruct的版本兼容问题多说几句,maven插件要使用3.6.0版本以上、lombok使用1.16.16版本以上,另外编译的lombok mapstruct的插件不要忘了加上。否则会出现下面的错误:No property named “aaa” exists in source parameter(s). Did you mean “null”?
这种异常就是lombok编译异常导致缺少get setter方法造成的。还有就是缺少构造函数也会抛异常。
@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);
}
实体类是开发过程少不了的,就算是用工具生成肯定也是要有的,需要手写的部分就是这个Mapper的接口,编译完成后会自动生成相应的实现类
然后就可以直接用mapper进行实体的转换了
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);
//这行代码便是实际要用的代码
StudentVO studentVO = StudentMapper.INSTANCE.student2StudentVO(student);
System.out.println(studentVO);
}
}
mapper可以进行字段映射,改变字段类型,指定格式化的方式,包括一些日期的默认处理。
可以手动指定格式化的方法:
@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();
}
}
上面只是最简单的实体映射处理,下面介绍一些高级用法
1.List 转换
属性映射基于上面的mapping配置
@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);
ListStudentVO students2StudentVOs(ListStudent 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();
ListStudent list = new ArrayList();
list.add(student);
ListStudentVO result = StudentMapper.INSTANCE.students2StudentVOs(list);
System.out.println(result);
}
2.多对象转换到一个对象
@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("语文").build();
StudentVO studentVO = StudentMapper.INSTANCE.studentAndCourse2StudentVO(student, course);
System.out.println(studentVO);
}
}
3.默认值
@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 = "张三")
StudentVO studentAndCourse2StudentVO(Student student, Course course);
}
END
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