MapStruct,对象装载结构工具

Posted 2021-08-26 阿昌喜欢吃黄桃

MapStruct工具使用

工具名为MapStruct，用于对象与对象之间的互相转换，避免每一个字段都 get/set 造成麻烦。

MapStruct官网地址： http://mapstruct.org/

如下的演示使用到了Lombok工具，如果不熟悉的请自行了解，这里就不说了。

一、引包

<!--mapstruct-->
<dependency>
    <groupId>org.mapstruct</groupId>
    <!-- jdk8以下就使用mapstruct -->
    <artifactId>mapstruct-jdk8</artifactId>
    <version>1.2.0.Final</version>
</dependency>
<dependency>
    <groupId>org.mapstruct</groupId>
    <artifactId>mapstruct-processor</artifactId>
    <version>1.2.0.Final</version>
</dependency>

---

二、demo

1、当对象属性相同时

• source源对象

@Data
@NoArgsConstructor
@AllArgsConstructor
@Builder
public class Person{
    private String name;
    private Integer age;
}

• target目标对象

@Data
@NoArgsConstructor
@AllArgsConstructor
public class PersonVo{
    private String name;
    private Integer age;
}

• MapStructMapper接口

import org.mapstruct.Mapper;

@Mapper
public interface PersonMapMapper {
    PersonMapMapper INSTANCE = Mappers.getMapper(PersonMapMapper.class);

    PersonVo toPersonVo(Person person);
}

• 他会自动在target/classes下生成对应MapStructMapper接口的实现类

public class PersonMapMapperImpl implements PersonMapMapper {
    public PersonMapMapperImpl() {
    }

    public PersonVo toPersonVo(Person person) {
        if (person == null) {
            return null;
        } else {
            PersonVo personVo = new PersonVo();
            personVo.setName(person.getName());
            personVo.setAge(person.getAge());
            return personVo;
        }
    }
}

• 测试

public class test {
    public static void main(String[] args) {
        Person person = Person.builder().age(1).name("阿昌").build();
        PersonVo personVo = PersonMapMapper.INSTANCE.toPersonVo(person);
        System.out.println(personVo);
    }
}

---

2、当对象属性不同时

• source源对象

@Data
@NoArgsConstructor
@AllArgsConstructor
@Builder
public class Person{
    private String name;
    private Integer age;
}

• target目标对象

@Data
@NoArgsConstructor
@AllArgsConstructor
public class PersonVo{
    private String name123;
    private Integer age123;
}

• MapStructMapper接口

import org.mapstruct.Mapper;
import org.mapstruct.Mapping;
import org.mapstruct.Mappings;
import org.mapstruct.factory.Mappers;

@Mapper
public interface PersonMapMapper {
    PersonMapMapper INSTANCE = Mappers.getMapper(PersonMapMapper.class);

    @Mappings({
            @Mapping(source = "name",target = "name123"),
            @Mapping(source = "age",target = "age123")
    })
    PersonVo toPersonVo(Person person);
}

• 他会自动在target/classes下生成对应MapStructMapper接口的实现类

package com.achang.fmService.testMapStruct;

public class PersonMapMapperImpl implements PersonMapMapper {
    public PersonMapMapperImpl() {
    }

    public PersonVo toPersonVo(Person person) {
        if (person == null) {
            return null;
        } else {
            PersonVo personVo = new PersonVo();
            personVo.setName123(person.getName());
            personVo.setAge123(person.getAge());
            return personVo;
        }
    }
}

• 测试

public class test {
    public static void main(String[] args) {
        Person person = Person.builder().age(1).name("阿昌").build();
        PersonVo personVo = PersonMapMapper.INSTANCE.toPersonVo(person);
        System.out.println(personVo);
    }
}

---

3、如何结合springIoc容器？

添加==@Mapper(componentModel = “spring”)==

@Mapper(componentModel = "spring")//通过componentModel属性来指定环境为spirng
public interface PersonMapMapper {
    PersonMapMapper INSTANCE = Mappers.getMapper(PersonMapMapper.class);

    @Mappings({
            @Mapping(source = "name",target = "name123"),
            @Mapping(source = "age",target = "age123")
    })
    PersonVo toPersonVo(Person person);
}

• 生成的Impl文件

发现自动生成了@Component

@Component //发现出现了@Component
public class PersonMapMapperImpl implements PersonMapMapper {
    public PersonMapMapperImpl() {
    }

    public PersonVo toPersonVo(Person person) {
        if (person == null) {
            return null;
        } else {
            PersonVo personVo = new PersonVo();
            personVo.setName123(person.getName());
            personVo.setAge123(person.getAge());
            return personVo;
        }
    }
}

下次就可以直接通过@Autowired注入使用

// 注入Mapper
@Autowired
private PersonMapMapper mapper;

@GetMapping("/test")
public String test() {
    Person person = new Person("阿昌", 1);
    PersonVo personVo = mapper.toPersonVo(person);
    return personVo.toString();
}

---

4、如果对象里面还有对象的情况，和多参数情况，和传入参数情况

通过Mapping中source属性中指定源对象里面属性的对象，用点来隔开指定

	@Mappings({
            @Mapping(source = "user.id", target = "userId"), // 指定对象里面的属性
            @Mapping(source = "role.name", target = "roleName"), // 指定对象里面的属性
            @Mapping(source = "myRoleDesc", target = "myRoleDesc") //使用参数既可
    })
    UserRoleDto toUserRoleDto(User user, Role role,String myRoleDesc);

---

5、更新对象属性

MapStruct提供了另外一种方式来更新一个对象中的属性。@MappingTarget

    @Mappings({
            @Mapping(source = "id", target = "userId"),
            @Mapping(source = "username", target = "name"),
            @Mapping(source = "role.roleName", target = "roleName")
    })
    void update(User user, @MappingTarget UserRoleDto userRoleDto);

通过@MappingTarget来指定目标类是谁（谁的属性需要被更新）。@Mapping还是用来定义属性对应规则。

上面的演示就是说，从user对象中的id属性，更新到userRoleDto对象中的userId属性

---

6、自定义类型转换

有时候，在对象转换的时候可能会出现这样一个问题，就是源对象中的类型是Boolean类型，而目标对象类型是String类型，这种情况可以通过@Mapper的uses属性来实现：

@Data
@NoArgsConstructor
@AllArgsConstructor
public class Customer {
    private Long id;
    private String name;
    private Boolean isDisable;
}

@Data
public class CustomerDto {
    private Long id;
    private String customerName;
    private String disable;
}

定义转换规则的类：

public class BooleanStrFormat {
    public String toStr(Boolean isDisable) {
        if (isDisable) {
            return "Y";
        } else {
            return "N";
        }
    }
    public Boolean toBoolean(String str) {
        if (str.equals("Y")) {
            return true;
        } else {
            return false;
        }
    }
}

定义Mapper，@Mapper( uses = { BooleanStrFormat.class})，注意，这里的users属性用于引用之前定义的转换规则的类：

@Mapper( uses = { BooleanStrFormat.class})//使用我们自定义的转换类型规则
public interface CustomerMapper {

    CustomerMapper INSTANCES = Mappers.getMapper(CustomerMapper.class);

    @Mappings({
            @Mapping(source = "name", target = "	customerName"),
            @Mapping(source = "isDisable", target = "disable")
    })
    CustomerDto toCustomerDto(Customer customer);
}