MapStruct_概念、如何使用、子集和映射、合并、Spring方式、表达式、自定义切面处理

①. 什么是MapStruct？

• ①. MapStruct是一款基于Java注解的对象属性映射工具,使用的时候我们只要在接口中定义好对象属性映射规则,它就能自动生成映射实现类,不使用反射,性能优秀,能实现各种复杂映射

• ②. 在平时CRUD的工作中,经常需要做PO、VO、DTO之间的转换。简单的对象转换,使用BeanUtils基本上是够了,但是复杂的转换,如果使用它的话又得写一堆Getter、Setter方法了。BeanUtils 就是一个大老粗,只能同属性映射,或者在属性相同的情况下,允许被映射的对象属性少；但当遇到被映射的属性数据类型被修改或者被映射的字段名被修改,则会导致映射失败

• ③. IDEA下载mapstruct support插件
  

②. 如何使用MapStruct?

• ①. 引入MapStruct依赖

    <properties>
        <lombok.version>1.18.12</lombok.version>
        <mapstruct.version>1.4.2.Final</mapstruct.version>
    </properties>
	<!--MapStruct相关依赖-->
	<dependency>
		<groupId>org.mapstruct</groupId>
		<artifactId>mapstruct</artifactId>
		<version>${mapstruct.version}</version>
	</dependency>
	<dependency>
		<groupId>org.mapstruct</groupId>
		<artifactId>mapstruct-processor</artifactId>
		<version>${mapstruct.version}</version>
		<scope>compile</scope>
	</dependency>
		
    <!--需要加上下面这个插件,不然会报错ClassNotFoundException-->
    <build>
        <plugins>
            <!-- MapStruct 编译器插件 -->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                    <annotationProcessorPaths>
                        <path>
                            <groupId>org.mapstruct</groupId>
                            <artifactId>mapstruct-processor</artifactId>
                            <version>1.4.2.Final</version>
                        </path>
                    </annotationProcessorPaths>
                </configuration>
            </plugin>
        </plugins>
    </build>

• ②. 创建我们所需要的案例实体类

@Data
@NoArgsConstructor
@AllArgsConstructor
@Accessors(chain = true)
public class User {
    private Integer id ;//用户id
    private String userName;//用户名
    private String password; //密码
    private Date birthday;//生日
    private String tel;//电话号码
    private String email; //邮箱
    private String idCardNo;//身份证号
    private String icon; //头像
    private Integer gender;//性别
}

@Data
@NoArgsConstructor
@AllArgsConstructor
@Accessors(chain = true)
@EqualsAndHashCode(callSuper = false)
public class UserVo {
    private Long id ;//用户id
    private String userName;//用户名
    private String password; //密码
	// 与User对象不同的类型
    private String birthday;//生日
    //与User不同的名称
    private String telNumber;//电话号码
    private String email; //邮箱
    private String idCardNo;//身份证号
    private String icon; //头像
    private Integer gender;//性别
}

• ③. 创建映射接口(目的:实现同名同类型属性、不同名称属性、不同类型属性的映射)

/**
 * unmappedTargetPolicy:
 * 目标属性不存在时的处理策略,可选值有:IGNORE默认值、WARN和ERROR。
 * IGNORE默认值:忽略未映射的源属性
 * WARN:任何未映射的源属性都将在生成时引起警告,基于javax.tools.Diagnostic.Kind.WARNING的警告。
 * ERROR:任何未映射的源属性都将导致映射代码生成失败。
 *
 */
@Mapper(unmappedTargetPolicy = ReportingPolicy.IGNORE)
public interface UserMapper {
    UserMapper INSTANCE = Mappers.getMapper(UserMapper.class);

    @Mapping(source = "tel",target = "telNumber")
    @Mapping(source = "birthday",target = "birthday",dateFormat = "yyyy-MM-dd")
    UserVo convertToVo(User user);
}

• ④. 案例演示

@RestController
@RequestMapping("/testController")
@Slf4j
public class TestController {

    @GetMapping("/mapStructToVo")
    public String mapStructToVo() {
        User user = new User();
        user.setId(1).setEmail("84519548@qq.com").setUserName("tang").setBirthday(new Date()).setTel("18774149799");
        UserVo userVo = UserMapper.INSTANCE.convertToVo(user);
        // {"birthday":"2023-10-07","email":"84519548@qq.com","id":1,"telNumber":"18774149799","userName":"tang"}
        System.out.println(JSON.toJSONString(userVo));
        return JSON.toJSONString(userVo);
    }
}

③. 子集和映射

• ①. MapStruct对于对象中包含子对象也需要转换的情况也是有所支持的

• ②. 有一个订单PO对象Order,嵌套有User和Product对象

@Data
@EqualsAndHashCode(callSuper = false)
public class Order {
    private Long id;
    private String orderNo;//订单号
    private Date createTime;
    private String receiverAddress; //收货地址
    private User user;//订单所属的用户
    private List<Product> productList; //商品集合
}
@Data
@Accessors(chain = true)
@EqualsAndHashCode(callSuper = false)
public class Product {
    private Long id;
    private String productSn;
    private String name;
    private String subTitle;
    private String brandName;
    private BigDecimal price;
    private Integer count;//商品数量
    private Date createTime;
}

• ③. 我们需要转换为OrderDo对象,OrderDo中包含UserVo和ProductVo两个子对象同样需要转换；

@Data
@EqualsAndHashCode(callSuper = false)
public class OrderVo {
    private Long id;
    private String orderNo; //订单号
    private Date createTime;
    private String receiverAddress; //收货地址
    //子对象映射Dto
    private UserVo userVo;//订单所属的用户
    //子对象数组映射Dto
    private List<ProductVo> productVoList; //商品集合
}

@Data
@EqualsAndHashCode(callSuper = false)
public class ProductVo {
    //使用常量
    private Long id;
    //使用表达式生成属性
    private String productSn;
    private String name;
    private String subTitle;
    private String brandName;
    private BigDecimal price;
    //使用默认值
    private Integer number;//商品数量
    private Date createTime;
}

• ④. 使用uses将子对象的转换Mapper注入进来,然后通过@Mapping设置好属性映射规则即可

@Mapper(uses = {UserMapper.class,ProductMapper.class})
public interface OrderMapper {
    OrderMapper INSTANCE = Mappers.getMapper(OrderMapper.class);

    @Mapping(source = "user",target = "UserVo")
    @Mapping(source = "productList",target = "productVoList")
    OrderVo convertToVo(Order order);
}

@Mapper(imports = {UUID.class})
public interface ProductMapper {
    ProductMapper INSTANCE = Mappers.getMapper(ProductMapper.class);

    @Mapping(target = "id",constant = "-1L")
    @Mapping(source = "count",target = "number",defaultValue = "1")
    @Mapping(target = "productSn",expression = "java(UUID.randomUUID().toString())")
    ProductVo convertToVo(Product product);
}

• ⑤. 直接通过Mapper中的INSTANCE实例调用转换方法toDto；

    @GetMapping("/mapStructToSubVo")
    public String  mapStructToSubVo() {
        //创建一个user对象
        User user = new User();
        user.setId(1).setEmail("845195485@qq.com").setUserName("tang")
                .setBirthday(new Date()).setTel("18774149799");
        //创建productList
        List<Product> productList = new ArrayList<>();
        productList.add(new Product().setCount(3).setName("test-nameA"));
        productList.add(new Product().setCount(7).setName("test-nameB"));
        Order order = new Order();
        order.setUser(user).setProductList(productList);
        OrderVo orderVo = OrderMapper.INSTANCE.convertToVo(order);
        // {"productVoList":[{"id":-1,"name":"test-nameA","number":3,"productSn":"d7cacdd0-4a13-46b1-a76b-fba7607d68ea"},{"id":-1,"name":"test-nameB","number":7,"productSn":"18f7c91e-c5f1-4bb6-8ae3-6e1e5847f03c"}],"userVo":{"birthday":"2023-10-12","email":"845195485@qq.com","id":1,"telNumber":"18774149799","userName":"tang"}}
        System.out.println(JSON.toJSONString(orderVo));
        return JSON.toJSONString(orderVo);
    }

④. 合并映射

• ①. MapStruct支持把多个对象属性映射到一个对象中去

• ②. 把User和Order的部分属性映射到UserOrderDto中去

@Data
public class UserOrderVo {
    private Long id ;//用户id
    private String userName;//用户名
    private String password; //密码
    //与PO类型不同的属性
    private String birthday;//生日
    //与PO名称不同的属性
    private String telNumber;//电话号码
    private String email;
    private String idCardNo;//身份证号
    private String icon; //头像
    private Integer gender;//性别
    private String orderNo; //订单号
    private String receiverAddress; //用户收货地址
}

• ③. 在Mapper中添加toUserOrderVo方法,这里需要注意的是由于参数中具有两个属性,需要通过参数名称.属性的名称来指定source来防止冲突这两个参数中都有id属性

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

    @Mapping(source = "user.tel",target = "telNumber")
    @Mapping(source = "user.birthday",target = "birthday",dateFormat = "yyyy-MM-dd")
    @Mapping(source = "user.id",target = "id")
    @Mapping(source = "order.orderNo", target = "orderNo")
    @Mapping(source = "order.receiverAddress", target = "receiverAddress")
    UserOrderVo toUserOrderVo(User user, Order order); 
}

• ④. 测试

    @ApiOperation(value = "组合映射")
    @GetMapping("/compositeMapping")
    public String compositeMapping() {
        //新建一个user对象
        User user = new User();
        user.setBirthday(new Date()).setTel("110");
        //新建一个Order对象
        Order order = new Order();
        order.setReceiverAddress("湖南长沙测试").setOrderNo("123456789");
        // {"birthday":"2023-10-12","orderNo":"123456789","receiverAddress":"湖南长沙测试","telNumber":"110"}
        UserOrderVo userOrderVo = UserMapper.INSTANCE.toUserOrderVo(user,order);
        System.out.println(JSON.toJSONString(userOrderVo));
        return JSON.toJSONString(userOrderVo);
    }

⑤. Spring依赖注入

• ①. 想要使用依赖注入,我们只要将@Mapper注解的componentModel参数设置为spring即可,这样在生成接口实现类时,MapperStruct会为其添加@Component注解

@Mapper(componentModel = "spring")
public interface UserSpringMapper {


    @Mappings({
            @Mapping(source = "tel", target = "telNumber"),
            @Mapping(source = "birthday", target = "birthday", dateFormat = "yyyy-MM-dd")
    })
    UserVo convertToVo(User user);
}

• ②. 测试数据

    @Autowired
    private UserSpringMapper userMapper;
    @GetMapping("/mapStructToVoSpring")
    public String mapStructToVoSpring() {
        User user = new User();
        // {"birthday":"2023-10-12","email":"845195485@qq.com","id":1,"telNumber":"18774149733","userName":"tang"}
        user.setId(1).setEmail("845195485@qq.com").setUserName("tang").setBirthday(new Date()).setTel("18774149733");
        UserVo userVo = userMapper.convertToVo(user);
        System.out.println(JSON.toJSONString(userVo));
        return JSON.toJSONString(userVo);
    }

⑥. 常量、默认值和表达式

• ①. 使用MapStruct映射属性时,我们可以设置属性为常量或者默认值,也可以通过Java中的方法编写表达式来自动生成属性

@Data
@Accessors(chain = true)
public class Product {
    private Long id;
    private String productSn;
    private String name;
    private String subTitle;
    private String brandName;
    private BigDecimal price;
    private Integer count;//商品数量
    private Date createTime;
}

• ②. Product转换为ProductVo对象,id属性设置为常量,count设置默认值为1,productSn设置为UUID生成

@Data
public class ProductVo {
    //使用常量
    private Long id;
    //使用表达式生成属性
    private String productSn;
    private String name;
    private String subTitle;
    private String brandName;
    private BigDecimal price;
    //使用默认值
    private Integer number;//商品数量
    private Date createTime;
}

• ③. 创建ProductMapper接口,通过@Mapping注解中的constant、defaultValue、expression设置好映射规则；

@Mapper(imports = {UUID.class})
public interface ProductMapper {
    ProductMapper INSTANCE = Mappers.getMapper(ProductMapper.class);

    @Mapping(target = "id",constant = "-1L")  //给转换后的productVo的id字段设置为常量-1
    @Mapping(source = "count",target = "number",defaultValue = "1")
    @Mapping(target = "productSn",expression = "java(UUID.randomUUID().toString())")
    ProductVo convertToVo(Product product);
}

• ④. 测试数据

    @GetMapping("/defaultMapping")
    public Result defaultMapping() {
        Product product = new Product();
        product.setId(200L);
        product.setCount(null);
        ProductVo productVo = ProductMapper.INSTANCE.convertToVo(product);
        System.out.println(JSON.toJSONString(productVo));
        return Result.success(productVo);
    }

⑦. 自定义切面处理

• ①. MapStruct也支持在映射前后做一些自定义操作,类似Spring的AOP中的切面

• ②. 此时我们需要创建自定义处理方法,创建一个抽象类ProductRoundMapper,通过@BeforeMapping注解自定义映射前操作,通过@AfterMapping注解自定义映射后操作

@Mapper(imports = {UUID.class},unmappedTargetPolicy = ReportingPolicy.IGNORE)
public abstract class ProductRoundMapper {
    public static ProductRoundMapper INSTANCE = Mappers.getMapper(ProductRoundMapper.class);

    @Mappings({
            @Mapping(target = "id",constant = "-1L"),
            @Mapping(source = "count",target = "number",defaultValue = "1"),
            @Mapping(target = "productSn",expression = "java(UUID.randomUUID().toString())")
    })
    public abstract ProductVo convertToVo(Product product);

    @BeforeMapping
    public void beforeMapping(Product product){
        //映射前当price<0时设置为0
        if(product.getPrice().compareTo(BigDecimal.ZERO)<0){
            product.setPrice(BigDecimal.ZERO);
        }
    }

    @AfterMapping
    public void afterMapping(@MappingTarget ProductVo productVo){
        //映射后设置当前时间为createTime
        productVo.setCreateTime(new Date());
    }
}

• ③. 测试

    @GetMapping("/aspectMapping")
    public String defaultMapping() {
        Product product = new Product();
        product.setId(100L);
        product.setCount(null);
        product.setPrice(new BigDecimal(-100) );
        ProductVo productVo = ProductRoundMapper.INSTANCE.convertToVo(product);
        // {"createTime":1697113274023,"id":-1,"number":1,"price":0,"productSn":"fe154c52-8808-40e1-b0a6-68b5e6437ea5"}
        System.out.println(JSON.toJSONString(productVo));
        return JSON.toJSONString(productVo);
    }

• ④. 如果需要将一个List转为另外一个List,可以使用这种方式

 result  = xxxList.stream()
                    .map(XXX.INSTANCE::convertNew).collect(Collectors.toList());