spring java 后端 MapStruct

文章目录

①. 什么是MapStruct？②. 如何使用MapStruct?③. 子集和映射④. 合并映射⑤. Spring依赖注入⑥. 常量、默认值和表达式⑦. 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

1.18.12

1.4.2.Final

org.mapstruct

mapstruct

${mapstruct.version}

org.mapstruct

mapstruct-processor

${mapstruct.version}

compile

org.apache.maven.plugins

maven-compiler-plugin

1.8

1.8

org.mapstruct

mapstruct-processor

1.4.2.Final

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 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 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 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());

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