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？
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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
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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
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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
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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());
