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java - “@RequiredArgsConstructor”和“MismatchedInputException：无法构造实例”

问题描述

我有多个 DTO 对象，它们看起来都像这样：

@Getter
@RequiredArgsConstructor
public class SomeDTO {
  private final String someProperty;
}

这些 DTO 对象以各种RestController方法接受：

@RestController
public void InvitationController {

  @PostMapping
  public String create(@RequestBody InvitationCreationDTO invitationCreationDTO) {
    // some logic
    return "ok";
  }

}

Jackson 将 json 反序列化为这些类没有问题，除了以下一个：

@Getter
@RequiredArgsConstructor
public class InvitationCreationDTO {
  private final String emailAddress;
}

当 Jackson 尝试反序列化以下 JSON 时：

{ "emailAddress" : "some@email.com" }

抛出此错误：

Caused by: com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot construct instance of `my.package.InvitationCreationDTO` (although at least one Creator exists): cannot deserialize from Object value (no delegate- or property-based Creator)
 at [Source: (PushbackInputStream); line: 1, column: 2]
    at com.fasterxml.jackson.databind.exc.MismatchedInputException.from(MismatchedInputException.java:63) ~[jackson-databind-2.10.2.jar:2.10.2]
    at com.fasterxml.jackson.databind.DeserializationContext.reportInputMismatch(DeserializationContext.java:1429) ~[jackson-databind-2.10.2.jar:2.10.2]
    at com.fasterxml.jackson.databind.DeserializationContext.handleMissingInstantiator(DeserializationContext.java:1059) ~[jackson-databind-2.10.2.jar:2.10.2]
    at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeFromObjectUsingNonDefault(BeanDeserializerBase.java:1297) ~[jackson-databind-2.10.2.jar:2.10.2]
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:326) ~[jackson-databind-2.10.2.jar:2.10.2]
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:159) ~[jackson-databind-2.10.2.jar:2.10.2]
    at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:4202) ~[jackson-databind-2.10.2.jar:2.10.2]
    at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3258) ~[jackson-databind-2.10.2.jar:2.10.2]
    at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.readJavaType(AbstractJackson2HttpMessageConverter.java:239) ~[spring-web-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    ... 86 common frames omitted

但是，当我自己删除@RequiredArgsConstructor并创建一个时，它可以工作：

@Getter
public class InvitationCreationDTO {
  private final String emailAddress;

  @JsonCreator
  public InvitationCreationDTO(String emailAddress) {
    this.emailAddress = emailAddress;
  }
}

为什么这个类需要这个，但我的其他 DTO 类（具有相同格式）却不需要？

标签： javaspring-mvcjacksonspring-restcontroller

解决方案

尝试添加@NoArgsConstructor到您的InvitationCreationDTO班级

@Getter
@NoArgsConstructor
@RequiredArgsConstructor
public class InvitationCreationDTO {
  private final String emailAddress;
}

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