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  • Java com.fasterxml.jackson.databind.JsonMappingException:无法构造：poja类的实例找不到合适的构造函数

Java com.fasterxml.jackson.databind.JsonMappingException:无法构造：poja类的实例找不到合适的构造函数

java spring

Java com.fasterxml.jackson.databind.JsonMappingException:无法构造：poja类的实例找不到合适的构造函数,java,spring,jackson,jackson-databind,java-ee-8,Java,Spring,Jackson,Jackson Databind,Java Ee 8,这是ApiError的POJO类。我正在尝试将string转换为以下类。我正在将{“message”：“success”，“code”：“403”}字符串传递给convertToObject方法 package com.wrapper.reply; import com.fasterxml.jackson.annotation.JsonIgnoreProperties; import lombok.Builder; import lombok.Getter; import lombok.Requ

这是ApiError的POJO类。我正在尝试将string转换为以下类。我正在将{“message”：“success”，“code”：“403”}字符串传递给convertToObject方法

package com.wrapper.reply;
import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
import lombok.Builder;
import lombok.Getter;
import lombok.RequiredArgsConstructor;
@Getter
@Builder
@RequiredArgsConstructor
@JsonIgnoreProperties(ignoreUnknown = true)
public final class ApiError {
  private final String code;
  private final String message;
}



public static <T> T convertToObject(String body, Class<T> clazz) {
    try {
      ObjectMapper mapper = new ObjectMapper();
      return mapper.readValue(body, clazz);
    } catch (IOException e) {
      log.error(ERRMSG_PARSE_JSON, e);
      throw new BadRequestException(ERRMSG_PARSE_JSON, e);
    }
  }
更新： 默认情况下，Jackson似乎会在创建对象实例后尝试设置值，如果类具有
final
字段，则不可能这样做

因此，我们需要定义一个构造函数并用
@JsonCreator
注释，以告诉Jackson使用构造函数进行反序列化

@Getter
@建筑商
//@所需参数构造函数
@JsonIgnoreProperties（ignoreUnknown=true）
类错误{
私有最终字符串代码；
私有最终字符串消息；
@JsonCreator
公共ApiError（@JsonProperty（“代码”）字符串代码，@JsonProperty（“消息”）字符串消息）{
this.code=代码；
this.message=消息；
}
}
Jackson无法找到实例化
apierro
对象并为其设置值的方法

您需要对
apirerror
类执行以下任何一项更改

  • 用
    @JsonPOJOBuilder（with prefix=“”）注释
  • 添加setter方法（或lombok
    @setter
    ）
  • 添加参数化构造函数（或lombok
    @allargsconstuctor
    ）
    • 缺少默认构造函数或创建者

    @NoArgsConstructor

    这不会解决问题，因为
    APIRROR
    没有设置器。它使用生成器模式。 
    12:58:44.458 [main] ERROR com.JsonUtil - Exception in parsing json string
com.fasterxml.jackson.databind.JsonMappingException: Can not construct instance of com.wrapper.reply.ApiError: no suitable constructor found, can not deserialize from Object value (missing default constructor or creator, or perhaps need to add/enable type information?)
 at [Source: {"message": "success", "code":"403"}; line: 1, column: 2]
    at com.fasterxml.jackson.databind.JsonMappingException.from(JsonMappingException.java:270)
    at com.fasterxml.jackson.databind.DeserializationContext.instantiationException(DeserializationContext.java:1456)
    at com.fasterxml.jackson.databind.DeserializationContext.handleMissingInstantiator(DeserializationContext.java:1012)
    at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeFromObjectUsingNonDefault(BeanDeserializerBase.java:1206)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:314)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:148)
    at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:3814)
    at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2858)
    at com.JsonUtil.convertToObject(JsonUtil.java:62)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:566)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
    at org.mockito.internal.runners.JUnit45AndHigherRunnerImpl.run(JUnit45AndHigherRunnerImpl.java:37)
    at org.mockito.runners.MockitoJUnitRunner.run(MockitoJUnitRunner.java:62)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
    at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33)
    at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:230)
    at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:58)

com.exception.BadRequestException: Exception in parsing json string

    at com.JsonUtil.convertToObject(JsonUtil.java:65)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:566)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
    at org.mockito.internal.runners.JUnit45AndHigherRunnerImpl.run(JUnit45AndHigherRunnerImpl.java:37)
    at org.mockito.runners.MockitoJUnitRunner.run(MockitoJUnitRunner.java:62)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
    at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33)
    at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:230)
    at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:58)
Caused by: com.fasterxml.jackson.databind.JsonMappingException: Can not construct instance of com.wrapper.reply.ApiError: no suitable constructor found, can not deserialize from Object value (missing default constructor or creator, or perhaps need to add/enable type information?)
 at [Source: {"message": "success", "code":"403"}; line: 1, column: 2]
    at com.fasterxml.jackson.databind.JsonMappingException.from(JsonMappingException.java:270)
    at com.fasterxml.jackson.databind.DeserializationContext.instantiationException(DeserializationContext.java:1456)
    at com.fasterxml.jackson.databind.DeserializationContext.handleMissingInstantiator(DeserializationContext.java:1012)
    at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeFromObjectUsingNonDefault(BeanDeserializerBase.java:1206)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:314)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:148)
    at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:3814)
    at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2858)
    at com.JsonUtil.convertToObject(JsonUtil.java:62)
    ... 28 more

Disconnected from the target VM, address: '127.0.0.1:56545', transport: 'socket'

Process finished with exit code 255