ジャクソンを使用してJava例外をシリアライズ

Question

package com.dh.inheritance; 

import com.fasterxml.jackson.annotation.JsonAutoDetect; 
import com.fasterxml.jackson.annotation.JsonTypeInfo; 
import com.fasterxml.jackson.annotation.PropertyAccessor; 
import com.fasterxml.jackson.core.JsonProcessingException; 
import com.fasterxml.jackson.databind.ObjectMapper; 
import com.fasterxml.jackson.databind.SerializationFeature; 


public class Client6{ 

    public static void main(String[] args){ 

     ObjectMapper objectMapper = new ObjectMapper(); 
     objectMapper.enableDefaultTyping(); 
     objectMapper.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL, JsonTypeInfo.As.WRAPPER_OBJECT);   
     objectMapper.setVisibility(PropertyAccessor.SETTER, JsonAutoDetect.Visibility.NONE); 
     objectMapper.setVisibility(PropertyAccessor.GETTER, JsonAutoDetect.Visibility.NONE); 
     objectMapper.setVisibility(PropertyAccessor.FIELD, JsonAutoDetect.Visibility.ANY); 
     objectMapper.setVisibility(PropertyAccessor.IS_GETTER, JsonAutoDetect.Visibility.NONE);   
     objectMapper.configure(SerializationFeature.WRITE_NULL_MAP_VALUES, true); 
     objectMapper.configure(SerializationFeature.FAIL_ON_SELF_REFERENCES, true); 

     try { 

      String test = null; 
      test.length(); 

     } catch (Exception e) { 

      try { 
       String jsonString = objectMapper.writeValueAsString(e); 
       System.out.println(jsonString); 
      } catch (JsonProcessingException e1) { 
       e1.printStackTrace(); 
      } 
     } 
    } 

} 

上記のコードを実行すると、私は例外以下になります。私にこの問題を解決する方法を教えてください。

com.fasterxml.jackson.databind.JsonMappingException: Direct self-reference leading to cycle (through reference chain: java.lang.NullPointerException["cause"]) 
    at com.fasterxml.jackson.databind.JsonMappingException.from(JsonMappingException.java:230) 
    at com.fasterxml.jackson.databind.ser.BeanPropertyWriter._handleSelfReference(BeanPropertyWriter.java:879) 
    at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:666) 
    at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:678) 
    at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeWithType(BeanSerializerBase.java:569) 
    at com.fasterxml.jackson.databind.ser.impl.TypeWrappedSerializer.serialize(TypeWrappedSerializer.java:32) 
    at com.fasterxml.jackson.databind.ser.DefaultSerializerProvider.serializeValue(DefaultSerializerProvider.java:130) 
    at com.fasterxml.jackson.databind.ObjectMapper._configAndWriteValue(ObjectMapper.java:3613) 
    at com.fasterxml.jackson.databind.ObjectMapper.writeValueAsString(ObjectMapper.java:2980) 
    at com.dh.inheritance.Client6.main(Client6.java:33) 

Answer 1

json文字列として書き込むコードの下で動作しています。

objectMapper.registerModule（new MyModule（））;

package com.dh.inheritance; 

import com.fasterxml.jackson.annotation.JsonIdentityInfo; 
import com.fasterxml.jackson.annotation.ObjectIdGenerators; 


public abstract class MixIn { 

    @JsonIdentityInfo(generator=ObjectIdGenerators.StringIdGenerator.class, property="$id") 
    private Throwable cause; 

} 

package com.dh.inheritance; 

import com.fasterxml.jackson.core.Version; 
import com.fasterxml.jackson.databind.module.SimpleModule; 

public class MyModule extends SimpleModule{ 

    public MyModule() { 
     super("test", new Version(2, 7, 2, null)); 
    } 

    @Override 
    public void setupModule(SetupContext context) { 
     context.setMixInAnnotations(Throwable.class, MixIn.class);  
    } 

} 

しかし、jsonからObjectへの読み込みに失敗しました。 出力：

{ "java.lang.NullPointerExceptionが"：{ "detailMessage"：ヌル、 "原因"：{ "java.lang.NullPointerExceptionが"：{ "$のID"： "912da540-bf85-4e5d "StackTrace"：null}} com.fasterxml.jackson "、" stackTrace "：null}}、" stackTrace "：null}}、" stackTrace "：null}}、" detailMessage "：null、"原因 "：" 912da540-bf85-4e5d-869c-acfaebe85bdf " （原因： "cause"、 "stackTrace"、 "detailMessage"]）で指定されていない フィールドが認識されませんでした。 "" "detailMessage"：null、 "cause"：{"java.lang.NullPointerException"：{"$ id"： "912da540-bf85-4e5d-869c-acfaebe85b： {" java.lang.NullPointerException " df "、" detailMessage "：null、" cause "：" 912da540-bf85-4e5d-869c-acfaebe85bdf "、" stackTrace "：null}}、" stackTrace "：null}}; （参照番号チェーン： java.lang.NullPointerException ["$ id"]）） com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException.from（UnrecognizedPropertyException.java:62） at com.fasterxml.jackson.databind.DeserializationContext.reportUnknownProperty（DeserializationContext.java:855） でcom.fasterxml.jackson.databind.deser.std.StdDeserializer.handleUnknownProperty（StdDeserializer.java:1083） com.fasterxmlで.jackson.databind.deser.BeanDeserializerBase.handleUnknownProperty（BeanDeserializerBase.java:1389） でcom.fasterxml.jackson.databind.deser.std.ThrowableDeserializer.deserializeFromObject（ThrowableDeserializer.java:135） でcom.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize（BeanDeserializer.java:133） com.fasterxml.jackson.databind.jsontype.impl.AsWrapperTypeDeserializer._deserialize（AsWrapperTypeDeserializer.java:115） でで で com.fasterxml.jackson.databind.jsontype.impl.AsWrapperTypeDeserializer.deserializeTypedFromObject com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeWithType（BeanDeserializerBase.java:1017）で（AsWrapperTypeDeserializer.java:49） コム.fasterxml.jackson.databind.deser.SettableBeanProperty.deserialize（SettableBeanProperty.java:488） at com.fasterxml.jackson.databind.deser.std.ThrowableDeseri alizer.deserializeFromObject（ThrowableDeserializer.java:104） でcom.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize（BeanDeserializer.java:133） com.fasterxml.jackson.databind.jsontype.impl.AsWrapperTypeDeserializerで。 で_deserialize（AsWrapperTypeDeserializer.java:115） com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeWithTypeでcom.fasterxml.jackson.databind.jsontype.impl.AsWrapperTypeDeserializer.deserializeTypedFromObject（AsWrapperTypeDeserializer.java:49） （ BeanDeserializerBase.java:1017） at com.fasterxml.jackson.databind。 com.fasterxml.jackson.databind.ObjectMapper.readValueでcom.fasterxml.jackson.databind.ObjectMapper._readMapAndClose（ObjectMapper.java:3789） （ でdeser.impl.TypeWrappedDeserializer.deserialize（TypeWrappedDeserializer.java:42） ObjectMapper.java:2779）com.dh.inheritance.Client6.main（Client6.java:45）で