Use JsonIgnore for an attribute in an other class

user_12084130 0
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I meet an issue with a class contained in a library that I use.

This issue comes when I want deserialize it.

Indeed, this class has a method names "getCopy" which returns a new instance of himself which contains this same method and call it still a StackOverFlowException on the following cycle :

at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:166)

at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:728)

at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:723)

public class Object {
   ...
   ObjectAttribute objectAttribute;
   ...

   public ObjectAttribute getObjectAttribute(){
      return this.objectAttribute
   }
   ...
}

public class ObjectAttribute{
   ...

   public ObjectAttribute getCopy{
      return copy(this) //return a new instance of himself
   }
   ...
}

Is there a way to ignore the method getCopy() like @JsonIgnoreAttribute("objectProperty.copy")?

stack-overflow json java
5 Answers

For this specific use case, when you have a class in a third party library that you are not able to modify, Jackson provides the Mix-in annotations.

The idea behind this concept is to provide a class that indicates how the serialization of another class should be accomplished.

For instance, consider the following mix-in class definition for your use case:

public abstract class ObjectAttributeMixIn{
   // You need to provide definitions for every property you need
   // to serialize, and the proper constructor if necessary
   ...

   // Ignore the getCopy method
   @JsonIgnore
   public abstract ObjectAttribute getCopy();

   ...
}

You can use the full set of Jackson annotations in the mix-in definitions.

Then, associate the mix-in with the ObjectAttribute class. You can use the instance of ObjectMapper you are using for serialization for this purpose:

objectMapper.addMixInAnnotations(ObjectAttribute.class, ObjectAttributeMixIn.class);

Yon can also register a custom module instead; please, see the relevant documentation.

user_139424480

for ignore method getCopy, just enough rename this method , e.g copy

every method start with get then serialized ,e.g if method name is getSomething then serialized to something: (return value by method))

so if you change method name to copy or copyInstance or every name without start by get then method not serialized

user_129353040

You can override JsonSerializer and do specific logic for class

public class CustomSerializerForC extends JsonSerializer<C> {
   @Override
   public Class<C> handledType() {
       return C.class;
   }
  @Override
   public void serialize(C c, JsonGenerator jsonGenerator, SerializerProvider serializerProvider) throws IOException, JsonProcessingException {
       String upperCase = c.getValue().toUpperCase();
       jsonGenerator.writeString(upperCase);
   }
}

And use Serializer in moudle used in ObjectMapper:

   SimpleModule module = new SimpleModule("MyCustomModule", new Version(1, 0, 0, null));
   module.addSerializer(new CustomSerializerForC());
   ObjectMapper mapper = new ObjectMapper();
   mapper.registerModule(module);
user_72949000

You can register serializer and choose the fields you would like

 /**
 * We can not change source code so we are adding serializer for a specific type.
 *
 */
public static class JsonSpecificTypeSerializer extends JsonSerializer<SpecificType> {

    @Override
    public void serialize(SpecificType t, JsonGenerator jsonGen, SerializerProvider serializerProvider) throws IOException {
        jsonGen.writeStartObject();
        jsonGen.writeFieldName("field1");
        jsonGen.writeNumber(t.getield1());
        .......

        jsonGen.writeEndObject();
    }

}

/**
 * Customize jackson.
 *
 * adding configuration to jackson without overriding spring boot default conf.
 */
@Bean
public Jackson2ObjectMapperBuilderCustomizer customizeJackson() {
    return jacksonObjectMapperBuilder -> {
        jacksonObjectMapperBuilder.serializerByType(SpecificType.class,
                new JsonSpecificTypeSerializer());
    };
}
user_101622000

There are 2 ways I see how to figure out your issue:

  1. Write custom deserializer for you specific class and register it in Jackson mapper.
  2. Tune up global Jackson mapper to ignore class getters in auto-detection and use only fields.

Please try 2 way with following config:

ObjectMapper mapper = new ObjectMapper();

mapper.setVisibility(JsonMethod.ALL, Visibility.NONE);
mapper.setVisibility(JsonMethod.FIELD, Visibility.ANY);

If you decide to move forward with 1 way, please write here if you need help.

user_57903980
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