Disable message from JSON to POJO with Jackson

How would you deserialize a JSON document for a POJO using Jackson if you don't know exactly which type of POJO to use without validating the message. Is there a way to register a set of POJOs with Jackson so that he can pick one based on the message?

The script I am trying to solve receives JSON messages over a pipe and deserializes into one of several POJOs based on the content of the message.


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3 answers

I am not aware of the mechanism you are describing. I think you will have to inspect the json yourself:

    Map<String, Class<?>> myTypes = ... 
    String json = ...
    JsonNode node = mapper.readTree(json);
    String type = node.get("type").getTextValue();
    Object myobject = mapper.readValue(json, myTypes.get(type));


If you don't have a type field, you will need to validate the fields in the JsonNode to resolve the type.



If you have some flexibility in your JSON library take a look at Jackson . It has a BeanDeserializer that can be used for this purpose.



BeanDeserializer, in Jackson, is deprecated. However, I had the same problem and solved it using Google GSon . Take a look at this example.

Given your POJO datatype:

class BagOfPrimitives {
  private int value1 = 1;
  private String value2 = "abc";
  private transient int value3 = 3;
  BagOfPrimitives() {
    // no-args constructor


  • Serialization

    BagOfPrimitives obj = new BagOfPrimitives();
    Gson gson = new Gson();
    String json = gson.toJson(obj);  // ==> json is {"value1":1,"value2":"abc"}

Note that you cannot serialize objects with circular references, as this will lead to infinite recursion.

  • Deserialization

    BagOfPrimitives obj2 = gson.fromJson(json, BagOfPrimitives.class);



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