Annotation used to indicate that a POJO-valued property should be serialized "unwrapped" -- that is, if it would be serialized as Object value, its properties are instead included as properties of its containing Object -- and deserialized reproducing "missing" structure. For example, consider case of POJO like:

  public class Parent {
    public int age;
    public Name name;
  }
  public class Name {
    public String first, last;
  }

which would normally be serialized as follows (assuming @JsonUnwrapped had no effect):

  {
    "age" : 18,
    "name" : {
      "first" : "Joey",
      "last" : "Sixpack"
    }
  }

can be changed to this:

  {
    "age" : 18,
    "first" : "Joey",
    "last" : "Sixpack"
  }

by changing Parent class to:

  public class Parent {
    public int age;
    @JsonUnwrapped
    public Name name;
  }

Annotation can only be added to properties, and not classes, as it is contextual. When values are deserialized "wrapping" is applied so that serialized output can be read back in.

Also note that annotation only applies if:

• Value is serialized as an Object value (can not unwrap Array values using this mechanism)
• Reading/writing is done using Jackson standard BeanDeserializer / BeanSerializer; or custom deserializer/serializer MUST explicitly support similar operation.
• Will not work with polymorphic type handling ("polymorphic deserialization")

Specifically note that this annotation WILL NOT WORK for structured types like java.util.Maps or JsonNodes: for these types you will instead need to use JsonAnyGetter and JsonAnySetter to achieve similar operation.