Serialize an object with no data in Jackson

You have to configure your object mapper to support this case.

ObjectMapper objectMapper = ...
  objectMapper.configure(SerializationFeature.FAIL_ON_EMPTY_BEANS, false);

The documentation of this feature can be found here : Fail on empty beans

Feature that determines what happens when no accessors are found for a type (and there are no annotations to indicate it is meant to be serialized). If enabled (default), an exception is thrown to indicate these as non-serializable types; if disabled, they are serialized as empty Objects, i.e. without any properties.

Adding the following annotation onto the class seems to solve the problem:

@JsonAutoDetect(fieldVisibility=JsonAutoDetect.Visibility.NONE)

Adding an unrelated annotated like

@JsonRootName("fred")

also seems to fix it. This seems to match the claim in the JIRA ticket that adding any Jackson annotation to the class will prevent the exception. However, it appears adding annotations within the class does not.

The answer to disable SerializationFeature.FAIL_ON_EMPTY_BEANS is global, and you therefore might not wish to apply it.

The answer to add any serialisation annotation showed the correct (as in: the Javadoc of SerializationFeature.FAIL_ON_EMPTY_BEANS suggests it) way to fix it, but only with a hackish or an unrelated annotation.

By merely adding…

@JsonSerialize

… to my class (not even parenthesēs after it, lest alone arguments!) I was able to produce the same effect (as, again, indicated by the Javadoc of SerializationFeature.FAIL_ON_EMPTY_BEANS).