[FIXED] Deserialize generified Enum

Issue

I want to deserialize a generic enum. Sender and receiver use ObjectMapper for MAPPER:

String data = MAPPER.writeValueAsString(new ChangeState(this.state.toString(), this.state.getClass()));
bus.talkAsync(exchangeName, ROUTE_SET_STATE, data);

The Class ChangeState

public record ChangeState<E extends Enum<E>>(String someInfo, String state, Class<E> stateType) {}

The object being sent could look like this:
{"someInfo":"Test","state":"IDLE","stateType":"com.demo.common.states.ServiceAState"} {"someInfo":"Test","state":"SOME","stateType":"com.demo.common.states.ServiceBState"}

I deserialize the message like this:

ChangeState<? extends Enum<?>> changeState = MAPPER.readValue(message, ChangeState.class);

But I'm unable to use the enum afterwards. How can I get back the enum (e.g. with valueOf)?

What I've tried

Cast

The following does not work, because stateType is an unknown class:

Class<? extends Enum<?>> stateType = changeState.stateType();
Enum<?> state = (stateType) changeState.state(); // Error thrown here for the cast type

Transmit the enum as enum

I tried to send the enum directly:

public record ChangeState<E extends Enum<E>>(String someInfo, E state) {}

But this leads to an error, because the enum type can't be identified, since the message looks like this: {"someInfo":"Test","state":"IDLE"}.

Additional

• Each service has it's own state enum, since each service can have different states. The main target ist to make a service, which keeps track of all the states of every other service
• It's a multi module project. Every module uses the com.demo.common module to share classes. The used enums are usable in all modules.
• bus is a RabbitMQ BusConnector.

Solution

When you have a constant name and a class, you can use the static two-argument valueOf method to convert the name to an enum value:

String name = changeState.state();
Class<? extends Enum<?>> type = changeState.stateType();
Enum<?> state = Enum.valueOf(type, name);

Answered By - VGR
Answer Checked By - Pedro (JavaFixing Volunteer)