Re: Java 17 Records to serialize in GWT

GWT uses either a CustomFieldSerializer implementation to serialize a concrete class or it uses bean serialization. Bean serialization requires a default constructor, serializable fields and final fields are only supported if you enable it.

A CustomFieldSerializer must be written for a concrete class so you cannot provide a serializer for class Record and then expect to send all kinds of records. You can write your own TestRecord_CustomFieldSerializer if you want to send a record via GWT-RPC. It is the same with any other class that you define in your application that need special treatment because it does not have a default constructor. Records just allow you to write a little less code.

https://www.gwtproject.org/doc/latest/DevGuideServerCommunication.html#DevGuideCustomSerialization

-- J.

tekkyru schrieb am Mittwoch, 12. März 2025 um 19:15:06 UTC+1:

Many thanks for supporting Java 17 language features

But in my setup the Java records (new feature) are supported on client side but cannot be passed between server and client:

public record TestRecord(String name, int age) implements IsSerializable {}

interface MyService extends RemoteService {

public TestRecord getTestRecord();

}

The GWT Code server displays an error:

[ERROR] 'com.mycompany.TestRecord' has no instantiable subtypes

Am I doing something wrong or the records cannot be de/serialized yet?

I know they don't have the default constructors, but creating them in javascript should not be affected, and de-serializing a record instance as a call parameter can be (probably) done via reflection.

Best regards

Alex

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