Re: Generator - Best way to support custom user extension

Thanks for your answer!

GWT-RPC does this by convention. The custom serializer must be in the same package as the class it (de)serializes and is named <class name>_CustomFieldSerializer, e.g. ImmutableSet_CustomFieldSerializer.

Is it not easier to use the TypeOracle to find CustomFieldSerializer JClassType and get all its subtype with JClassType.getSubtypes() ? This way you can put your custom serializers anywhere with the name you like. 

 

I wouldn't use an annotation because a guava collection could be used by a large amount of classes so you only want to define the serializer once for a given collection type. To do so you would need some kind of a "configuration" class where you can put annotations once. Or use such a configuration class the google-gin way: 

void configure() {

  serialize(ImmutableSet.class).with(ImmutableSetJsonSerializer.class).

}

How do you give the configuration class to the generator ? With configuration property like below ?

And how does it work ? The generator get the full qualified class name, instantiate the class and get the configured serializer from the internal map ? Since it's a Class, you then use the TypeOracle to get the corresponding JClassType ?

 

If you don't want a configuration class then you could also define a configuration property in your gwt module xml instead. That property could then be filled by users of your library. The property values should point to full qualified class names of custom serializers. google-gin also has an example of this technique because you could define a configuration property and then reference it on the Ginjector like:

@GinModules(value = MyModule.class, properties = { "my.google.gin.extention.property1", "my.google.gin.extention.property2" }

public interface MyInjector extends Ginjector {}

<define-configuration-property name="my.google.gin.extention.property1" is-multi-valued="true" /> (would go in your library gwt xml)

<extend-configuration-property name="my.google.gin.extention.property1" value="com.example.ExtentionModule" /> (thats what a library user would need to define in their gwt xml)

 

I didn't know you could do that in Gin, that's nice! (I'm already thinking how I could use that to split a big application I'm working on)

For all these configuration methods, is there some built-in method inside generators to cache the configuration so you compute it only once ? I imagine creating a Map<JClassType, JClassType> (type -> serializer) and giving that map to some kind of compilation context.

Thanks again for your answer. 

 

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