I'm not 100% sure as I don't remember the details (not having worked on
generators for a while) but I believe you should *always* return a non-null
value (in your case).
IIRC, things go like this:
- you can only generate a given class (by name) per compile. That means
if you need to generate different classes depending on the permutation, you
have to give them different names, and you can detect whether a given class
has already been generated (by another permutation in the same compile) by
doing a null-check on tryCreate's return value.
- the value returned by the generator is the class to use, whichever the
permutation it's been generated in (it doesn't even have to be generated,
you can also just use an existing implementation, but have the generator
dynamically select it rather than relying on –static– rebind rules in the
module's gwt.xml).
So I'd say that in your case, you compile several permutations, and given
the above rules, only the first one will use the generated class, others
will just use GeneratedInterface given that the generator returns 'null'.
On Thursday, April 2, 2015 at 2:17:33 PM UTC+2, Vic wrote:
>
> Hi All,
>
> I am trying to use deferred binding to generate implementation in run-time
> and encountered with one problem. I created pretty simple generator and use
> GWT.create to instantiate a class. I am expecting GWT will provide class
> generated by my generator and it works as expected in dev mode. When I am
> trying to make same in production, for some reason GWT does not provide
> generated version. I have no idea what is wrong, maybe somebody have any
> ideas? Thanks in advance!
> *Class, modified by generator*
>
> public class GeneratedInterface {
>
> public String getValue(){
> return null;
> }
> }
>
>
> *Generator*
>
> public String generate(TreeLogger logger, GeneratorContext ctx, String
> requestedClass) throws UnableToCompleteException {
> JClassType type = ctx.getTypeOracle().findType(requestedClass);
> String packageName = type.getPackage().getName();
> String simpleName = type.getSimpleSourceName() + "_Generated";
> logger.log(TreeLogger.Type.INFO, "Create adapter " + packageName + "." +
> simpleName + " for " + type.getQualifiedSourceName());
> ClassSourceFileComposerFactory composer = new
> ClassSourceFileComposerFactory(packageName, simpleName);
> composer.setSuperclass(GeneratedInterface.class.getName());
> PrintWriter printWriter = ctx.tryCreate(logger, packageName, simpleName);
> String className = null;
> if (printWriter != null) {
> SourceWriter writer = composer.createSourceWriter(ctx, printWriter);
> writer.println("public String getValue() {");
> writer.println(" return \"Test interface\";");
> writer.println("}");
> writer.commit(logger);
> className = composer.getCreatedClassName();
> }
> return className;
> }
>
>
> *EntryPoint*
>
> public class GeneratorTest implements EntryPoint {
>
>
> public void onModuleLoad() {
> GeneratedInterface intf = GWT.create(GeneratedInterface.class);
> log.info("deferred binding: " + intf.getClass().getName());
> log.info("Value = " + intf.getValue());
>
> }
> }
>
>
> *module.xml*
>
> <generate-with class="com.xxx.xxx.gwt.generator.server.TestGenerator">
> <when-type-assignable
> class="com.xxx.xxx.gwt.generator.client.GeneratedInterface"/>
> </generate-with>
>
>
> As you can see, generator just provides implementation for
> GeneratedInterface.getValue()
>
> In case of dev mode, in logs I GWT uses generated class
> Thu Apr 02 15:14:23 MSK 2015
> com.hp.usage.gwt.generator.client.GeneratorTest INFO: deferred binding:
> com.hp.usage.gwt.generator.client.*GeneratedInterface_Generated*
> Thu Apr 02 15:14:23 MSK 2015
> com.hp.usage.gwt.generator.client.GeneratorTest INFO: Value = Test interface
>
> In case of production mode, in logs I GWT does not use generated class
> Thu Apr 02 15:15:53 GMT+300 2015
> com.hp.usage.gwt.generator.client.GeneratorTest INFO: deferred binding:
> com.hp.usage.gwt.generator.client.*GeneratedInterface*
> Thu Apr 02 15:15:53 GMT+300 2015
> com.hp.usage.gwt.generator.client.GeneratorTest INFO: Value = null
>
>
>
>
>
>
>
>
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