[resteasy-dev] Lambda question

[Rebecca Searls]

This may be the cause as discussed here
http://stackoverflow.com/questions/22588518/lambda-expression-and-generic-method

      You can't use a lambda expression for a functional interface, if the method in the functional 
      interface has type parameters.  JSE spec section:
      http://docs.oracle.com/javase/specs/jls/se8/html/jls-15.html#jls-15.27.3




----- Original Message -----
> From: "Ron Sigal" <rsigal at redhat.com>
> To: resteasy-dev at lists.jboss.org
> Sent: Monday, April 3, 2017 1:11:38 PM
> Subject: [resteasy-dev] Lambda question
> 
> 
> 
> This question arises in https://issues.jboss.org/browse/RESTEASY-1209
> "org.jboss.resteasy.util.Types#getActualTypeArgumentsOfAnInterface not
> working for lambda's." The reporter wants to do this:
> 
> 
> 
> 
> 
> 
> 
> ResteasyProviderFactory factory = new ResteasyProviderFactory();
> factory.register((ContextResolver<String>) type -> "foo bar");
> 
> 
> 
> but it doesn't work. I find that if I do this:
> 
> 
> 
> ContextResolver<String> resolver1 = new ContextResolver<String>() {
> 
> @Override
> public String getContext(Class<?> type)
> {
> return null;
> }
> };
> for (Type type : resolver1.getClass().getGenericInterfaces())
> {
> System.out.println(type);
> }
> I get
> 
> 
> 
> javax.ws.rs.ext.ContextResolver<java.lang.String>
> but if I do
> 
> 
> 
> ContextResolver<String> resolver2 = type -> "foo";
> for (Type type : resolver2.getClass().getGenericInterfaces())
> {
> System.out.println(type);
> }
> I get
> 
> 
> 
> interface javax.ws.rs.ext.ContextResolver
> Same with
> 
> 
> 
> ContextResolver<String> resolver2 = ((ContextResolver<String>)type -> "foo");
> So, it seems that, for lambdas, Java doesn't keep the implementation type and
> value of the type variable at run time. Does anyone have any ideas or
> tricks?
> 
> Thanks,
> Ron
> 
> 
> 
> 
> --
> My company's smarter than your company (unless you work for Red Hat)
> 
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