Use CodeGen for AOP Fallback

[SentryMan]

The current way of using fallback methods is pretty obtuse, so this adds

• Adds a new annotation to mark a method as a fallback for AOP.
• will generate code to register a fallback method to an invocation
• Adds new method to Invocation to invoke a registered fallback method
• also will use method references in generated proxies if possible

Given stuff like this:

  @MyRetry
  public String retry2(String param0, int param1) {
    retryWithFallbackCounter++;
    throw new IllegalArgumentException("Retry2Fail[" + param0 + "," + param1 + "]");
  }

  @AOPFallback("retry2")
  public String fallbackRetry2(String param0, int param1, Throwable e) {
    return "fallbackRetry2-" + param0 + ":" + param1 + ":" + e.getMessage();
  }

this will get generated

  @Override
  public java.lang.String retry2(String param0, int param1) {
    var call = new Invocation.Call<>(() -> super.retry2(param0, param1))
      .with(this, retry20, param0, param1)
      .fallback(ex -> fallbackRetry2(param0, param1, ex));
    try {
      retry20MyRetry.invoke(call);
      return call.finalResult();
    } catch (RuntimeException ex) {
      ex.addSuppressed(new InvocationException("retry2 proxy threw exception"));
      throw ex;
    } catch (Throwable t) {
      throw new InvocationException("retry2 proxy threw exception", t);
    }
  }

[SentryMan]

@rbygrave waiting for your thoughts before I start on the method signature validation

[rbygrave]

waiting for your thoughts before I start on the method signature validation

So yes I'm happy so far.

start on the method signature validation

I'm not sure specifically what you mean there. Maybe the new methods on Invocation?
edit: Oh, method signature validation ... ok, got it.

[SentryMan]

yeah, I'm good with this

[SentryMan]

Feel free to change the names of method/class names

[rbygrave]

change the names of method/class names

For myself, I feel the ideal name for @AOPFallback would be @Fallback but we can't do that at the moment as that is the name of the deprecated interface that will be removed at some stage.

This is a really nice improvement for doing fallback methods - way better than the existing approach.