[jboss-dev-forums] [Design of AOP on JBoss (Aspects/JBoss)] - Re: MethodInvocation.getArguments return value for 0 argumen

[flavia.rainone@jboss.com]

Hi!

I changed that in version 2.0, and I added a javadoc documenting the rules related to getArguments():


  | /**
  |     * Returns a non-null array containing all method arguments.
  |     * <p>
  |     * The returned array can be changed by the advice or interceptor accordingly. All
  |     * changes are reflected on joinpoint execution, and are noticed as well by
  |     * other advices and interceptors that are executed after the current one.
  |     * <br>
  |     * However, changes to this array are limited to the scope of current advice
  |     * execution, and must be performed before execution of {@link #invokeNext()},
  |     * {@link #invokeNext(Interceptor[])}, or {@link #invokeTarget()} method.
  |     * Otherwise, inconsistency on joinpoint argument values may be noticed.
  |     *
  |     * @return the method arguments
  |     */
  |    public Object[] getArguments()
  | 

The main cause of this was the use of annotated arguments on before/after advices (new feature of JBoss AOP 2.0). A before/after advice can receive the arguments array as a parameter:

  | public void beforeAdvice(@Args Object[] arguments)
  | {
  |     // do something before joinpoint execution
  | }
  | 

Kabir and I decided that an advice that receives arguments would be called to intercept all types of joinpoint, even though arguments array would be null during a field read joinpoint.

Given that, and considering I couldn't find a documentation on getArguments method returning a null value (please, Kabir, let me know if there is one), I thought that the arguments array should be a non-null value during the interception of other joinpoint types (hence, for methods with no arguments, the arguments array should be an empty array).

Since the intention is to make @Args annotated parameters consistent with [InvocationType].getArguments() and [InvocationType].setArguments() methods, I changed getArguments method to return always a non-null value, as you can see on the javadoc comments (notice that these methods are available only on Invocation classes that are equivalent to joinpoints with a valid arguments list, which excludes the FieldReadInvocation class).

So, this is the reason for which I changed that. I apologize for causing any trouble.

Now, I think we need to decide whether we keep things this way, or we make arguments array null on methods and constructors with an empty argument list.

Any thoughts? Kabir? Clebert?



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