= AspectJ 1.6.4

_© Copyright 2009 Contributors. All rights reserved._

* xref:#compilation[Compilation times]
* xref:#language[Language enhancements]
* xref:#bugsfixed[Bugs fixed]
* xref:#whatsnext[What's next?]

'''''

[[compilation]]
== Compilation times

In AspectJ 1.6.4 the goal was to improve the IDE experience, through a
combination of improved compilation speed (both full builds and
incremental builds), improved support for multiple-project
configurations, and improved feedback in the editor. The following
sections go into details on each of those topics.

*Full Compilation*

As an example project, all the measurements here are based on the
modified JDT compiler that AspectJ uses internally. It is 1100 source
files and includes aspects that affect around 850 join points. Here are
the full build times in AJDT:

AJDT 1.6.3 (uses AspectJ 1.6.3)

[source, text]
....
21352ms
21597ms
21502ms
....

AJDT 1.6.5dev builds (use AspectJ 1.6.4)

[source, text]
....
19811ms
19802ms
19504ms
....

About 1.5-2 seconds faster for this example.

*Incremental Compilation and multi-project scenarios*

In most common project configurations there are multiple eclipse
projects in some kind of dependency hierarchy. Depending on what changes
in a top level project, those downstream may need to be rebuilt. The
analysis around this area has greatly improved in AspectJ 1.6.4, and
this has resulted in much reduced incremental build times. The example
timed here is around 20 AspectJ projects in a hierarchy, and a change is
made to a source file in the top level project and build times are
observed for the downstream projects.

The timings reported here are accessible to anyone with AJDT installed -
just open the 'AJDT Event Trace View' and it will report ongoing
information about what the compiler/weaver and AJDT are up to. Be aware
that data is only recorded in this view if it is open - so for optimal
performance it should be shutdown, but it is useful for debugging
scenarios or collecting basic benchmark numbers. Within the event trace
view output, the time recorded for 'time spent in AJDE' represents the
time spent in the compiler: analysing what has changed on the classpath,
building code, weaving code.

Initially this is using AJDT 1.6.2 (which embeds AspectJ 1.6.3):

[source, text]
....
Type of change: adding a new method to a type
Project build times (first one is the compile of our change, the rest are for downstream projects):
462ms, 4ms, 145ms, 8ms, 9ms, 287ms, 471ms, 222ms, 1028ms, 143ms, 505ms, 199ms, 261ms, 1224ms,
321ms, 704ms, 75ms, 233ms, 257ms
Summary: Total time spent in the compiler for that change: 6558ms
---
Type of change: whitespace change (adding just a harmless space character)
Project build times (first one is the compile of our change, the rest are for downstream projects):
229ms, 5ms, 10ms, 9ms, 10ms, 79ms, 43ms, 62ms, 80ms, 37ms, 64ms, 32ms, 79ms,
154ms, 94ms, 189ms, 72ms, 144ms, 205ms
Summary: Total time spent in the compiler for that change: 1597ms
....

Now with AspectJ 1.6.5 dev builds (which embed AspectJ 1.6.4):

[source, text]
....
Type of change: adding a new method to a type
Project build times (first one is the compile of our change, the rest are for downstream projects):
288ms, 3ms, 143ms, 2ms, 2ms, 162ms, 244ms, 89ms, 489ms, 113ms, 277ms, 108ms, 143ms, 626ms,
135ms, 260ms, 2ms, 96ms, 6ms
Summary: Total time spent in the compiler for that change: 3188ms down from 6558ms

Type of change: whitespace change (adding just a harmless space character)
Project build times (first one is the compile of our change, the rest are for downstream projects):
101ms, 1ms, 1ms, 1ms, 0ms, 1ms, 1ms, 1ms, 1ms, 1ms, 0ms, 1ms, 1ms, 2ms, 0ms, 1ms, 0ms, 2ms, 2ms
Summary: Total time spent in the compiler for that change: 118ms (down from 1597ms)
....

Improvements all round, and almost instant builds now for whitespace
changes, even in large project setups.

In addition the compilation times are also improved in situations where
AspectJ projects depend upon Java projects and where aspectpath is used.
AJDT 1.6.5 dev builds also include some changes that really speed up
builds.

== Better editor feedback

Under https://bugs.eclipse.org/bugs/show_bug.cgi?id=246393[bug 246393]
the problem has been addressed where sometimes spurious errors would
appear throughout the editor for a file in AJDT when just one single
simple syntax errors exists. More detail on this problem can be found
https://andrewclement.blogspot.com/2009/02/aspectj-fixing-reverse-cascade-errors.html[here].

'''''

[[language]]
== Language Enhancements

*Optimizing support for maintaining per join point state*

The traditional way to maintain state on a per join point basis involves
using the JoinPoint.StaticPart as a key into a map:

[source, java]
....
aspect X pertypewithin(*) {
  Map<JoinPoint.StaticPart,Timer> timerMap = ...

  Object around(): execution(public * *(..)) {
    Timer timerToUse = timerMap.get(thisJoinPointStaticPart);
    timerToUse.start();
    Object o =  proceed();
    timerToUse.stop();
    return o;
  }
}
....

These map lookups are slow. In AspectJ 1.6.4 there is a new getId()
method on the JoinPoint.StaticPart object. The ids for all affected join
points within a target type are unique (and start from 0) - they are
ideal for array lookups. So using this the above aspect can be
rewritten:

[source, java]
....
aspect X pertypewithin(*) {
  Timer[] timerArray = ...

  Object around(): execution(public * *(..)) {
    Timer timerToUse = timerArray[thisJoinPointStaticPart.getId()];
    timerToUse.start();
    Object o =  proceed();
    timerToUse.stop();
    return o;
  }
}
....

much faster. Just be aware that the ids are only unique within an
affected target type - hence the use of pertypewithin in this example to
ensure there is an aspect instance (and so a different array) for each
advised type.

See related https://bugs.eclipse.org/bugs/show_bug.cgi?id=89009[bug
89009] for the full discussion

== @DeclareMixin

The annotation style declare parents support (@DeclareParents) has been
(rightly) criticized because it really does not offer an equivalent to
what is possible with code style declare parents, it really offers a
mixin strategy. It also has limitations such as the delegate instance
used to satisfy any method invocations on an affected target cannot
access the object instance for which it is acting as a delegate. To
address these concerns a proper mixin notation has been introduced that
makes it more clear that a mixin strategy is being employed and it
addresses the problem of the mixin delegate accessing the affected
target instance.

The @DeclareMixin annotation is attached to a factory method which
returns instances of the delegate. Here is a basic example:

[source, java]
....
// The factory method that can build the delegate instance is annotated with @DeclareMixin.
// The annotation value defines the type pattern for targets of the mixin.
// The parameter is the object for which a delegate is being constructed.
// The interface that will be mixed in is the return value of the factory method.
@DeclareMixin("org.xyz..*")
public static SomeInterface createDelegate(Object instance) {
  return new SomeImplementation(instance);
}
....

More examples are xref:../adk15notebook/ataspectj.adoc#ataspectj-itds[here
in the online documentation].

Going forward attempts will be made to try and make @DeclareParents
behave more like code style - if this cannot be done it is likely to be
deprecated.

'''''

[[bugsfixed]]
== Bugs fixed

The complete list of issues resolved for AspectJ 1.6.4 (more than 70)
can be found with this bugzilla query:

* https://bugs.eclipse.org/bugs/buglist.cgi?query_format=advanced&short_desc_type=allwordssubstr&short_desc=&product=AspectJ&target_milestone=1.6.4&long_desc_type=allwordssubstr&long_desc=&bug_file_loc_type=allwordssubstr&bug_file_loc=&status_whiteboard_type=allwordssubstr&status_whiteboard=&keywords_type=allwords&keywords=&bug_status=RESOLVED&bug_status=VERIFIED&bug_status=CLOSED&emailtype1=substring&email1=&emailtype2=substring&email2=&bugidtype=include&bug_id=&votes=&chfieldfrom=&chfieldto=Now&chfieldvalue=&cmdtype=doit&order=Reuse+same+sort+as+last+time&field0-0-0=noop&type0-0-0=noop&value0-0-0=[Bugs
resolved]

'''''

[[whatsnext]]
== What's next?

*More incremental build enhancements*

A number of situations still exist where incremental compile speeds
still needs optimizing, particular when capabilities like aspectpath or
inpath are used.

*Build state persistence*

Between restarts of Eclipse the state of each project is not recorded -
hence full builds are required upon restart. The state (and associated
relationship model) should be persisted between restarts, but both of
these need a review first to ensure they are not larger than they need
to be.

*Memory consumption*

Both for source compilation and load-time weaving scenarios. The size of
the model in the IDE needs reviewing, and also the type map within the
weaver. Although the type map uses Weak/Soft references to try and
better control how it uses memory, the JVM policies for managing these
references vary wildly and so some work needs to be done to allow for
these differences.
