<s>
AspectJ	B-Application
is	O
an	O
aspect-oriented	B-Architecture
programming	I-Architecture
(	O
AOP	O
)	O
extension	O
created	O
at	O
PARC	O
for	O
the	O
Java	B-Language
programming	I-Language
language	I-Language
.	O
</s>
<s>
It	O
is	O
available	O
in	O
Eclipse	B-Application
Foundation	I-Application
open-source	O
projects	O
,	O
both	O
stand-alone	O
and	O
integrated	O
into	O
Eclipse	B-Application
.	O
</s>
<s>
AspectJ	B-Application
has	O
become	O
a	O
widely	O
used	O
de	O
facto	O
standard	O
for	O
AOP	O
by	O
emphasizing	O
simplicity	O
and	O
usability	O
for	O
end	O
users	O
.	O
</s>
<s>
It	O
uses	O
Java-like	O
syntax	O
,	O
and	O
included	O
IDE	O
integrations	O
for	O
displaying	O
crosscutting	B-Application
structure	I-Application
since	O
its	O
initial	O
public	O
release	O
in	O
2001	O
.	O
</s>
<s>
All	O
valid	O
Java	B-Language
programs	O
are	O
also	O
valid	O
AspectJ	B-Application
programs	O
,	O
but	O
AspectJ	B-Application
lets	O
programmers	O
define	O
special	O
constructs	O
called	O
aspects	O
.	O
</s>
<s>
This	O
example	O
adds	O
an	O
acceptVisitor	O
(	O
see	O
visitor	B-Language
pattern	I-Language
)	O
method	O
to	O
the	O
Point	O
class	O
:	O
</s>
<s>
Pointcuts	B-Application
Allow	O
a	O
programmer	O
to	O
specify	O
join	B-Application
points	I-Application
(	O
well-defined	O
moments	O
in	O
the	O
execution	O
of	O
a	O
program	O
,	O
like	O
method	O
call	O
,	O
object	O
instantiation	O
,	O
or	O
variable	O
access	O
)	O
.	O
</s>
<s>
All	O
pointcuts	B-Application
are	O
expressions	O
(	O
quantifications	O
)	O
that	O
determine	O
whether	O
a	O
given	O
join	B-Application
point	I-Application
matches	O
.	O
</s>
<s>
Advices	B-Application
Allow	O
a	O
programmer	O
to	O
specify	O
code	O
to	O
run	O
at	O
a	O
join	B-Application
point	I-Application
matched	O
by	O
a	O
pointcut	B-Application
.	O
</s>
<s>
The	O
actions	O
can	O
be	O
performed	O
before	O
,	O
after	O
,	O
or	O
around	O
the	O
specified	O
join	B-Application
point	I-Application
.	O
</s>
<s>
Here	O
,	O
the	O
advice	O
refreshes	O
the	O
display	O
every	O
time	O
something	O
on	O
Point	O
is	O
set	O
,	O
using	O
the	O
pointcut	B-Application
declared	O
above	O
:	O
</s>
<s>
AspectJ	B-Application
also	O
supports	O
limited	O
forms	O
of	O
pointcut-based	O
static	O
checking	O
and	O
aspect	O
reuse	O
(	O
by	O
inheritance	O
)	O
.	O
</s>
<s>
AspectJ	B-Application
can	O
be	O
implemented	O
in	O
many	O
ways	O
,	O
including	O
source-weaving	O
or	O
bytecode-weaving	O
,	O
and	O
directly	O
in	O
the	O
virtual	B-Architecture
machine	I-Architecture
(	O
VM	O
)	O
.	O
</s>
<s>
In	O
all	O
cases	O
,	O
the	O
AspectJ	B-Application
program	O
becomes	O
a	O
valid	O
Java	B-Language
program	O
that	O
runs	O
in	O
a	O
Java	B-Language
VM	O
.	O
</s>
<s>
Supporting	O
multiple	O
implementations	O
allows	O
the	O
language	O
to	O
grow	O
as	O
technology	O
changes	O
,	O
and	O
being	O
Java-compatible	O
ensures	O
platform	O
availability	O
.	O
</s>
<s>
The	O
original	O
Xerox	O
AspectJ	B-Application
implementation	O
used	O
source	O
weaving	O
,	O
which	O
required	O
access	O
to	O
source	O
code	O
.	O
</s>
<s>
When	O
Xerox	O
contributed	O
the	O
code	O
to	O
Eclipse	B-Application
,	O
AspectJ	B-Application
was	O
reimplemented	O
using	O
the	O
Eclipse	B-Application
Java	I-Application
compiler	O
and	O
a	O
bytecode	O
weaver	O
based	O
on	O
BCEL	O
,	O
so	O
developers	O
could	O
write	O
aspects	O
for	O
code	O
in	O
binary	O
(	O
.class	O
)	O
form	O
.	O
</s>
<s>
At	O
this	O
time	O
the	O
AspectJ	B-Application
language	O
was	O
restricted	O
to	O
support	O
a	O
per-class	O
model	O
essential	O
for	O
incremental	O
compilation	O
and	O
load-time	O
weaving	O
.	O
</s>
<s>
This	O
made	O
IDE	O
integrations	O
as	O
responsive	O
as	O
their	O
Java	B-Language
counterparts	O
,	O
and	O
it	O
let	O
developers	O
deploy	O
aspects	O
without	O
altering	O
the	O
build	O
process	O
.	O
</s>
<s>
This	O
led	O
to	O
increased	O
adoption	O
,	O
as	O
AspectJ	B-Application
became	O
usable	O
for	O
impatient	O
Java	B-Language
programmers	O
and	O
enterprise-level	O
deployments	O
.	O
</s>
<s>
Since	O
then	O
,	O
the	O
Eclipse	B-Application
team	O
has	O
increased	O
performance	O
and	O
correctness	O
,	O
upgraded	O
the	O
AspectJ	B-Application
language	O
to	O
support	O
Java	B-Language
5	O
language	O
features	O
like	O
generics	B-Language
and	O
annotations	B-Language
,	O
and	O
integrated	O
annotation-style	O
pure-java	O
aspects	O
from	O
AspectWerkz	B-Application
.	O
</s>
<s>
The	O
Eclipse	B-Application
project	O
supports	O
both	O
command-line	O
and	O
Ant	B-Application
interfaces	O
.	O
</s>
<s>
A	O
related	O
Eclipse	B-Application
project	O
has	O
steadily	O
improved	O
the	O
Eclipse	B-Application
IDE	I-Application
support	O
for	O
AspectJ	B-Application
(	O
called	O
AspectJ	B-Application
Development	O
Tools	O
(	O
AJDT	O
)	O
)	O
and	O
other	O
providers	O
of	O
crosscutting	B-Application
structure	I-Application
.	O
</s>
<s>
IDE	O
support	O
for	O
emacs	B-Application
,	O
NetBeans	B-Application
,	O
and	O
JBuilder	B-Application
foundered	O
when	O
Xerox	O
put	O
them	O
into	O
open	O
source	O
,	O
but	O
support	O
for	O
Oracle	O
's	O
JDeveloper	O
did	O
appear	O
.	O
</s>
<s>
IDE	O
support	O
has	O
been	O
key	O
to	O
Java	B-Language
programmers	O
using	O
AspectJ	B-Application
and	O
understanding	O
crosscutting	B-Application
concerns	I-Application
.	O
</s>
<s>
BEA	O
has	O
offered	O
limited	O
VM	O
support	O
for	O
aspect-oriented	B-Architecture
extensions	O
,	O
but	O
for	O
extensions	O
supported	O
in	O
all	O
Java	B-Language
VM	O
's	O
would	O
require	O
agreement	O
through	O
Sun	O
's	O
Java	B-Language
Community	O
Process	O
(	O
see	O
also	O
the	O
java.lang.instrument	O
package	O
available	O
since	O
Java	B-Language
SE	O
5	O
—	O
which	O
is	O
a	O
common	O
ground	O
for	O
JVM	O
load-time	O
instrumentation	O
)	O
.	O
</s>
<s>
Academic	O
interest	O
in	O
the	O
semantics	O
and	O
implementation	O
of	O
aspect-oriented	B-Architecture
languages	I-Architecture
has	O
surrounded	O
AspectJ	B-Application
since	O
its	O
release	O
.	O
</s>
<s>
The	O
leading	O
research	O
implementation	O
of	O
AspectJ	B-Application
is	O
the	O
,	O
or	O
abc	O
;	O
it	O
supports	O
extensions	O
for	O
changing	O
the	O
syntax	O
and	O
semantics	O
of	O
the	O
language	O
and	O
forms	O
the	O
basis	O
for	O
many	O
AOP	O
experiments	O
that	O
the	O
AspectJ	B-Application
team	O
can	O
no	O
longer	O
support	O
,	O
given	O
its	O
broad	O
user	O
base	O
.	O
</s>
<s>
Many	O
programmers	O
discover	O
AspectJ	B-Application
as	O
an	O
enabling	O
technology	O
for	O
other	O
projects	O
,	O
most	O
notably	O
Spring	O
AOP	O
.	O
</s>
<s>
A	O
sister	O
Spring	O
project	O
,	O
Spring	B-Language
Roo	I-Language
,	O
automatically	O
maintains	O
AspectJ	B-Application
inter-type	B-Language
declarations	I-Language
as	O
its	O
principal	O
code	O
generation	O
output	O
.	O
</s>
<s>
Gregor	O
Kiczales	O
started	O
and	O
led	O
the	O
Xerox	O
PARC	O
team	O
that	O
eventually	O
developed	O
AspectJ	B-Application
.	O
</s>
<s>
He	O
coined	O
the	O
term	O
crosscutting	B-Application
.	O
</s>
<s>
Fourth	O
on	O
the	O
team	O
,	O
Chris	B-Application
Maeda	I-Application
coined	O
the	O
term	O
aspect-oriented	B-Architecture
programming	I-Architecture
.	O
</s>
<s>
AspectWerkz	B-Application
is	O
a	O
dynamic	O
,	O
lightweight	O
and	O
high-performance	O
AOP/AOSD	B-Architecture
framework	O
for	O
Java	B-Language
.	O
</s>
<s>
It	O
has	O
been	O
merged	O
with	O
the	O
AspectJ	B-Application
project	O
,	O
which	O
supports	O
AspectWerkz	B-Application
functionality	O
since	O
AspectJ	B-Application
5	O
.	O
</s>
<s>
Jonas	O
Boner	O
and	O
Alex	O
Vasseur	O
engineered	O
the	O
AspectWerkz	B-Application
project	O
,	O
and	O
later	O
contributed	O
to	O
the	O
AspectJ	B-Application
project	O
when	O
it	O
merged	O
in	O
the	O
AspectWerkz	B-Application
annotation	O
style	O
and	O
load-time	O
weaving	O
support	O
.	O
</s>
<s>
Unlike	O
AspectJ	B-Application
prior	O
to	O
version	O
5	O
,	O
AspectWerkz	B-Application
did	O
not	O
add	O
any	O
new	O
language	O
constructs	O
to	O
Java	B-Language
,	O
but	O
instead	O
supported	O
declaration	O
of	O
aspects	O
within	O
Java	B-Language
annotations	I-Language
.	O
</s>
<s>
It	O
utilizes	O
bytecode	O
modification	O
to	O
weave	B-Application
classes	O
at	O
project	O
build-time	O
,	O
class	O
load	O
time	O
,	O
as	O
well	O
as	O
runtime	B-Library
.	O
</s>
<s>
Aspects	O
can	O
be	O
defined	O
using	O
either	O
Java	B-Language
annotations	I-Language
(	O
introduced	O
with	O
Java	B-Language
5	O
)	O
,	O
Java	B-Language
1.3/1.4	O
custom	O
doclet	O
or	O
a	O
simple	O
XML	O
definition	O
file	O
.	O
</s>
<s>
AspectWerkz	B-Application
provides	O
an	O
API	O
to	O
use	O
the	O
very	O
same	O
aspects	O
for	O
proxies	O
,	O
hence	O
providing	O
a	O
transparent	O
experience	O
,	O
allowing	O
a	O
smooth	O
transition	O
for	O
users	O
familiar	O
with	O
proxies	O
.	O
</s>
<s>
AspectWerkz	B-Application
is	O
free	B-Application
software	I-Application
.	O
</s>
<s>
The	O
LGPL-style	O
license	O
allows	O
the	O
use	O
of	O
AspectWerkz	B-Application
2.0	O
in	O
both	O
commercial	O
and	O
open	O
source	O
projects	O
.	O
</s>
