-
Notifications
You must be signed in to change notification settings - Fork 3
/
Copy pathprocessor_annotations.html
790 lines (314 loc) · 28.3 KB
/
processor_annotations.html
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
<!DOCTYPE html>
<html lang="en">
<html>
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1">
<meta name="description" content="">
<meta name="keywords" content="processor, processor, processing, annotations">
<title>Processor for annotations | Spoon</title>
<link rel="stylesheet" type="text/css" href="css/syntax.css">
<link rel="stylesheet" type="text/css" href="css/font-awesome.min.css">
<link rel="stylesheet" type="text/css" href="css/bootstrap.min.css">
<link rel="stylesheet" type="text/css" href="css/modern-business.css">
<link rel="stylesheet" type="text/css" href="css/lavish-bootstrap.css">
<link rel="canonical" href="/processor_annotations.html">
<link rel="stylesheet" type="text/css" href="css/customstyles.css">
<link rel="stylesheet" type="text/css" href="css/theme-mauve.css">
<link rel="canonical" href="/processor_annotations.html">
<link rel="alternate" type="application/rss+xml" title="" href="feed.xml" />
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.7.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery-cookie/1.4.1/jquery.cookie.min.js"></script>
<script src="js/jquery.navgoco.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.4/js/bootstrap.min.js"></script>
<script src="js/toc.js"></script>
<script src="js/customscripts.js"></script>
<link rel="shortcut icon" href="favicon.ico" type="image/x-icon">
<!-- HTML5 Shim and Respond.js IE8 support of HTML5 elements and media queries -->
<!-- WARNING: Respond.js doesn't work if you view the page via file:// -->
<!--[if lt IE 9]>
<script src="https://oss.maxcdn.com/libs/html5shiv/3.7.0/html5shiv.js"></script>
<script src="https://oss.maxcdn.com/libs/respond.js/1.4.2/respond.min.js"></script>
<![endif]-->
<script>
$(function () {
$('[data-toggle="tooltip"]').tooltip()
})
</script>
</head>
<body>
<!-- Navigation -->
<nav class="navbar navbar-inverse navbar-fixed-top" role="navigation">
<div class="container topnavlinks">
<div class="navbar-header">
<button type="button" class="navbar-toggle" data-toggle="collapse" data-target="#bs-example-navbar-collapse-1">
<span class="sr-only">Toggle navigation</span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
</button>
<a class="fa fa-home fa-lg navbar-brand" href="index.html"> <span class="projectTitle"> Spoon</span></a>
</div>
<div class="collapse navbar-collapse" id="bs-example-navbar-collapse-1">
<ul class="nav navbar-nav navbar-right">
<!-- entries without drop-downs appear here -->
<!-- conditional logic to control which topnav appears for the audience defined in the configuration file.-->
<li><a href="papers.html">Papers</a></li>
<li><a href="ecosystem.html">Ecosystem</a></li>
<li><a href="about.html">About</a></li>
<li><a href="https://ci.inria.fr/sos/" target="_blank">Jenkins</a></li>
<li><a href="https://github.com/INRIA/spoon" target="_blank">Github</a></li>
<!-- entries with drop-downs appear here -->
<!-- conditional logic to control which topnav appears for the audience defined in the configuration file.-->
<li class="dropdown">
</div>
<!-- /.container -->
</nav>
<!-- Page Content -->
<div class="container">
<div class="col-lg-12"> </div>
<!-- Content Row -->
<div class="row">
<!-- Sidebar Column -->
<div class="col-md-3">
<script>
$(document).ready(function() {
// Initialize navgoco with default options
$("#mysidebar").navgoco({
caretHtml: '',
accordion: true,
openClass: 'active', // open
save: false, // leave false or nav highlighting doesn't work right
cookie: {
name: 'navgoco',
expires: false,
path: '/'
},
slide: {
duration: 400,
easing: 'swing'
}
});
$("#collapseAll").click(function(e) {
e.preventDefault();
$("#mysidebar").navgoco('toggle', false);
});
$("#expandAll").click(function(e) {
e.preventDefault();
$("#mysidebar").navgoco('toggle', true);
});
});
</script>
<ul id="mysidebar" class="nav">
<div class="siteTagline">Spoon</div>
<li><a href="#">Getting started</a>
<ul>
<li><a href="first_analysis_processor.html">Code Analysis</a></li>
</li>
<li><a href="architecture_test.html">Architecture Checking</a></li>
</li>
<li><a href="reflection.html">Runtime Reflection</a></li>
</li>
<li><a href="custom-pretty-printing.html">Custom Java Pretty-Printing</a></li>
</li>
<li><a href="processor.html">Processor for elements</a></li>
</li>
<li><a href="/mvnsites/spoon-core/apidocs" target="_blank">Javadoc</a></li>
</li>
<li><a href="spoon_javadoc.html">Javadoc Analysis</a></li>
</li>
<li><a href="faq.html">FAQ</a></li>
</li>
</ul>
</li>
<li><a href="#">Querying source code elements</a>
<ul>
<li><a href="filter.html">AST Traversing</a></li>
</li>
<li><a href="path.html">AST Paths and Roles</a></li>
</li>
<li><a href="matcher.html">Matcher</a></li>
</li>
<li><a href="pattern.html">Pattern</a></li>
</li>
</ul>
</li>
<li><a href="#">Code Transformation</a>
<ul>
<li><a href="first_transformation.html">Code Transformation</a></li>
</li>
<li><a href="examples.html">Transformation Examples</a></li>
</li>
<li class="active"><a href="processor_annotations.html">Transformation with annotations</a></li>
</li>
<li><a href="template_definition.html">Transformation with Templates</a></li>
</li>
<li><a href="spoon_smpl.html">Semantic patching</a></li>
</li>
<li><a href="pattern.html#generator">Code Generation</a></li>
</li>
<li><a href="testing_quickstart.html">Testing transformations</a></li>
</li>
</ul>
</li>
<li><a href="#">Usage</a>
<ul>
<li><a href="launcher.html">From Java</a></li>
</li>
<li><a href="command_line.html">Command Line</a></li>
</li>
<li><a href="maven.html">From Maven Plugin</a></li>
</li>
<li><a href="gradle.html">From Gradle Plugin</a></li>
</li>
</ul>
</li>
<li><a href="#">Spoon Meta model</a>
<ul>
<li><a href="structural_elements.html">Structural elements</a></li>
</li>
<li><a href="code_elements.html">Code elements</a></li>
</li>
<li><a href="references.html">References</a></li>
</li>
<li><a href="factories.html">Create elements with factories</a></li>
</li>
<li><a href="comments.html">Comments and Positions</a></li>
</li>
</ul>
</li>
</ul>
</div>
<!-- this highlights the active parent class in the navgoco sidebar. this is critical so that the parent expands when you're viewing a page. This must appear below the sidebar code above.-->
<script>$("li.active").parents('li').toggleClass("active");</script>
<!-- Content Column -->
<div class="col-md-9">
<div class="post-header">
<h1 class="post-title-main">Processor for annotations</h1>
</div>
<div class="post-content">
<p>We now discuss how Spoon deals with the processing of annotations.
Java annotations enable developers to embed metadata in their programs.
Although by themselves annotations have no explicit semantics, they can
be used by frameworks as markers for altering the behavior of the programs
that they annotate. This interpretation of annotations can result, for
example, on the configuration of services provided by a middleware
platform or on the alteration of the program source code.</p>
<p>Annotation processing is the process by which a pre-processor modifies an
annotated program as directed by its annotations during a pre-compilation phase.
The Java compiler offers the possibility of compile-time processing of annotations
via the API provided under the <code class="language-plaintext highlighter-rouge">javax.annotation.processing</code> package. Classes
implementing the <code class="language-plaintext highlighter-rouge">javax.annotation.processing.Process</code> interface are used by the
Java compiler to process annotations present in a client program.
The client code is modeled by the classes of the <code class="language-plaintext highlighter-rouge">javax.lang.model</code> package
(although Java 8 has introduced finer-grained annotations, but not on any
arbitrary code elements). It is partially modeled: only types, methods, fields and
parameter declarations can carry annotations. Furthermore, the model does not allow
the developer to modify the client code, it only allows adding new classes.</p>
<p>The Spoon annotation processor overcomes those two limitations: it can handle
annotations on any arbitrary code elements (including within method bodies), and it
supports the modification of the existing code.</p>
<h3 id="annotation-processing-example">Annotation Processing Example</h3>
<p>Spoon provides developers with a way to specify the analyses and transformations
associated with annotations. Annotations are metadata on code that start with <code class="language-plaintext highlighter-rouge">@</code> in Java.
For example, let us consider the example of a design-by-contract annotation.
The annotation <code class="language-plaintext highlighter-rouge">@NotNull</code>, when placed on arguments of a method, will ensure that the argument
is not null when the method is executed. The code below shows both the definition of the
<code class="language-plaintext highlighter-rouge">NotNull</code> annotation type, and an example of its use.</p>
<div class="language-java highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="nd">@Target</span><span class="o">({</span><span class="nc">ElementType</span><span class="o">.</span><span class="na">PARAMETER</span><span class="o">})</span>
<span class="nd">@Retention</span><span class="o">(</span><span class="nc">RetentionPolicy</span><span class="o">.</span><span class="na">SOURCE</span><span class="o">)</span>
<span class="kd">public</span> <span class="nd">@interface</span> <span class="nc">NotNull</span><span class="o">{}</span>
<span class="kd">class</span> <span class="nc">Person</span><span class="o">{</span>
<span class="kd">public</span> <span class="kt">void</span> <span class="nf">marry</span><span class="o">(</span><span class="nd">@NotNull</span> <span class="nc">Person</span> <span class="n">so</span><span class="o">){</span>
<span class="k">if</span><span class="o">(!</span><span class="n">so</span><span class="o">.</span><span class="na">isMarried</span><span class="o">())</span>
<span class="c1">// Marrying logic...</span>
<span class="o">}</span>
<span class="o">}</span>
</code></pre></div></div>
<p>The <code class="language-plaintext highlighter-rouge">NotNull</code> annotation type definition carries two meta-annotations (annotations on annotation
definitions) stating which source code elements can be annotated (line 1), and that the annotation
is intended for compile-time processing (line 2). The <code class="language-plaintext highlighter-rouge">NotNull</code> annotation is used on the argument
of the <code class="language-plaintext highlighter-rouge">marry</code> method of the class <code class="language-plaintext highlighter-rouge">Person</code>. Without annotation processing, if the method <code class="language-plaintext highlighter-rouge">marry</code>
is invoked with a <code class="language-plaintext highlighter-rouge">null</code> reference, a <code class="language-plaintext highlighter-rouge">NullPointerException</code> would be thrown by the Java virtual
machine when invoking the method <code class="language-plaintext highlighter-rouge">isMarried</code> in line 7.</p>
<p>The implementation of such an annotation would not be straightforward using Java’s processing API
since it would not allow us to just insert the NULL check in the body of the annotated method.</p>
<h3 id="the-annotation-processor-interface">The Annotation Processor Interface</h3>
<p>In Spoon, the full code model can be used for compile-time annotation processing. To this end,
Spoon provides a special kind of processor called <code class="language-plaintext highlighter-rouge">AnnotationProcessor</code> whose interface is:</p>
<div class="language-java highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kd">public</span> <span class="kd">interface</span> <span class="nc">AnnotationProcessor</span><span class="o"><</span><span class="no">A</span> <span class="kd">extends</span> <span class="nc">Annotation</span><span class="o">,</span> <span class="no">E</span> <span class="kd">extends</span> <span class="nc">CtElement</span><span class="o">></span> <span class="kd">extends</span> <span class="nc">Processor</span><span class="o"><</span><span class="no">E</span><span class="o">></span> <span class="o">{</span>
<span class="kt">void</span> <span class="nf">process</span><span class="o">(</span><span class="no">A</span> <span class="n">annotation</span><span class="o">,</span> <span class="no">E</span> <span class="n">element</span><span class="o">);</span>
<span class="kt">boolean</span> <span class="nf">inferConsumedAnnotationType</span><span class="o">();</span>
<span class="nc">Set</span><span class="o"><</span><span class="nc">Class</span><span class="o"><?</span> <span class="kd">extends</span> <span class="no">A</span><span class="o">>></span> <span class="nf">getProcessedAnnotationTypes</span><span class="o">();</span>
<span class="nc">Set</span><span class="o"><</span><span class="nc">Class</span><span class="o"><?</span> <span class="kd">extends</span> <span class="no">A</span><span class="o">>></span> <span class="nf">getConsumedAnnotationTypes</span><span class="o">();</span>
<span class="kt">boolean</span> <span class="nf">shoudBeConsumed</span><span class="o">(</span><span class="nc">CtAnnotation</span><span class="o"><?</span> <span class="kd">extends</span> <span class="nc">Annotation</span><span class="o">></span> <span class="n">annotation</span><span class="o">);</span>
<span class="o">}</span>
</code></pre></div></div>
<p>Annotation processors extend normal processors by stating the annotation type those elements must
carry (type parameter <code class="language-plaintext highlighter-rouge">A</code>), in addition of stating the kind of source code element they process
(type parameter <code class="language-plaintext highlighter-rouge">E</code>). The <code class="language-plaintext highlighter-rouge">process</code> method (line 4) receives as arguments both the <code class="language-plaintext highlighter-rouge">CtElement</code> and the
annotation it carries. The remaining four methods (<code class="language-plaintext highlighter-rouge">getProcessedAnnotationTypes</code>, <code class="language-plaintext highlighter-rouge">getConsumedAnnotationTypes</code>,
<code class="language-plaintext highlighter-rouge">inferConsumedAnnotationTypes</code> and <code class="language-plaintext highlighter-rouge">shoudBeConsumed</code>) configure the visiting of the AST during annotation
processing. The Spoon annotation processing runtime is able to infer the type of annotation a processor
handles from its type parameter <code class="language-plaintext highlighter-rouge">A</code>. This restricts each processor to handle a single annotation. To avoid this
restriction, a developer can override the <code class="language-plaintext highlighter-rouge">inferConsumedAnnotationType()</code> method to return <code class="language-plaintext highlighter-rouge">false</code>. When doing
this, Spoon queries the <code class="language-plaintext highlighter-rouge">getProcessedAnnotationTypes()</code> method to find out which annotations are handled by the
processor. Finally, the <code class="language-plaintext highlighter-rouge">getConsumedAnnotationTypes()</code> returns the set of processed annotations that are to be
consumed by the annotation processor. Consumed annotations are not available in later processing rounds.
Similar to standard processors, Spoon provides a default abstract implementation for annotation processors:
<code class="language-plaintext highlighter-rouge">AbstractAnnotationProcessor</code>. It provides facilities for maintaining the list of consumed and processed annotation
types, allowing the developer to concentrate on the implementation of the annotation processing logic.</p>
<p>Going back to our <code class="language-plaintext highlighter-rouge">@NotNull</code> example, we implement a Spoon annotation processor that processes and consumes
<code class="language-plaintext highlighter-rouge">NotNull</code> annotated method parameters, and modifies the source code of the method by inserting an <code class="language-plaintext highlighter-rouge">assert</code> statement
that checks that the argument is not null.</p>
<div class="language-java highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kd">class</span> <span class="nc">NotNullProcessor</span> <span class="kd">extends</span> <span class="nc">AbstractAnnotationProcessor</span><span class="o"><</span><span class="nc">NotNull</span><span class="o">,</span> <span class="nc">CtParameter</span><span class="o">></span> <span class="o">{</span>
<span class="nd">@Override</span>
<span class="kd">public</span> <span class="kt">void</span> <span class="nf">process</span><span class="o">(</span><span class="nc">NotNull</span> <span class="n">anno</span><span class="o">,</span> <span class="nc">CtParameter</span> <span class="n">param</span><span class="o">){</span>
<span class="nc">CtMethod</span><span class="o"><?></span> <span class="n">method</span> <span class="o">=</span> <span class="n">param</span><span class="o">.</span><span class="na">getParent</span><span class="o">(</span><span class="nc">CtMethod</span><span class="o">.</span><span class="na">class</span><span class="o">);</span>
<span class="nc">CtBlock</span><span class="o"><?></span> <span class="n">body</span> <span class="o">=</span> <span class="n">method</span><span class="o">.</span><span class="na">getBlock</span><span class="o">();</span>
<span class="nc">CtAssert</span><span class="o"><?></span> <span class="n">assertion</span> <span class="o">=</span> <span class="n">constructAssertion</span><span class="o">(</span><span class="n">param</span><span class="o">.</span><span class="na">getSimpleName</span><span class="o">());</span>
<span class="n">body</span><span class="o">.</span><span class="na">insertBegin</span><span class="o">(</span><span class="n">assertion</span><span class="o">);</span>
<span class="o">}</span>
<span class="o">}</span>
</code></pre></div></div>
<p>The <code class="language-plaintext highlighter-rouge">NotNullProcessor</code> leverages the default implementation provided by the <code class="language-plaintext highlighter-rouge">AbstractAnnotationProcessor</code> and binds the
type variables representing the annotation to be processed and the annotated code elements to <code class="language-plaintext highlighter-rouge">NotNull</code> and <code class="language-plaintext highlighter-rouge">CtParameter</code>
respectively. The actual processing of the annotation is implemented in the <code class="language-plaintext highlighter-rouge">process(NotNull,CtParameter)</code> method
(lines 10-13). Annotated code is transformed by navigating the AST up from the annotated parameter to the owner method,
and then down to the method’s body code block (lines 10 and 12). The construction of the <code class="language-plaintext highlighter-rouge">assert</code> statement is delegated
to a helper method <code class="language-plaintext highlighter-rouge">constructAssertion(String)</code>, taking as argument the name of the parameter to check. This helper method
constructs an instance of <code class="language-plaintext highlighter-rouge">CtAssert</code> by programmatically constructing the desired boolean expression. Having obtained
the desired assert statement, it is injected at the beginning of the body of the method.</p>
<p>More complex annotation processing scenarios can be tackled with Spoon. For example, when using the <code class="language-plaintext highlighter-rouge">NotNull</code> annotation,
the developer is still responsible for manually inspecting which method parameters to place the annotation on.
A common processing pattern is then to use regular Spoon processors to <code class="language-plaintext highlighter-rouge">auto-annotate</code> the application’s source code.
Such a processor, in our running example, can traverse the body of a method, looking for expressions that send messages
to a parameter. Each of these expressions has as hypothesis that the parameter’s value is not null, and thus should result
in the parameter being annotated with <code class="language-plaintext highlighter-rouge">NotNull</code>.</p>
<p>With this processing pattern, the programmer can use an annotation processor in two ways: either by explicitly and manually
annotating the base program, or by using a processor that analyzes and annotates the program for triggering annotation processors
in an automatic and implicit way. This design decouples the program analysis from the program transformation logics, and leaves
room for manual configuration.</p>
</div>
<hr class="shaded"/>
<footer>
<div class="row">
<div class="col-lg-12 footer">
<a href="https://github.com/INRIA/spoon/issues/new">Contact / Feedback / Question / Bug Report</a><br />
</div>
</div>
</footer>
</div><!-- /.row -->
</div> <!-- /.container -->
</body>
<!-- the google_analytics_id gets auto inserted from the config file -->
<script>
(function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){
(i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o),
m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m)
})(window,document,'script','//www.google-analytics.com/analytics.js','ga');
ga('create', 'UA-24273081-1', 'auto');
ga('send', 'pageview');
</script>
</html>