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author | duke |
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date | Sat, 01 Dec 2007 00:00:00 +0000 |
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1 <html> | |
2 <head> | |
3 <title> | |
4 JavaScript interface to Hotspot Serviceability Agent | |
5 </title> | |
6 </head> | |
7 <body> | |
8 <h1>JavaScript interface to Hotspot Serviceability Agent</h1> | |
9 | |
10 <p> | |
11 Serviceability Agent (SA) provides Java API and tools to diagnose HotSpot Virtual Machine and | |
12 Java apps running on it. SA is a snapshot debugger -- can be used to observe state of a frozen java process or java core dump. | |
13 </p> | |
14 | |
15 <h2>Existing SA APIs</h2> | |
16 <p> | |
17 There are two application programmer interfaces (APIs) for SA: | |
18 <dl> | |
19 <dt>1. Private java API | |
20 </dt> | |
21 <dd> | |
22 This tries to mimic hotspot VM's internal C++ classes and methods. Because VM data structures | |
23 are a moving target, this API can never be 'stable'! Besides, to use SA's private API knowledge of | |
24 HotSpot code base is essential. | |
25 </dd> | |
26 <dt>2. SA-JDI -- Java Debugger Interface read-only subset API | |
27 </dt> | |
28 <dd> | |
29 This is read-only subset of JDI (Java Debugger Interface) | |
30 This is a standardized interface to get java level state of a java process or java core dump. While this | |
31 interface is useful, this misses parts of java level state from target process or core such as | |
32 <ul> | |
33 <li>heap walking interface -- only objects traceable to static variables (of classes) and local | |
34 variables of stack frames can be accessed. | |
35 <li>re-constructing .class from debuggee are missing. | |
36 <li>re-constructing object mirrors for Java objects of the debuggee. | |
37 </ul> | |
38 </dd> | |
39 </dl> | |
40 </p> | |
41 | |
42 <h2>SA Scripting interface</h2> | |
43 | |
44 <p> | |
45 Traditionally, platform debuggers such as dbx, gdb and Solaris mdb (Module Debugger), provide a scripting | |
46 language interface. Scripting language interface provides easy-to-use, dynamically typed | |
47 interface to access data structures from debuggee. dbx and mdb even allow user to write | |
48 C/C++ modules to extend the scripting language commands. | |
49 </p> | |
50 | |
51 <p> | |
52 SA provides SOQL - Simple Object Query Language -- a SQL-like query language to access | |
53 Java heap as an object database. SA's main GUI (HSDB) also exposes scripting interface of underlying debugger such as dbx, windbg. | |
54 But to use this interface, user has to learn scripting interface of multiple debugger back-ends such as dbx, windbg. | |
55 And these scripting interfaces are 'raw' in the sense that no java state is exposed -- only C/C++ state of VM is exposed. | |
56 Higher level SA services are not available through scripting interface. | |
57 </p> | |
58 | |
59 <p> | |
60 <b>jsdb -- JavaScript Debugger</b> attempts to provide JavaScript interface to SA. | |
61 jsdb provides | |
62 | |
63 <ul> | |
64 <li>high-level hotspot (and SA) independent scripting interface | |
65 <li>low-level SA-aware scripting interface. | |
66 </ul> | |
67 </p> | |
68 | |
69 <h2>High level interface (Java State)</h2> | |
70 | |
71 <b>jsdb</b> is a command line <a href="http://www.ecma-international.org/publications/standards/Ecma-262.htm">JavaScript</a> shell based on | |
72 <a href="http://www.mozilla.org/rhino/">Mozilla's Rhino JavaScript Engine</a>. | |
73 This command line utility attaches to Java process or core file or remote debug server and waits for user input. | |
74 This shell supports the following global functions and objects in addition to the standard JavaScript functions and | |
75 objects: | |
76 | |
77 <h3>jdsb globals</h3> | |
78 | |
79 <table border="1"> | |
80 <tr> | |
81 <th>Function/Variable</th> | |
82 <th>Description</th> | |
83 </tr> | |
84 <tr> | |
85 <td> | |
86 address(jobject) | |
87 </td> | |
88 <td> | |
89 function that returns the address of the Java object as a string | |
90 </td> | |
91 </tr> | |
92 <td> | |
93 classof(jobject) | |
94 </td> | |
95 <td> | |
96 function that returns the JavaScript object that represents class object of the Java object | |
97 </td> | |
98 </tr> | |
99 <td> | |
100 dumpClass(jclass,[dir]) | |
101 </td> | |
102 <td> | |
103 function that writes .class for the given Java Class. Optionally (second arg) accepts the directory where the | |
104 .class has to be written. | |
105 </td> | |
106 </tr> | |
107 <td> | |
108 help() | |
109 </td> | |
110 <td> | |
111 function that prints help message for global functions and objects | |
112 </td> | |
113 </tr> | |
114 <tr> | |
115 <td> | |
116 identityHash(jobject) | |
117 </td> | |
118 <td> | |
119 function that returns the identity hashCode of the Java object | |
120 </td> | |
121 </tr> | |
122 <tr> | |
123 <td> | |
124 mirror(jobject) | |
125 </td> | |
126 <td> | |
127 function that returns a local mirror of the Java object. | |
128 </td> | |
129 </tr> | |
130 <tr> | |
131 <td> | |
132 load([file1, file2,...]) | |
133 </td> | |
134 <td> | |
135 function that loads zero or more JavaScript file(s). With no arguments, reads <stdin> for | |
136 JavaScript code. | |
137 </td> | |
138 </tr> | |
139 <tr> | |
140 <td> | |
141 object(string) | |
142 </td> | |
143 <td> | |
144 function that converts a string address into Java object | |
145 </td> | |
146 </tr> | |
147 <tr> | |
148 <td> | |
149 owner(jobject) | |
150 </td> | |
151 <td> | |
152 function that returns the owner thread of this monitor or null | |
153 </td> | |
154 </tr> | |
155 <tr> | |
156 <td> | |
157 sizeof(jobject) | |
158 </td> | |
159 <td> | |
160 function that returns the size of Java object in bytes | |
161 </td> | |
162 </tr> | |
163 <tr> | |
164 <td> | |
165 staticof(jclass, field) | |
166 </td> | |
167 <td> | |
168 function that returns the value of given field of the given Java class | |
169 </td> | |
170 </tr> | |
171 <tr> | |
172 <td> | |
173 print(expr1, expr2,...) | |
174 </td> | |
175 <td> | |
176 function that prints zero or more JavaScript expressions after converting those as strings | |
177 </td> | |
178 </tr> | |
179 <tr> | |
180 <td> | |
181 println(expr1, expr2..) | |
182 </td> | |
183 <td> | |
184 function that same as print, but prints a newline at the end | |
185 </td> | |
186 </tr> | |
187 <tr> | |
188 <td> | |
189 read([prompt]) | |
190 </td> | |
191 <td> | |
192 function that reads a single line from standard input | |
193 </td> | |
194 </tr> | |
195 <tr> | |
196 <td> | |
197 quit() | |
198 </td> | |
199 <td> | |
200 function that quits the interactive load call as well as the shell | |
201 </td> | |
202 </tr> | |
203 <tr> | |
204 <td> | |
205 jvm | |
206 </td> | |
207 <td> | |
208 variable -- a JavaScript object that represents the target jvm that is being debugged | |
209 </td> | |
210 </tr> | |
211 </table> | |
212 | |
213 <h3>jvm object</h3> | |
214 | |
215 <p> | |
216 jvm object supports the following read-only properties. | |
217 </p> | |
218 | |
219 <table border="1"> | |
220 <tr> | |
221 <th> | |
222 Property name | |
223 </th> | |
224 <th> | |
225 Description | |
226 </th> | |
227 </tr> | |
228 <tr> | |
229 <td> | |
230 threads | |
231 </td> | |
232 <td> | |
233 array of Java threads from the debuggee | |
234 </td> | |
235 </tr> | |
236 <tr> | |
237 <td> | |
238 heap | |
239 </td> | |
240 <td> | |
241 object representing the heap of the debuggee | |
242 </td> | |
243 </tr> | |
244 <tr> | |
245 <td> | |
246 type | |
247 </td> | |
248 <td> | |
249 string value that is either "Server" or "Client" or "Core" -- the flavour of debuggee VM | |
250 </td> | |
251 </tr> | |
252 <tr> | |
253 <td> | |
254 bootClassPath | |
255 </td> | |
256 <td> | |
257 string value of bootclasspath of the debuggee | |
258 </td> | |
259 </tr> | |
260 <tr> | |
261 <td> | |
262 cpu | |
263 </td> | |
264 <td> | |
265 string value of cpu on which the debuggee runs/ran | |
266 </td> | |
267 </tr> | |
268 <tr> | |
269 <td> | |
270 sysProps | |
271 </td> | |
272 <td> | |
273 name-value pairs (JavaScript associative array) of Java System properties of the debuggee | |
274 </td> | |
275 </tr> | |
276 <tr> | |
277 <td> | |
278 addressSize | |
279 </td> | |
280 <td> | |
281 int value -- 32 for 32 bit debuggee, 64 for 64 bit debuggee | |
282 </td> | |
283 </tr> | |
284 <tr> | |
285 <td> | |
286 os | |
287 </td> | |
288 <td> | |
289 string value of OS on which the debuggee runs/ran | |
290 </td> | |
291 </tr> | |
292 <tr> | |
293 <td> | |
294 buildInfo | |
295 </td> | |
296 <td> | |
297 internal build info string from debuggee | |
298 </td> | |
299 </tr> | |
300 <tr> | |
301 <td> | |
302 flags | |
303 </td> | |
304 <td> | |
305 name-value pairs (JavaScript associative array) of JVM command line flags of the debuggee | |
306 </td> | |
307 </tr> | |
308 <tr> | |
309 <td> | |
310 classPath | |
311 </td> | |
312 <td> | |
313 string value of classpath of the debuggee | |
314 </td> | |
315 </tr> | |
316 <tr> | |
317 <td> | |
318 userDir | |
319 </td> | |
320 <td> | |
321 string value of user.dir System property of the debuggee | |
322 </td> | |
323 </tr> | |
324 </table> | |
325 | |
326 <h3>heap object</h3> | |
327 | |
328 <p> | |
329 heap object represents Java heap of the debuggee VM | |
330 </p> | |
331 <table border="1"> | |
332 <tr> | |
333 <th> | |
334 Function or property name | |
335 </th> | |
336 <th> | |
337 Description | |
338 </th> | |
339 </tr> | |
340 <tr> | |
341 <td> | |
342 capacity | |
343 </td> | |
344 <td> | |
345 byte size of capacity of the heap | |
346 </td> | |
347 </tr> | |
348 <tr> | |
349 <td> | |
350 used | |
351 </td> | |
352 <td> | |
353 byte size of used portion (of live objects) of the heap | |
354 </td> | |
355 </tr> | |
356 <tr> | |
357 <td> | |
358 forEachObject(func, [class], [include subtypes -- true|false]) | |
359 </td> | |
360 <td> | |
361 This function accepts a callback function 'func' and optionally class name and boolean arguments. | |
362 This function calls the callback for each Java object in the debuggee's heap. The optional class | |
363 argument may be used to receive objects of given class only. The third arguments specifies whether | |
364 to include objects of subtype of given class [or interface] or not. The default value of class is "java.lang.Object" | |
365 and and that of the third argument is true. i.e., by default all objects are included. | |
366 </td> | |
367 </tr> | |
368 <tr> | |
369 <td> | |
370 forEachClass(func, [initiating loader -- true|false]) | |
371 </td> | |
372 <td> | |
373 This function accepts a callback function 'func'. This function iterates through the classes of the debuggee and calls the | |
374 callback for each class. The second parameter tells whether to pass initiating loader to the iterator callback or not. | |
375 </td> | |
376 </tr> | |
377 </table> | |
378 | |
379 <h3>Accessing Java objects and arrays in script</h3> | |
380 | |
381 <p> | |
382 From a given Java object, we can access all fields of the Java object by usual '.' operator. i.e., if you got a Java object | |
383 called 'o' of type java.lang.Thread from debuggee, you can access 'stackSize' field by o.stackSize syntax. Similarly, length of Java array | |
384 objects can be accessed by length property. And array indexing follows usual syntax. i.e., n'th element of array 'a' is | |
385 accessed by a[n]. | |
386 </p> | |
387 | |
388 <h3>jvm.threads array</h3> | |
389 | |
390 <p> | |
391 This is a JavaScript array of Java threads of the debuggee. As usual, 'length' property tells the number of threads and individual | |
392 threads may be accessed by index operator -- i.e, jvm.threads[0] returns the first thread. | |
393 </p> | |
394 | |
395 <h3>thread object</h3> | |
396 | |
397 | |
398 <p> | |
399 In addition to the fields of java.lang.Thread (or subclass) fields, thread objects have two additional properties. | |
400 | |
401 <ul> | |
402 <li>frames -- array of stack frame objects | |
403 <li>monitors -- array of monitor objects owned by the thread | |
404 </ul> | |
405 | |
406 </p> | |
407 | |
408 <h3>stack frame object</h3> | |
409 | |
410 <table border="1"> | |
411 <tr> | |
412 <th> | |
413 Property name | |
414 </th> | |
415 <th> | |
416 Description | |
417 </th> | |
418 </tr> | |
419 <td> | |
420 thisObject | |
421 </td> | |
422 <td> | |
423 Object representing 'this' of the current frame [will be null for static methods] | |
424 </td> | |
425 </tr> | |
426 <tr> | |
427 <td> | |
428 locals | |
429 </td> | |
430 <td> | |
431 name-value pairs of local variables [JavaScript associative array] | |
432 </td> | |
433 </tr> | |
434 <tr> | |
435 <td> | |
436 line | |
437 </td> | |
438 <td> | |
439 Java source line number at which the frame is executing | |
440 </td> | |
441 </tr> | |
442 <tr> | |
443 <td> | |
444 bci | |
445 </td> | |
446 <td> | |
447 byte code index of the bytecode that the frame is executing | |
448 </td> | |
449 </tr> | |
450 <tr> | |
451 <td> | |
452 thread | |
453 </td> | |
454 <td> | |
455 thread to which this frame belongs | |
456 </td> | |
457 </tr> | |
458 <tr> | |
459 <td> | |
460 method | |
461 </td> | |
462 <td> | |
463 Java method that the frame is executing | |
464 </td> | |
465 </tr> | |
466 </table> | |
467 | |
468 <h3>method object</h3> | |
469 | |
470 <p> | |
471 method object represents a Java method of debuggee | |
472 </p> | |
473 | |
474 <table border="1"> | |
475 <tr> | |
476 <th> | |
477 Property name | |
478 </th> | |
479 <th> | |
480 Description | |
481 </th> | |
482 </tr> | |
483 <tr> | |
484 <td> | |
485 isStatic | |
486 </td> | |
487 <td> | |
488 boolean - true for static methods and false for non-static methods | |
489 </td> | |
490 </tr> | |
491 | |
492 <tr> | |
493 <td> | |
494 isSynchronized | |
495 </td> | |
496 <td> | |
497 boolean - true for synchronized methods and false for non-synchronized methods | |
498 </td> | |
499 </tr> | |
500 | |
501 <tr> | |
502 <td> | |
503 isNative | |
504 </td> | |
505 <td> | |
506 boolean - true for native methods and false for non-native methods | |
507 </td> | |
508 </tr> | |
509 | |
510 <tr> | |
511 <td> | |
512 isProtected | |
513 </td> | |
514 <td> | |
515 boolean - true for protected methods and false for non-protected methods | |
516 </td> | |
517 </tr> | |
518 | |
519 <tr> | |
520 <td> | |
521 isPrivate | |
522 </td> | |
523 <td> | |
524 boolean - true for private methods and false for non-private methods | |
525 </td> | |
526 </tr> | |
527 | |
528 <tr> | |
529 <td> | |
530 isSynthetic | |
531 </td> | |
532 <td> | |
533 boolean - true for Javac generated synthetic methods and false for non-synthetic methods | |
534 </td> | |
535 </tr> | |
536 | |
537 <tr> | |
538 <td> | |
539 isPackagePrivate | |
540 </td> | |
541 <td> | |
542 boolean - true for package-private methods and false for non-package-private methods | |
543 </td> | |
544 </tr> | |
545 | |
546 <tr> | |
547 <td> | |
548 isPublic | |
549 </td> | |
550 <td> | |
551 boolean - true for public methods and false for non-public methods | |
552 </td> | |
553 </tr> | |
554 | |
555 <tr> | |
556 <td> | |
557 holder | |
558 </td> | |
559 <td> | |
560 an object that represents Class that contains this method | |
561 </td> | |
562 </tr> | |
563 | |
564 <tr> | |
565 <td> | |
566 signature | |
567 </td> | |
568 <td> | |
569 string -- signature of this method | |
570 </td> | |
571 </tr> | |
572 | |
573 <tr> | |
574 <td> | |
575 isObsolete | |
576 </td> | |
577 <td> | |
578 boolean - true for obsolete (hotswapped) methods and false for non-obsolete methods | |
579 </td> | |
580 </tr> | |
581 | |
582 <tr> | |
583 <td> | |
584 isStrict | |
585 </td> | |
586 <td> | |
587 boolean - true for strictfp methods and false for non-strictfp methods | |
588 </td> | |
589 </tr> | |
590 | |
591 <tr> | |
592 <td> | |
593 isFinal | |
594 </td> | |
595 <td> | |
596 boolean - true for final methods and false for non-final methods | |
597 </td> | |
598 </tr> | |
599 | |
600 <tr> | |
601 <td> | |
602 name | |
603 </td> | |
604 <td> | |
605 string - name of this method | |
606 </td> | |
607 </tr> | |
608 </table> | |
609 | |
610 <h3>class object</h3> | |
611 | |
612 <p> | |
613 A class object represents loaded Java class in debuggee VM. This represents java.lang.Class instance in the debuggee. | |
614 This is type of return value of classof global function. Also, method.holder property and field.holder are | |
615 of this type. | |
616 </p> | |
617 | |
618 <table border="1"> | |
619 <tr> | |
620 <th> | |
621 Property name | |
622 </th> | |
623 <th> | |
624 Description | |
625 </th> | |
626 </tr> | |
627 | |
628 <tr> | |
629 <td> | |
630 name | |
631 </td> | |
632 <td> | |
633 name of this class | |
634 </td> | |
635 </tr> | |
636 | |
637 <tr> | |
638 <td> | |
639 superClass | |
640 </td> | |
641 <td> | |
642 class object representing super class of this class | |
643 </td> | |
644 </tr> | |
645 | |
646 <tr> | |
647 <td> | |
648 isArrayClass | |
649 </td> | |
650 <td> | |
651 boolean -- is the current class an array class? | |
652 </td> | |
653 </tr> | |
654 | |
655 <tr> | |
656 <td> | |
657 isStatic | |
658 </td> | |
659 <td> | |
660 boolean -- is the current class static or not | |
661 </td> | |
662 </tr> | |
663 | |
664 <tr> | |
665 <td> | |
666 isInterface | |
667 </td> | |
668 <td> | |
669 boolean -- is the current class an interface | |
670 </td> | |
671 </tr> | |
672 | |
673 <tr> | |
674 <td> | |
675 isAbstract | |
676 </td> | |
677 <td> | |
678 boolean -- is the current class abstract or not | |
679 </td> | |
680 </tr> | |
681 | |
682 <tr> | |
683 <td> | |
684 isProtected | |
685 </td> | |
686 <td> | |
687 boolean -- is the current class protected or not | |
688 </td> | |
689 </tr> | |
690 | |
691 <tr> | |
692 <td> | |
693 isPrivate | |
694 </td> | |
695 <td> | |
696 boolean -- is the current class private or not | |
697 </td> | |
698 </tr> | |
699 | |
700 <tr> | |
701 <td> | |
702 isPackagePrivate | |
703 </td> | |
704 <td> | |
705 boolean -- is the current class package private or not | |
706 </td> | |
707 </tr> | |
708 | |
709 <tr> | |
710 <td> | |
711 isSynthetic | |
712 </td> | |
713 <td> | |
714 boolean -- is the current class synthetic or not | |
715 </td> | |
716 </tr> | |
717 | |
718 <tr> | |
719 <td> | |
720 classLoader | |
721 </td> | |
722 <td> | |
723 object that represents ClassLoader object that loaded the current class | |
724 </td> | |
725 </tr> | |
726 | |
727 | |
728 <tr> | |
729 <td> | |
730 fields | |
731 </td> | |
732 <td> | |
733 array of static and instance fields of the current class | |
734 </td> | |
735 </tr> | |
736 | |
737 <tr> | |
738 <td> | |
739 protectionDomain | |
740 </td> | |
741 <td> | |
742 protection domain to which current class belongs | |
743 </td> | |
744 </tr> | |
745 | |
746 <tr> | |
747 <td> | |
748 isPublic | |
749 </td> | |
750 <td> | |
751 boolean -- is the current class public or not | |
752 </td> | |
753 </tr> | |
754 | |
755 <tr> | |
756 <td> | |
757 signers | |
758 </td> | |
759 <td> | |
760 array of signers for current class | |
761 </td> | |
762 </tr> | |
763 | |
764 <tr> | |
765 <td> | |
766 sourceFile | |
767 </td> | |
768 <td> | |
769 string -- name of the source file for current class | |
770 </td> | |
771 </tr> | |
772 | |
773 <tr> | |
774 <td> | |
775 interfaces | |
776 </td> | |
777 <td> | |
778 array -- interfaces implemented by current class | |
779 </td> | |
780 </tr> | |
781 | |
782 <tr> | |
783 <td> | |
784 isStrict | |
785 </td> | |
786 <td> | |
787 boolean -- is the current class strictfp or not | |
788 </td> | |
789 </tr> | |
790 | |
791 <tr> | |
792 <td> | |
793 methods | |
794 </td> | |
795 <td> | |
796 array of methods (static and instance) of the current class | |
797 </td> | |
798 </tr> | |
799 | |
800 | |
801 <tr> | |
802 <td> | |
803 isFinal | |
804 </td> | |
805 <td> | |
806 boolean -- is the current class final or not | |
807 </td> | |
808 </tr> | |
809 | |
810 <tr> | |
811 <td> | |
812 statics | |
813 </td> | |
814 <td> | |
815 name-value pairs (JavaScript associate array) of static fields of the current class | |
816 </td> | |
817 </tr> | |
818 </table> | |
819 | |
820 <h3>field object</h3> | |
821 <p> | |
822 field represents a static or instance field of some class in debuggee | |
823 </p> | |
824 | |
825 <table border="1"> | |
826 <tr> | |
827 <th> | |
828 Property name | |
829 </th> | |
830 <th> | |
831 Description | |
832 </th> | |
833 </tr> | |
834 | |
835 <tr> | |
836 <td> | |
837 isStatic | |
838 </td> | |
839 <td> | |
840 boolean -- is this field a static field? | |
841 </td> | |
842 </tr> | |
843 | |
844 <tr> | |
845 <td> | |
846 holder | |
847 </td> | |
848 <td> | |
849 class that owns this field | |
850 </td> | |
851 </tr> | |
852 | |
853 <tr> | |
854 <td> | |
855 signature | |
856 </td> | |
857 <td> | |
858 string signature of this field | |
859 </td> | |
860 </tr> | |
861 | |
862 <tr> | |
863 <td> | |
864 isProtected | |
865 </td> | |
866 <td> | |
867 boolean - is this field a protected field or not? | |
868 </td> | |
869 </tr> | |
870 | |
871 <tr> | |
872 <td> | |
873 isPrivate | |
874 </td> | |
875 <td> | |
876 boolean - is this field a private field or not? | |
877 </td> | |
878 </tr> | |
879 | |
880 <tr> | |
881 <td> | |
882 isSynthetic | |
883 </td> | |
884 <td> | |
885 boolean - is this javac generated synthetic field or not? | |
886 </td> | |
887 </tr> | |
888 | |
889 <tr> | |
890 <td> | |
891 isPackagePrivate | |
892 </td> | |
893 <td> | |
894 boolean - is this field a package private field or not? | |
895 </td> | |
896 </tr> | |
897 | |
898 <tr> | |
899 <td> | |
900 isTransient | |
901 </td> | |
902 <td> | |
903 boolean - is this field a transient field or not? | |
904 </td> | |
905 </tr> | |
906 | |
907 <tr> | |
908 <td> | |
909 isFinal | |
910 </td> | |
911 <td> | |
912 boolean - is this field final or not? | |
913 </td> | |
914 </tr> | |
915 | |
916 <tr> | |
917 <td> | |
918 name | |
919 </td> | |
920 <td> | |
921 string - name of this field | |
922 </td> | |
923 </tr> | |
924 | |
925 <tr> | |
926 <td> | |
927 isPublic | |
928 </td> | |
929 <td> | |
930 boolean - is this field public or not? | |
931 </td> | |
932 </tr> | |
933 </table> | |
934 | |
935 <h3>Initialization Script</h3> | |
936 <p> | |
937 jsdb engine looks for initialization script file named <b>jsdb.js</b> in user's home directory. If found, it loads just after attaching to debuggee but before printing prompt for user's input. User can assume that s/he can access debuggee VM | |
938 state during initialization script. | |
939 </p> | |
940 | |
941 <h3>Sample scripts</h3> | |
942 | |
943 Semantics and knowledge of application classes (for eg. AppServer's classes) would be needed to create app specific | |
944 scripts. The following script samples are app-independent and provide a flavour of kind of scripts that can be written. | |
945 | |
946 <h4>Script to print system properties of JVM</h4> | |
947 | |
948 <pre> | |
949 <code> | |
950 jvm.sysProps.toString() | |
951 </code> | |
952 </pre> | |
953 | |
954 <h4>Script to print JVM command line flags</h4> | |
955 <pre> | |
956 <code> | |
957 jvm.flags.toString() | |
958 </code> | |
959 </pre> | |
960 | |
961 | |
962 <h4>Script to print class-wise histogram of objects</h4> | |
963 | |
964 <pre> | |
965 <code> | |
966 | |
967 // associate array to hold histogram | |
968 var histo; | |
969 function func(obj) { | |
970 var classname = classof(obj).name; | |
971 if (histo[classname] == undefined) { | |
972 // first time we are visiting this class type | |
973 histo[classname] = 1; | |
974 } else { | |
975 histo[classname]++; | |
976 } | |
977 } | |
978 | |
979 // iterate through java heap calling 'func' for each object | |
980 jvm.heap.forEachObject(func); | |
981 | |
982 // print the histogram | |
983 for (i in histo) { | |
984 println('number of instances of ', i, ' = ', histo[i]); | |
985 } | |
986 | |
987 </code> | |
988 </pre> | |
989 | |
990 <h4>Script to print stack trace of all Java threads</h4> | |
991 | |
992 <pre> | |
993 <code> | |
994 | |
995 function printStackTrace(t) { | |
996 println(t.name); | |
997 println(''); | |
998 for (i in t.frames) { | |
999 println(t.frames[i]); | |
1000 } | |
1001 println(''); | |
1002 } | |
1003 | |
1004 // walk through the list of threads and call printStackTrace | |
1005 // for each thread | |
1006 for (o in jvm.threads) { | |
1007 printStackTrace(jvm.threads[o]); | |
1008 } | |
1009 | |
1010 | |
1011 </code> | |
1012 </pre> | |
1013 | |
1014 | |
1015 <h4>Script to re-construct .class files for all non-bootstrap classes</h4> | |
1016 | |
1017 <pre> | |
1018 <code> | |
1019 | |
1020 function dump(cl) { | |
1021 if (!cl.isArrayClass && cl.classLoader != null) { | |
1022 // not an array class and a non-bootstrap class | |
1023 // create .class files in e:\tmp dir | |
1024 dumpClass(cl, "e:\\tmp); | |
1025 } else { | |
1026 println("skipping bootstrap class ", cl.name); | |
1027 } | |
1028 } | |
1029 | |
1030 // walk thru heap and call callback for each java.lang.Class instance | |
1031 jvm.heap.forEachObject(dump, "java.lang.Class"); | |
1032 </code> | |
1033 </pre> | |
1034 | |
1035 <h4>Script to print paths of all java.io.File's currently accessed</h4> | |
1036 | |
1037 <pre> | |
1038 <code> | |
1039 | |
1040 function printFile(f) { | |
1041 // construct a mirror java.io.File here and | |
1042 // print absolute path here | |
1043 println(mirror(f).getAbsolutePath()); | |
1044 } | |
1045 | |
1046 jvm.heap.forEachObject(printFile, "java.io.File"); | |
1047 | |
1048 </code> | |
1049 </pre> | |
1050 | |
1051 <h4>Script to print static fields of java.lang.Thread class</h4> | |
1052 <pre> | |
1053 <code> | |
1054 | |
1055 var threadClass = classof("java.lang.Thread"); | |
1056 for (i in threadClass.statics) { | |
1057 println(i, '=', threadClass.statics[i]); | |
1058 } | |
1059 | |
1060 </code> | |
1061 </pre> | |
1062 | |
1063 <h3>Low level interface (VM State)</h3> | |
1064 | |
1065 <p> | |
1066 Low level jsdb interface works by <a href="http://www.mozilla.org/rhino/ScriptingJava.html">JavaScript-to-Java (previously known as "LiveConnect") | |
1067 interface</a> provided by Rhino JavaScript engine. | |
1068 </p> | |
1069 | |
1070 <h2>sapkg object</h2> | |
1071 <p> | |
1072 This object provides short names for SA package names. For eg. instead of writing | |
1073 Packages.sun.jvm.hotspot.memory, we can write sapkg.memory. | |
1074 </p> | |
1075 | |
1076 <h2>sa object</h2> | |
1077 <p> | |
1078 This object contains all SA singleton objects such as VM, Universe, SymbolTable, | |
1079 SystemDictionary, ObjectHeap, CollectedHeap, Debugger, CDebugger (if available), | |
1080 Interpreter, TypeDataBase and Threads. For eg. to access SymbolTable of Java debuggee, | |
1081 we can use sa.symbolTable. User can execute the following code to get fields of this object. | |
1082 </p> | |
1083 <pre> | |
1084 <code> | |
1085 for (i in sa) { | |
1086 println(i); | |
1087 } | |
1088 </code> | |
1089 </pre> | |
1090 | |
1091 <h4>Heap Iterators</h4> | |
1092 <dl> | |
1093 <dt>forEachOop(callback)</dt> | |
1094 <dd>calls a callback function for each Oop in Java heap</dd> | |
1095 <dt>forEachOopOfKlass(callback, klass, [includeSubtypes])</dt> | |
1096 <dd>calls a callback function for each Oop of a give Klass type | |
1097 Optinally, third argument can specify whether to include subtype Oops | |
1098 or not. | |
1099 </dd> | |
1100 </dl> | |
1101 | |
1102 <h4>System Dictionary Access</h4> | |
1103 <dl> | |
1104 <dt>forEachKlass(callback)</dt> | |
1105 <dd>calls a callback function for each Klass in Java heap</dd> | |
1106 <dt>forEachKlassAndLoader(callback)</dt> | |
1107 <dd> | |
1108 calls callback with Klass and initiating loader (Oop) for System dictionary | |
1109 entry. | |
1110 </dd> | |
1111 <dt>forEachPrimArrayKlass(callback)</dt> | |
1112 <dd> | |
1113 calls callback with Klass and initiating loader (Oop) for each | |
1114 primitive array Klass in the system. | |
1115 </dd> | |
1116 <dt>findInstanceKlass(name)</dt> | |
1117 <dd> | |
1118 finds the first instance klass with given name from System dictionary | |
1119 </dd> | |
1120 </dl> | |
1121 | |
1122 <h4>Thread, Frame Iterators</h4> | |
1123 <dl> | |
1124 <dt>forEachJavaThread(callback)</dt> | |
1125 <dd>calls callback for each Java Thread</dd> | |
1126 <dt>forEachFrame(javaThread, callback)</dt> | |
1127 <dd>calls callback for each Frame of a given JavaThread</dd> | |
1128 <dt>forEachVFrame(javaThread, callback)</dt> | |
1129 <dd>calls callback for each JavaVFrame of a given JavaThread</dd> | |
1130 <dt>forEachThread(callback)</dt> | |
1131 <dd>calls callback for each (native) ThreadProxy (obtained by CDebugger.getThreadList) | |
1132 </dd> | |
1133 <dt>forEachCFrame(threadProxy, callback)</dt> | |
1134 <dd> | |
1135 calls callback for each CFrame of a given ThreadProxy object | |
1136 </dd> | |
1137 </dl> | |
1138 | |
1139 <h4>Code blobs, Interpreter codelets</h4> | |
1140 <dl> | |
1141 <dt>forEachCodeBlob(callback)</dt> | |
1142 <dd> | |
1143 calls callback with each code blob in code cache | |
1144 </dd> | |
1145 <dt>findCodeBlob(address)</dt> | |
1146 <dd> | |
1147 finds the code blob, if any, that contains the given address. | |
1148 Returns null, on failure. | |
1149 </dd> | |
1150 <dt>findNMethod(address)</dt> | |
1151 <dd> | |
1152 finds the NMethod that contains given address. | |
1153 </dd> | |
1154 <dt>pcDescAt(addr)</dt> | |
1155 <dd> | |
1156 returns PCDesc at given address or null. | |
1157 </dd> | |
1158 <dt>forEachInterpCodelet(callbacl)</dt> | |
1159 <dd> | |
1160 calls callback with each Interpreter codelet | |
1161 </dd> | |
1162 </dl> | |
1163 | |
1164 <h4>VM structs, constants</h4> | |
1165 <dl> | |
1166 <dt>forEachType(callback)</dt> | |
1167 <dd> | |
1168 calls callback for each Type in VM's type database | |
1169 </dd> | |
1170 <dt>forEachVMIntConst(callback)</dt> | |
1171 <dd> | |
1172 calls callback for each named integer constant. passes name | |
1173 as argument. | |
1174 </dd> | |
1175 <dt>forEachVMLongConst(callback)</dt> | |
1176 <dd> | |
1177 calls callback for each named long constant. passes name | |
1178 as argument. | |
1179 </dd> | |
1180 <dt>findVMType(name)</dt> | |
1181 <dd> | |
1182 finds a VM type by name. returns null if no known Type of given name | |
1183 exists in type database. | |
1184 </dd> | |
1185 <dt>findVMIntConst(name)</dt> | |
1186 <dd> | |
1187 finds an integer constant in type data base by name. | |
1188 </dd> | |
1189 <dt>findVMLongConst(name)</dt> | |
1190 <dd> | |
1191 finds an long constant in type data base by name. | |
1192 </dd> | |
1193 <dt>vmTypeof(addr)</dt> | |
1194 <dd> | |
1195 returns VM type of object at 'addr' if any. Else, returns null. | |
1196 </dd> | |
1197 <dt>isOfVMType(addr, type)</dt> | |
1198 <dd> | |
1199 returns whether object at 'addr' is of VM type 'type' or not. | |
1200 </dd> | |
1201 <dt>printVMType(type, addr)</dt> | |
1202 <dd> | |
1203 prints 'addr' as VM object of type 'type' | |
1204 </dd> | |
1205 <dt>print<i>XXX</i>(addr)</dt> | |
1206 <dd> | |
1207 For each VM type, these functions are defined. For eg. there is printUniverse, | |
1208 printSystemDictionary etc. are available. Without 'addr' being passed static fields are printed. With 'addr' param being passed, instance fields are printed. | |
1209 </dd> | |
1210 </dl> | |
1211 | |
1212 <h4>Low level debugger facilities</h4> | |
1213 <dl> | |
1214 <dt>num2addr(number)</dt> | |
1215 <dd> | |
1216 converts a (long) number to SA Address instance | |
1217 </dd> | |
1218 <dt>str2addr(string)</dt> | |
1219 <dd> | |
1220 converts a given hex string to SA Address instance | |
1221 </dd> | |
1222 <dt>any2addr(any)</dt> | |
1223 <dd> | |
1224 Takes a number or a string or an Address and returns | |
1225 an Address instance. For other types, returns 'undefined' | |
1226 </dd> | |
1227 <dt>addr2str(addr)</dt> | |
1228 <dd> | |
1229 converts a given Address instance to a hex string | |
1230 </dd> | |
1231 <dt>addr2num(addr)</dt> | |
1232 <dd> | |
1233 converts a given Address instance to a (long) number | |
1234 </dd> | |
1235 <dt>sym2addr(library, symbol)</dt> | |
1236 <dd> | |
1237 returns Address of a given symbol in a given library (shared object or DLL) | |
1238 Example: sym2addr('jvm.dll', 'JNI_CreateJavaVM') | |
1239 <dt>addr2sym(addr)</dt> | |
1240 <dd> | |
1241 Returns nearest symbol to a given address (if any). If no such symbol is found, | |
1242 returns the given address as a string. | |
1243 </dd> | |
1244 <dt>readBytesAt(addr, num)</dt> | |
1245 <dd> | |
1246 returns 'num' bytes at 'addr' as a Java byte[] | |
1247 </dd> | |
1248 <dt>readWordsAt(addr, num)</dt> | |
1249 <dd> | |
1250 returns 'num' words at 'addr' as a Java long[] | |
1251 </dd> | |
1252 <dt>readCStrAt(addr)</dt> | |
1253 <dd> | |
1254 returns 'C' String at given address | |
1255 </dd> | |
1256 <dt>readCStrLen(addr)</dt> | |
1257 <dd> | |
1258 returns the length of the 'C' String at given address | |
1259 </dd> | |
1260 <dt>readRegs(threadProxy)</dt> | |
1261 <dd> | |
1262 returns register set (of Thread Context) of a given thread specified | |
1263 by threadProxy. return value is an associate array having name-value pairs | |
1264 of registers. | |
1265 </dd> | |
1266 <dt>regs(threadProxy)</dt> | |
1267 <dd> | |
1268 prints register set of a given thread. | |
1269 </dd> | |
1270 <dt>mem(addr, [num])</dt> | |
1271 <dd> | |
1272 prints 'num' words (address size) at 'addr'. Prints nearest symbol for address, if found. | |
1273 </dd> | |
1274 <dt>dis(addr, [num])</dt> | |
1275 <dd>prints native code disassembly of 'num' bytes at given address 'addr'. | |
1276 Default value of 'num' is 4. This automatically detects whether the given address | |
1277 inside a nmethod. If so, it prints safepoint info, entry points , method signature etc. | |
1278 of the nmethod. | |
1279 </dd> | |
1280 <dt>jdis(method [or addr])</dt> | |
1281 <dd> | |
1282 prints Java bytecode disassembly for given method Oop or address of a method Oop. | |
1283 </dd> | |
1284 <dt>nmethoddis(nmethod)</dt> | |
1285 <dd> | |
1286 prints disassembly of given nmethod object. Note that you don't have to call this directly | |
1287 instead use 'dis'. | |
1288 </dd> | |
1289 <dt>where</dt> | |
1290 <dd> | |
1291 prints Java stack trace for all Java threads | |
1292 </dd> | |
1293 </dl> | |
1294 | |
1295 <h4>Miscellaneous</h4> | |
1296 <dl> | |
1297 <dt>addr2oop(addr)</dt> | |
1298 <dd> | |
1299 converts a given address to a Oop object | |
1300 </dd> | |
1301 <dt>oop2addr(oop)</dt> | |
1302 <dd> | |
1303 returns address of a given Oop object | |
1304 </dd> | |
1305 <dt>isOfVMType(addr, type)</dt> | |
1306 <dd> | |
1307 returns whether the given 'addr' points to a (C++) VM object of specified | |
1308 type. type may be specified by SA Type object or string name of the type. | |
1309 </dd> | |
1310 <dt>newVMObject(addr)</dt> | |
1311 <dd> | |
1312 returns instance of SA object for a given address (similar to SA VirtualConstructor | |
1313 interface). | |
1314 </dd> | |
1315 <dt>vmobj2addr(vmobject)</dt> | |
1316 <dd> | |
1317 returns Address represented by a given SA VMObject | |
1318 </dd> | |
1319 <dt>addr2vmobj(addr)</dt> | |
1320 <dd>same as newVMObject(addr)</dd> | |
1321 <dt>whatis(addr)</dt> | |
1322 <dd> | |
1323 returns string description of given address (using SA FindPointer and guess type API). | |
1324 <dt>isOop(addr)</dt> | |
1325 <dd> | |
1326 returns whether a given address is a valid Oop address or not | |
1327 </dd> | |
1328 </dl> | |
1329 | |
1330 <h4>Moving b/w jsdb low level and high level interfaces</h4> | |
1331 | |
1332 <p> | |
1333 Java objects of debuggee are represented by different script wrappers in high level | |
1334 interface. In the low-level interface these are instances of SA Oop class or its' | |
1335 subclass. To move b/w low-level and high-level interfaces the following functions may | |
1336 be used | |
1337 </p> | |
1338 <dl> | |
1339 <dt>oop2obj(oop)</dt> | |
1340 <dd> | |
1341 converts a given Oop object to a high-level wrapper object | |
1342 </dd> | |
1343 <dt>obj2oop(obj)</dt> | |
1344 <dd> | |
1345 converts a jsdb high level wrapper to underlying Oop instance | |
1346 </dd> | |
1347 </dl> | |
1348 | |
1349 <h3>JavaScript tips</h3> | |
1350 | |
1351 <ul> | |
1352 <li>to know properties, functions of any object, use the script | |
1353 <pre> | |
1354 <core> | |
1355 for(i in object) { println(i); } | |
1356 </code> | |
1357 </pre> | |
1358 <li>to view the source code of any function, just type the name of | |
1359 function in jsdb prompt | |
1360 <li>to view global functions, properties, run | |
1361 <pre> | |
1362 <code> | |
1363 for(i in this) { println(i); } | |
1364 </code> | |
1365 </pre> | |
1366 </ul> | |
1367 | |
1368 </body> | |
1369 </html> |