自己的JVM自己救: 解救 OOM 實務經驗談 (JCConf 2015)
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The document discusses garbage collection and object graphs. It lists objects and their outgoing references, showing how objects are connected and retained in memory. It also covers using Log4j in web applications and ensuring proper cleanup of logging resources during undeployment.
![/* */ public abstract class ItemFactory
/* */ implements Constants
/* */ {
/* */ protected static Logger a;
/* 45 */ public Map b = null;
/* */ public static int c;
/* */ private static String[] A;
/* */
/* */ protected ItemFactory()
/* */ {
/* 51 */ this.b = Collections.synchronizedMap(new HashMap());
/* 52 */ if ((ItemBean.d) || (a == null)) {
/* 53 */ a = Logger.getLogger(A[2]);
/* */ }
/* */ }
Bad news: It is obfuscated (混淆)
Can’t decompile, rewrite, and compile …](https://image.slidesharecdn.com/jcconf2015oomleon-151205083612-lva1-app6891/85/JVM-OOM-JCConf-2015-70-320.jpg)
自己的JVM自己救: 解救 OOM 實務經驗談 (JCConf 2015)
- 1. #JCConf
- 3. • • • •
- 6. • • • •
- 7. #JCConf
- 13. 13
- 16. #JCConf
- 19. • – • • – • • –
- 21. A B C D E F G H A and B are garbage collection roots, (GC roots) Leading Set Retained Set E E, G C C, D, E, F, G, H A, B A, B, C, D, E, F, G, H
- 23. A B C D E F G H
- 24. A B C D E F G H
- 26. A B C D E F G H
- 28. A B C D E F G H
- 29. #JCConf
- 33. Done
- 34. More Things…
- 37. oracle.jdbc.ScrollableResultSet → scrollStmt → sqlObject → sqlBytes → Copy → Value
- 49. • • • •
- 50. • • • •
- 51. #JCConf
- 52. • – • – •
- 60. Expand the node
- 62. Using Log4j 2 in Web Applications You must take particular care when using Log4j or any other logging framework within a Java EE web application. It's important for logging resources to be properly cleaned up (database connectionsclosed, files closed, etc.) when the container shuts down or the web application is undeployed. Because of the nature of class loaders within web applications, Log4j resources cannot be cleaned up through normalmeans. Log4j must be "started" when the web application deploys and "shut down" when the web application undeploys. How this works varies depending on whether your application is a Servlet 3.0 or newer or Servlet 2.5 web application. In either case, you'll need to add the log4j-web module to your deployment as detailed in the Maven, Ivy, and Gradle Artifacts manualpage. To avoid problems the Log4j shutdown hook will automatically be disabled when the log4j-web jar is included.
- 65. •
- 67. • • – – • –
- 68. #JCConf
- 69. • • • • • •
- 70. /* */ public abstract class ItemFactory /* */ implements Constants /* */ { /* */ protected static Logger a; /* 45 */ public Map b = null; /* */ public static int c; /* */ private static String[] A; /* */ /* */ protected ItemFactory() /* */ { /* 51 */ this.b = Collections.synchronizedMap(new HashMap()); /* 52 */ if ((ItemBean.d) || (a == null)) { /* 53 */ a = Logger.getLogger(A[2]); /* */ } /* */ } Bad news: It is obfuscated (混淆) Can’t decompile, rewrite, and compile …
- 71. • public aspect ItemFactoryAop { private final static int DEFAULT_CACHE_SIZE = 100000; after() : execution(workflow.ItemFactory.new()) { ((ItemFactory)thisJoinPoint.getThis()).b = Collections.synchronizedMap( new cache.LruCache(DEFAULT_CACHE_SIZE)); } }
- 72. • – • – • •
- 73. #JCConf
- 74. • • • • •
- 78. • • • –
- 79. #JCConf
- 80. • • • •
- 81. #JCConf
- 82. MayYour JVM Live Long and Prosper 生生不息、繁榮昌盛