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  1. JDK
  2. JDK-6717784

Memory leak in LogManager when used with subclassed resource bundle

    Details

    • Type: Bug
    • Status: Closed
    • Priority: P4
    • Resolution: Duplicate
    • Affects Version/s: 6
    • Fix Version/s: None
    • Component/s: core-libs
    • Labels:

      Description

      FULL PRODUCT VERSION :
      java version "1.6.0_06"
      Java(TM) SE Runtime Environment (build 1.6.0_06-b02)
      Java HotSpot(TM) Client VM (build 10.0-b22, mixed mode, sharing)

      ADDITIONAL OS VERSION INFORMATION :
      Microsoft Windows [Version 5.2.3790]

      A DESCRIPTION OF THE PROBLEM :
      LogManager retains strong references to Loggers.
      Logger retains strong reference to ResourceBundle.
      When ResourceBundle is subclassed and loaded by a custom class loader, this results in a memory leak because custom class loader is strongly reachable from LogManager.
      In environments with dynamic class loaders (such as J2EE) this often leads to infamous OutOfMemoryError: PermGen space exception.
      The problem was discovered with Glassfish v2 and Apache MyFaces Trinidad 1.2.8. Trinidad subclasses ListResourceBundle to provide log messages localization.


      STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
      Execute the provided test case.


      EXPECTED VERSUS ACTUAL BEHAVIOR :
      EXPECTED -
      Both test methods should succeed.
      ACTUAL -
      Test method test1() fails.
      Test method test2() succeeds.

      REPRODUCIBILITY :
      This bug can be reproduced always.

      ---------- BEGIN SOURCE ----------

      ======= MyClassLoader.java =======
      import java.net.URLClassLoader;
      import java.net.URL;

      public class MyClassLoader extends URLClassLoader
      {
          public MyClassLoader(URL[] urls)
          {
              super(urls, null);
          }

          public static MyClassLoader create()
          {
              URLClassLoader defaultLoader = (URLClassLoader) Thread.currentThread().getContextClassLoader();
              URL[] classpath = defaultLoader.getURLs();
              return new MyClassLoader(classpath);
          }
      }

      ======= MyLogger.java =======
      import java.util.logging.Logger;

      public class MyLogger extends Logger
      {
          public MyLogger(String name, String resourceBundleName)
          {
              super(name, resourceBundleName);
          }
      }

      ======= MyResourceBundle1.java =======
      import java.util.ListResourceBundle;

      public class MyResourceBundle1 extends ListResourceBundle
      {
          protected Object[][] getContents()
          {
              return new Object[][]
                      {
                              {"test.key", "test value 1"},
                      };
          }
      }

      ======= Test1.java =======
      import static junit.framework.Assert.*;
      import org.junit.Test;

      import java.lang.ref.WeakReference;
      import java.lang.reflect.Field;
      import java.util.ResourceBundle;
      import java.util.logging.LogManager;
      import java.util.logging.Logger;

      public class Test1
      {
          @Test
          public void test1() throws Exception
          {
              // init log manager in default class loader
              LogManager.getLogManager();

              ClassLoader myClassLoader = MyClassLoader.create();
              createLoggerWithTempClassLoader(myClassLoader, "test1", "MyResourceBundle1");

              assertSame(myClassLoader, bundleClassLoader(Logger.getLogger("test1").getResourceBundle()));
              assertEquals("test value 1", Logger.getLogger("test1").getResourceBundle().getString("test.key"));

              myClassLoader = null;
              System.gc();

              assertNull(bundleClassLoader(Logger.getLogger("test1").getResourceBundle()));
          }

          @Test
          public void test2() throws Exception
          {
              // init log manager in default class loader
              LogManager.getLogManager();

              ClassLoader myClassLoader = MyClassLoader.create();
              createLoggerWithTempClassLoader(myClassLoader, "test2", "MyResourceBundle2");

              assertSame(myClassLoader, bundleClassLoader(Logger.getLogger("test2").getResourceBundle()));
              assertEquals("test value 2", Logger.getLogger("test2").getResourceBundle().getString("test.key"));

              myClassLoader = null;
              System.gc();

              assertNull(bundleClassLoader(Logger.getLogger("test2").getResourceBundle()));
          }

          private void createLoggerWithTempClassLoader(ClassLoader myClassLoader, String loggerName, String bundleName)
          {
              ClassLoader defaultLoader = Thread.currentThread().getContextClassLoader();
              Thread.currentThread().setContextClassLoader(myClassLoader);
              MyLogger logger = new MyLogger(loggerName, bundleName);
              assertTrue(LogManager.getLogManager().addLogger(logger));
              Thread.currentThread().setContextClassLoader(defaultLoader);
          }

          private ClassLoader bundleClassLoader(ResourceBundle resourceBundle) throws Exception
          {
              Object cacheKey = getFieldValue(ResourceBundle.class, resourceBundle, "cacheKey");
              WeakReference loaderRef = (WeakReference) getFieldValue(cacheKey, "loaderRef");
              return (ClassLoader) loaderRef.get();
          }

          private Object getFieldValue(Object obj, String fieldName) throws Exception
          {
              return getFieldValue(obj.getClass(), obj, fieldName);
          }

          private Object getFieldValue(Class clazz, Object obj, String fieldName) throws Exception
          {
              Field field = clazz.getDeclaredField(fieldName);
              field.setAccessible(true);
              return field.get(obj);
          }
      }


      ---------- END SOURCE ----------

      CUSTOMER SUBMITTED WORKAROUND :
      Do not use ResourceBundle subclassing with Java Logging API.

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              • Assignee:
                Unassigned
                Reporter:
                ndcosta Nelson Dcosta (Inactive)
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                • Created:
                  Updated:
                  Resolved:
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