Wow, someone responded to google-gson issue # 402[1]: Memory Leak in web
application; comment # 25, and shared the following, and this works in my
web app!
import com.google.gson.Gson;
import java.lang.ref.WeakReference;
import java.lang.reflect.Array;
import java.lang.reflect.Field;
class GSONThreadLocalImmolater {
public static void main(final String[] args) {
new Gson().toJson("blah");
immolate(); // should print 1
}
static void immolate() {
try {
int count = 0;
final Field threadLocalsField = Thread.class.
getDeclaredField("threadLocals");
threadLocalsField.setAccessible(true);
final Field inheritableThreadLocalsField = Thread.
class.getDeclaredField("inheritableThreadLocals");
inheritableThreadLocalsField.setAccessible(true);
for (final Thread thread : Thread.getAllStackTraces
().keySet()) {
count += clear(threadLocalsField.get(thread
));
count += clear(inheritableThreadLocalsField.
get(thread));
}
System.out.println("immolated " + count + " GSON
values in ThreadLocals");
} catch (final Exception e) {
throw new Error("die", e);
}
}
private static int clear(final Object threadLocalMap) throws
Exception {
if (threadLocalMap == null)
return 0;
int count = 0;
final Field tableField = threadLocalMap.getClass().
getDeclaredField("table");
tableField.setAccessible(true);
final Object table = tableField.get(threadLocalMap);
for (int i = 0, length = Array.getLength(table); i < length;
++i) {
final Object entry = Array.get(table, i);
if (entry != null) {
final Object threadLocal = ((WeakReference)
entry).get();
if (threadLocal != null && threadLocal.
getClass().getEnclosingClass() == Gson.class) {
Array.set(table, i, null);
++count;
}
}
}
return count;
}
}
[1] https://code.google.com/p/google-gson/issues/detail?id=402
On Tue, Dec 11, 2012 at 12:00 AM, Howard W. Smith, Jr. <
[email protected]> wrote:
> Please see exceptions below that usually occur when I shutdown TomEE (to
> deploy/drop a new WAR file). I am already using @PreDestroy on CDI
> @ApplicationScoped beanto stop other services. I think these exceptions are
> telling me that it might be best for me to do some type of stop-or-destroy
> Google Apss API as well. Please confirm. Thanks.
>
>
> SEVERE: The web application [/mcmsweb] appears to have started a thread
> named [Thread-59] but has failed to stop it. This is very likely to create
> a memory leak.
> Dec 10, 2012 11:16:12 PM org.apache.catalina.loader.WebappClassLoader
> clearReferencesThreads
> SEVERE: The web application [/mcmsweb] appears to have started a thread
> named [AWT-Windows] but has failed to stop it. This is very likely to
> create a memory leak.
> Dec 10, 2012 11:16:12 PM org.apache.catalina.loader.WebappClassLoader
> checkThreadLocalMapForLeaks
> SEVERE: The web application [/mcmsweb] created a ThreadLocal with key of
> type [com.google.api.client.util.escape.Platform$1] (value
> [com.google.api.client.util.escape.Platform$1@1757c6b]) and a value of
> type [char[]] (value [[C@3b9319]) but failed to remove it when the web
> application was stopped. Threads are going to be renewed over time to try
> and avoid a probable memory leak.
> Dec 10, 2012 11:16:12 PM org.apache.catalina.loader.WebappClassLoader
> checkThreadLocalMapForLeaks
> SEVERE: The web application [/mcmsweb] created a ThreadLocal with key of
> type [com.google.api.client.util.escape.Platform$1] (value
> [com.google.api.client.util.escape.Platform$1@1757c6b]) and a value of
> type [char[]] (value [[C@13656a2]) but failed to remove it when the web
> application was stopped. Threads are going to be renewed over time to try
> and avoid a probable memory leak.
> Dec 10, 2012 11:16:12 PM org.apache.catalina.loader.WebappClassLoader
> checkThreadLocalMapForLeaks
> SEVERE: The web application [/mcmsweb] created a ThreadLocal with key of
> type [com.google.api.client.util.escape.Platform$1] (value
> [com.google.api.client.util.escape.Platform$1@1757c6b]) and a value of
> type [char[]] (value [[C@71c1ff]) but failed to remove it when the web
> application was stopped. Threads are going to be renewed over time to try
> and avoid a probable memory leak.
> Dec 10, 2012 11:16:12 PM org.apache.catalina.loader.WebappClassLoader
> checkThreadLocalMapForLeaks
> SEVERE: The web application [/mcmsweb] created a ThreadLocal with key of
> type [com.google.api.client.util.escape.Platform$1] (value
> [com.google.api.client.util.escape.Platform$1@1757c6b]) and a value of
> type [char[]] (value [[C@77759b]) but failed to remove it when the web
> application was stopped. Threads are going to be renewed over time to try
> and avoid a probable memory leak.
> Dec 10, 2012 11:16:12 PM org.apache.catalina.loader.WebappClassLoader
> checkThreadLocalMapForLeaks
> SEVERE: The web application [/mcmsweb] created a ThreadLocal with key of
> type [com.google.gson.Gson$1] (value [com.google.gson.Gson$1@ca428a]) and
> a value of type [java.util.HashMap] (value [{}]) but failed to remove it
> when the web application was stopped. Threads are going to be renewed over
> time to try and avoid a probable memory leak.
> Dec 10, 2012 11:16:12 PM org.apache.catalina.loader.WebappClassLoader
> checkThreadLocalMapForLeaks
> SEVERE: The web application [/mcmsweb] created a ThreadLocal with key of
> type [com.google.api.client.util.escape.Platform$1] (value
> [com.google.api.client.util.escape.Platform$1@1757c6b]) and a value of
> type [char[]] (value [[C@d685eb]) but failed to remove it when the web
> application was stopped. Threads are going to be renewed over time to try
> and avoid a probable memory leak.
> Dec 10, 2012 11:16:12 PM org.apache.catalina.loader.WebappClassLoader
> checkThreadLocalMapForLeaks
> SEVERE: The web application [/mcmsweb] created a ThreadLocal with key of
> type [com.google.api.client.util.escape.Platform$1] (value
> [com.google.api.client.util.escape.Platform$1@1757c6b]) and a value of
> type [char[]] (value [[C@1f21c3f]) but failed to remove it when the web
> application was stopped. Threads are going to be renewed over time to try
> and avoid a probable memory leak.
> Dec 10, 2012 11:16:12 PM org.apache.catalina.loader.WebappClassLoader
> checkThreadLocalMapForLeaks
> SEVERE: The web application [/mcmsweb] created a ThreadLocal with key of
> type [com.google.api.client.util.escape.Platform$1] (value
> [com.google.api.client.util.escape.Platform$1@1757c6b]) and a value of
> type [char[]] (value [[C@1c7a6e]) but failed to remove it when the web
> application was stopped. Threads are going to be renewed over time to try
> and avoid a probable memory leak.
>
>
