Adam Bien's Weblog

Unsynchronized access to java.util.WeakHashMap may cause …an endless loop. See method java.util.WeakHashMap#get:

public V get(Object key) {
        Object k = maskNull(key);
        int h = hash(k);
        Entry[] tab = getTable();
        int index = indexFor(h, tab.length);
        Entry e = tab[index];

        while (e != null) {
            if (e.hash == h && eq(k, e.get()))
                return e.value;
            e = e.next;
        }

        return null;
    }

Although it seems unlikely, it actually happens. One day we found a majority of worker threads stuck with the following stacktrace:

"httpSSLWorkerThread-32470-8"
java.lang.Thread.State: RUNNABLE
at java.util.WeakHashMap.get(WeakHashMap.java:355)
at javax.faces.component.UIComponentBase.populateDescriptorsMapIfNecessary(UIComponentBase.java:147)
at javax.faces.component.UIComponentBase.(UIComponentBase.java:142)
at javax.faces.component.UIOutput.(UIOutput.java:119)

See you at Java EE Workshops at MUC Airport (March 25th-28th)!

Posted at 07:24AM Oct 24, 2012 by Adam Bien in Real World Java EE Patterns - Rethinking Best Practices |  Comments[3]  | Views/Hits: 3288

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