Memory cache using WEAK references can lead to memory leak
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Key: IBATIS-562
URL: https://issues.apache.org/jira/browse/IBATIS-562
Project: iBatis for Java
Issue Type: Bug
Components: SQL Maps
Affects Versions: 2.3.4
Environment: Hp NonStop H06.14 , NonStop Java 1.5.0_02 Ibatis build
2.3.4.726
Reporter: Alan Charley
Caching objects in memory using WEAK references will lead to memory leaks
because GC can occur on object, yet cache memory still has reference to object.
Since the key is present in the hashmap but the object being cached has been
destroyed, value returns as null indicating a cache miss. Then the object is
cached again, and again, and again. This causes the haspmap to grow until JVM
crashes with out of memory.
Code snippet below from MemoryCacheController.java
public Object getObject(CacheModel cacheModel, Object key) {
Object value = null;
Object ref = cache.get(key);
if (ref != null) {
if (ref instanceof StrongReference) {
value = ((StrongReference) ref).get();
} else if (ref instanceof SoftReference) {
value = ((SoftReference) ref).get();
} else if (ref instanceof WeakReference) {
value = ((WeakReference) ref).get();
}
}
/* AJC added this code to prevent memory leak if object key is in cached
list but value had been removed */
if (value == null) {
if (ref != null) {
cache.remove(key);
}
}
/* end of code added */
return value;
}
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