Description Flannan Lo 2011-09-23 15:21:43 EDT

Build Identifier: M20110210-1200

In this method, private void updateChildren(Widget widget, Object parent,
			Object[] elementChildren, boolean updateLabels), I am getting a SWTException when refreshing a tree viewer, it is not easily reproducible but I will try to describe what I have observed. I inspect the code and I found a place that may cause problems. IN the following snippet,

		// dispose of surplus items, optimizing for the case where elements have
		// been deleted but not reordered, or all elements have been removed.
		int numItemsToDispose = items.length - min;
		if (numItemsToDispose > 0) {
			CustomHashtable children = newHashtable(elementChildren.length * 2);
			for (int i = 0; i < elementChildren.length; i++) {
				Object elementChild = elementChildren[i];
				children.put(elementChild, elementChild);
			}
			int i = 0;
			while (numItemsToDispose > 0 && i < items.length) {
				Object data = items[i].getData();
				if (data == null || items.length - i <= numItemsToDispose || !children.containsKey(data)) {
					if (data != null) {
						disassociate(items[i]);
					}
					items[i].dispose();
					if (i + 1 < items.length) {
						// The components at positions i+1 through
						// items.length-1 in the source array are copied into
						// positions i through items.length-2
						System.arraycopy(items, i + 1, items, i, items.length - (i+1));
					}
					numItemsToDispose--;
				} else {
					i++;
				}
			}
		}

The line, System.arraycopy(items, i + 1, items, i, items.length - (i+1)), can cause problem. For example, when you currently have 17 items and need to dispose the last 5 items. The arraycopy method does not move the items up. Instead, it just copy the items at the end of the array to the item position where the item is disposed. So the length always stays at 17. It copies the reference (see screenshots) and so I end up having 3 same item in my array at position 15, 16, 17. Next time, when it processes item #15 and disposes it, the item at 15, 16, 17 are all disposed because it they are all referencing the same element. Then when the code do item.getData() on these items, I am getting a SWTException.

Reproducible: Sometimes

Steps to Reproduce:
I cannot reproduce this problem in Eclipse only, but I can reproduce the problem every time with my project in IBM Integration Developer. Let me know if you want to see this problem in IBM Integration Developer. If you want to reproduce the problem yourself, you need IBM Integration Developer, Monitor Toolkit and BPM Process Center Server Advanced 7.5.1. Let me know if you want to setup the environment.