https://sourceforge.net/p/beepcore-java/bugs/40/2005-11-23T23:25:14ZRecent changes to 40: removeSessionListener, get NullPointerExce2005-11-23T23:25:14Z2005-11-23T23:25:14ZPete Siemsenhttps://sourceforge.net/u/siemsen/https://sourceforge.net892f9d639d369da1c5eb0c76a38bdf2cb8cf76f2

<div class="markdown_content"><p>If you</p> <p>1. open a session<br /> 2. add a sessionlistener<br /> 3. remove the sessionListener<br /> 4. close the session</p> <p>...you'll get a NullPointerException.</p> <p>The problem is in SessionImpl.java, and affects both<br /> sessions and channels, which use similar code to<br /> maintain lists of listeners. For some reason, a<br /> list is maintained and an array is maintained<br /> containing the same information. The problem comes<br /> from this odd implementation (why not use just a<br /> List?).<br /> In removeSessionListener, the object is removed from<br /> the list, and then the list is converted to the array,<br /> but a zero-length List doesn't get converted to an<br /> empty array. From the docs for toArray():</p> <p>If the list fits in the specified array with room<br /> to spare (i.e., the array has more elements than<br /> the list), the element in the array immediately<br /> following the end of the collection is set to null.</p> <p>The above is always true in removeSessionListener,<br /> so the array gets one more element than the writer<br /> intended. Later, when, say, fireSessionTerminated<br /> is called, it tests for an array length of zero.<br /> The array has one (null) element, the test fails,<br /> the null is accessed, and a NullPointerException<br /> happens.</p> <p>I fixed this by changing the tests in the six fireXXX<br /> methods to make them check for a list size of zero<br /> instead of an array length of zero. It seems that<br /> this code and the corresponding add/remove methods<br /> would be better if Lists were used and the arrays<br /> were dropped.</p></div>