在web开发中，我遇到了一个很严重的内存泄漏问题，困扰了我一段时间，但经常周折才在HPjmeter的帮助上找到了问题的根源，原来是Digest认证的问题，并且是tomcat的大bug. 现给大家介绍一下，希望大家也能从中受益。
发生问题的类就是DigestAuthenticator.java
里面有这么一句话：
// Updating the value in the no once hashtable 我个人看，这段代码是tomcat开发人员想处置的一段代码，但可能没有最终用，把这句代码就留下来了，但你可别小看它，它的意思就是往hashtable中加入一条数据，你的web应用如果有大量的digest认证连接就坏了，这段代码会往hashtable加入了很多垃圾数据，但没有代码往外清理，那这就是内存泄漏，我们的同仁说这是内存keep. 解决的办法也很简单就是把这句话注释掉。
nOnceTokens.put(nOnceValue, new Long(currentTime + nOnceTimeout));
列出下面tomcat对这个bug的解释（太可气了，人家才说这是p2的bug)
The DigestAuthenticator class contains a small but significant leak. In the
generateNOnce method, the
nOnceValue is inserted into a Hashtable with an expire time. This feature does
not appear to be fully
implemented and as a result the Hashtable "nOnceTokens" will continue to grow
un-bounded.
The short term solution to this problem is to remove the Hashtable insert since
it isn't apparently being
used.
Longer term, the host-expireTime-otherState tuple could be encoded in
client-opaque nOnceValue and
used across multiple TC5 instances.
generateNOnce method, the
nOnceValue is inserted into a Hashtable with an expire time. This feature does
not appear to be fully
implemented and as a result the Hashtable "nOnceTokens" will continue to grow
un-bounded.
The short term solution to this problem is to remove the Hashtable insert since
it isn't apparently being
used.
Longer term, the host-expireTime-otherState tuple could be encoded in
client-opaque nOnceValue and
used across multiple TC5 instances.
本文转自 tianjinhm 51CTO博客，原文链接:http://blog.51cto.com/hanmei/135378
