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https://issues.apache.org/activemq/browse/AMQ-1254?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_39495
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solprovider commented on AMQ-1254:
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The reason amq is using this poor design is a programmer did not read the docs
for the System class. ActiveMQ contains code that will break if
System.Properties contains elements that cannot be cast to String.
To fix this:
1. Discard function getVmLockSet(). The locks cannot use a Set.
2. Change lock() and unlock() to this code:
{code:title=Good Locking|borderStyle=solid}
private synchronized void lock() throws IOException {
if (!disableLocking && directory != null && lock == null) {
String key = getClass().getName() + ".lock." +
directory.getCanonicalPath().replaceAll(":/\\\\", ".");
String property = System.getProperty(key);
if ((null == property) || ("" == property)) {
if (!brokenFileLock) {
lock = rootIndexManager.getLock();
if (lock == null) {
throw new StoreLockedExcpetion("Kaha
Store " + directory.getName() + " is already opened by another application");
} else
System.setProperty(key, "LOCK");
//Could store datetime of lock.
}
} else { //already locked
throw new StoreLockedExcpetion("Kaha Store " +
directory.getName() + " is already opened by this application.");
}
}
}
private synchronized void unlock() throws IOException {
if (!disableLocking && (null != directory) && (null != lock)) {
String key = getClass().getName() + ".lock." +
directory.getCanonicalPath().replaceAll(":/\\\\", ".");
if (null != System.getProperty(key))
System.setProperty(key, "");
if (lock.isValid()) {
lock.release();
}
lock = null;
}
}
{code}
This should be faster since we are not retrieving a Set<String>. This should
use less memory since we do not have the overhead of one Set<String>. This does
not violate System.Properties by bypassing its functions to use the parent
HashMap functions.
Warning: I am not set up to work with Java 1.5 (required by this class) so this
needs to be tested.
> Kaha Store puts a non-string into System properties
> ---------------------------------------------------
>
> Key: AMQ-1254
> URL: https://issues.apache.org/activemq/browse/AMQ-1254
> Project: ActiveMQ
> Issue Type: Bug
> Affects Versions: 4.1.2
> Reporter: David Jencks
> Attachments: Kaha-Store.patch
>
>
> KahaStore puts a hashmap into SystemProperties, which causes problems with
> programs that expect only strings as properties. In particular some versions
> of Hibernate assume all system properties are strings: this is causing
> difficulties running roller in geronimo 2.0
> Attached is a proposed solution. I have no idea how to test it. I get the
> same 7 failures and one error building amq with and without the change.
> The proposal stores the list of locked directories in a string and converts
> it back and forth to a map whenever it is accessed. I use a constant string
> as the vm-wide lock monitor formerly provided by the HashSet. According to
> the String javadoc constant strings are intern()ed and the same instance is
> provided in any classloader: this makes it suitable for a vm-wide lock
> monitor.
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