[
https://issues.apache.org/activemq/browse/AMQ-1480?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=40994#action_40994
]
Patrick Stekovic commented on AMQ-1480:
---------------------------------------
Lets assume we want to consume one message from a queue that contains two
messages, using ActiveMQ's REST Interface with a HTTP GET request.
Looking at MessageServlet.java in the activemq-web module, the method doGet()
calls the method doMessages() :
{noformat}
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doMessages(request, response, -1);
}
{noformat}
As we are not using AJAX, the variable maxMessages gets the value 1:
{noformat}
protected void doMessages(HttpServletRequest request, HttpServletResponse
response, int maxMessages) throws ServletException, IOException {
...
boolean ajax = isRicoAjax(request);
if (!ajax) {
maxMessages = 1;
}
...
}
{noformat}
In the synchronized()-block, we are consuming the first message in the queue:
{noformat}
synchronized(consumer){
...
// Look for any available messages
message = consumer.receiveNoWait();
...
}
{noformat}
Then, as message is not null and maxMessages has the value 1, we are entering
the while-block:
{noformat}
// send a response for each available message (up to max
// messages)
while ((maxMessages < 0 || messages < maxMessages) && message !=
null) {
// System.err.println("message["+messages+"]="+message);
if (ajax) {
writer.print("<response type='object' id='");
writer.print(request.getParameter("id"));
writer.println("'>");
} else {
// only ever 1 message for non ajax!
setResponseHeaders(response, message);
}
writeMessageResponse(writer, message);
if (ajax) {
writer.println("</response>");
}
// look for next message
message = consumer.receiveNoWait();
messages++;
}
{noformat}
And here sitts the bug in my opinion. The method consumer.receiveNoWait() is
called a second time. That means, our second message gets deleted from the
queue.
So I put the receiveNoWait() call in an if(ajax) block:
{noformat}
if (ajax){
// look for next message
message = consumer.receiveNoWait();
}
{noformat}
This works fine for me.
> Problem with REST
> -----------------
>
> Key: AMQ-1480
> URL: https://issues.apache.org/activemq/browse/AMQ-1480
> Project: ActiveMQ
> Issue Type: Bug
> Affects Versions: 5.0.0
> Environment: linux / jdk 1.5.0
> Reporter: Patrick Stekovic
> Attachments: patch.txt
>
>
> Every time I read one message (with REST/GET) from a queue with more than 1
> message, two messages are deleted.
--
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.
