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https://issues.apache.org/jira/browse/AMQ-4938 

apply patch with cleanups
This commit is contained in:
Timothy Bish 2014-01-16 10:19:10 -05:00
parent e56c062f27
commit a2ede974b9
1 changed files with 140 additions and 71 deletions
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211
activemq-web/src/main/java/org/apache/activemq/web/MessageServlet.java
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@ -21,6 +21,7 @@ import java.io.IOException;
import java.io.PrintWriter;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.HashSet;
import javax.jms.Destination;
import javax.jms.JMSException;
@ -42,11 +43,18 @@ import org.slf4j.LoggerFactory;
/**
* A servlet for sending and receiving messages to/from JMS destinations using
* HTTP POST for sending and HTTP GET for receiving. <p/> You can specify the
* destination and whether it is a topic or queue via configuration details on
* the servlet or as request parameters. <p/> For reading messages you can
* specify a readTimeout parameter to determine how long the servlet should
* block for.
* HTTP POST for sending and HTTP GET for receiving.
* <p/>
* You can specify the destination and whether it is a topic or queue via
* configuration details on the servlet or as request parameters.
* <p/>
* For reading messages you can specify a readTimeout parameter to determine how
* long the servlet should block for.
*
* One thing to keep in mind with this solution - due to the nature of REST,
* there will always be a chance of losing messages. Consider what happens when
* a message is retrieved from the broker but the web call is interrupted before
* the client receives the message in the response - the message is lost.
*/
public class MessageServlet extends MessageServletSupport {
@ -59,12 +67,15 @@ public class MessageServlet extends MessageServletSupport {
private static final Logger LOG = LoggerFactory.getLogger(MessageServlet.class);
private final String readTimeoutParameter = "readTimeout";
private final String readTimeoutRequestAtt = "xamqReadDeadline";
private final String oneShotParameter = "oneShot";
private long defaultReadTimeout = -1;
private long maximumReadTimeout = 20000;
private long requestTimeout = 1000;
private String defaultContentType = "application/xml";
private final HashMap<String, WebClient> clients = new HashMap<String, WebClient>();
private final HashSet<MessageAvailableConsumer> activeConsumers = new HashSet<MessageAvailableConsumer>();
@Override
public void init() throws ServletException {
@ -144,7 +155,7 @@ public class MessageServlet extends MessageServletSupport {
}
/**
* Supports a HTTP DELETE to be equivlanent of consuming a singe message
* Supports a HTTP DELETE to be equivalent of consuming a singe message
* from a queue
*/
@Override
@ -153,7 +164,7 @@ public class MessageServlet extends MessageServletSupport {
}
/**
* Supports a HTTP DELETE to be equivlanent of consuming a singe message
* Supports a HTTP DELETE to be equivalent of consuming a singe message
* from a queue
*/
@Override
@ -170,69 +181,115 @@ public class MessageServlet extends MessageServletSupport {
* @throws IOException
*/
protected void doMessages(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
MessageAvailableConsumer consumer = null;
try {
WebClient client = getWebClient(request);
Destination destination = getDestination(client, request);
if (destination == null) {
throw new NoDestinationSuppliedException();
}
MessageAvailableConsumer consumer = (MessageAvailableConsumer)client.getConsumer(destination, request.getHeader(WebClient.selectorName));
Message message = null;
message = (Message)request.getAttribute("message");
if (message != null) {
// we're resuming continuation,
// so just write the message and return
writeResponse(request, response, message);
return;
consumer = (MessageAvailableConsumer) client.getConsumer(destination, request.getHeader(WebClient.selectorName));
Continuation continuation = ContinuationSupport.getContinuation(request);
// Don't allow concurrent use of the consumer. Do make sure to allow
// subsequent calls on continuation to use the consumer.
if (continuation.isInitial()) {
synchronized (activeConsumers) {
if (activeConsumers.contains(consumer)) {
throw new ServletException("Concurrent access to consumer is not supported");
} else {
activeConsumers.add(consumer);
}
}
}
Message message = null;
long deadline = getReadDeadline(request);
long timeout = deadline - System.currentTimeMillis();
// Set the message available listener *before* calling receive to eliminate any
// chance of a missed notification between the time receive() completes without
// a message and the time the listener is set.
synchronized (consumer) {
Listener listener = (Listener) consumer.getAvailableListener();
if (listener == null) {
listener = new Listener(consumer);
consumer.setAvailableListener(listener);
}
}
long timeout = getReadTimeout(request);
if (LOG.isDebugEnabled()) {
LOG.debug("Receiving message(s) from: " + destination + " with timeout: " + timeout);
}
Continuation continuation = null;
Listener listener = null;
// Look for any available messages (need a little timeout)
message = consumer.receive(10);
// Get an existing Continuation or create a new one if there are
// no events.
if (message == null) {
continuation = ContinuationSupport.getContinuation(request);
if (continuation.isExpired()) {
response.setStatus(HttpServletResponse.SC_NO_CONTENT);
return;
}
continuation.setTimeout(timeout);
continuation.suspend();
// Fetch the listeners
listener = (Listener)consumer.getAvailableListener();
if (listener == null) {
listener = new Listener(consumer);
consumer.setAvailableListener(listener);
}
// register this continuation with our listener.
listener.setContinuation(continuation);
// Look for any available messages (need a little timeout). Always
// try at least one lookup; don't block past the deadline.
if (timeout <= 0) {
message = consumer.receiveNoWait();
} else if (timeout < 10) {
message = consumer.receive(timeout);
} else {
message = consumer.receive(10);
}
writeResponse(request, response, message);
if (message == null) {
handleContinuation(request, response, client, destination, consumer, deadline);
} else {
writeResponse(request, response, message);
closeConsumerOnOneShot(request, client, destination);
synchronized (activeConsumers) {
activeConsumers.remove(consumer);
}
}
} catch (JMSException e) {
throw new ServletException("Could not post JMS message: " + e, e);
}
}
protected void handleContinuation(HttpServletRequest request, HttpServletResponse response, WebClient client, Destination destination,
MessageAvailableConsumer consumer, long deadline) {
// Get an existing Continuation or create a new one if there are no events.
Continuation continuation = ContinuationSupport.getContinuation(request);
long timeout = deadline - System.currentTimeMillis();
if ((continuation.isExpired()) || (timeout <= 0)) {
// Reset the continuation on the available listener for the consumer to prevent the
// next message receipt from being consumed without a valid, active continuation.
synchronized (consumer) {
Object obj = consumer.getAvailableListener();
if (obj instanceof Listener) {
((Listener) obj).setContinuation(null);
}
}
response.setStatus(HttpServletResponse.SC_NO_CONTENT);
closeConsumerOnOneShot(request, client, destination);
synchronized (activeConsumers) {
activeConsumers.remove(consumer);
}
return;
}
continuation.setTimeout(timeout);
continuation.suspend();
synchronized (consumer) {
Listener listener = (Listener) consumer.getAvailableListener();
// register this continuation with our listener.
listener.setContinuation(continuation);
}
}
protected void writeResponse(HttpServletRequest request, HttpServletResponse response, Message message) throws IOException, JMSException {
int messages = 0;
try {
response.setHeader("Cache-Control", "no-cache, no-store, must-revalidate"); // HTTP 1.1
response.setHeader("Pragma", "no-cache"); // HTTP 1.0
response.setDateHeader("Expires", 0);
response.setHeader("Cache-Control", "no-cache, no-store, must-revalidate"); // HTTP
// 1.1
response.setHeader("Pragma", "no-cache"); // HTTP 1.0
response.setDateHeader("Expires", 0);
// write a responds
PrintWriter writer = response.getWriter();
@ -269,7 +326,7 @@ public class MessageServlet extends MessageServletSupport {
protected void writeMessageResponse(PrintWriter writer, Message message) throws JMSException, IOException {
if (message instanceof TextMessage) {
TextMessage textMsg = (TextMessage)message;
TextMessage textMsg = (TextMessage) message;
String txt = textMsg.getText();
if (txt != null) {
if (txt.startsWith("<?")) {
@ -278,7 +335,7 @@ public class MessageServlet extends MessageServletSupport {
writer.print(txt);
}
} else if (message instanceof ObjectMessage) {
ObjectMessage objectMsg = (ObjectMessage)message;
ObjectMessage objectMsg = (ObjectMessage) message;
Object object = objectMsg.getObject();
if (object != null) {
writer.print(object.toString());
@ -288,7 +345,7 @@ public class MessageServlet extends MessageServletSupport {
protected boolean isXmlContent(Message message) throws JMSException {
if (message instanceof TextMessage) {
TextMessage textMsg = (TextMessage)message;
TextMessage textMsg = (TextMessage) message;
String txt = textMsg.getText();
if (txt != null) {
// assume its xml when it starts with <
@ -304,7 +361,7 @@ public class MessageServlet extends MessageServletSupport {
public WebClient getWebClient(HttpServletRequest request) {
String clientId = request.getParameter("clientId");
if (clientId != null) {
synchronized(this) {
synchronized (this) {
LOG.debug("Getting local client [" + clientId + "]");
WebClient client = clients.get(clientId);
if (client == null) {
@ -338,9 +395,9 @@ public class MessageServlet extends MessageServletSupport {
response.setHeader("id", message.getJMSMessageID());
// Return JMS properties as header values.
for(Enumeration names = message.getPropertyNames(); names.hasMoreElements();) {
for (Enumeration names = message.getPropertyNames(); names.hasMoreElements();) {
String name = (String) names.nextElement();
response.setHeader(name , message.getObjectProperty(name).toString());
response.setHeader(name, message.getObjectProperty(name).toString());
}
}
@ -348,17 +405,37 @@ public class MessageServlet extends MessageServletSupport {
* @return the timeout value for read requests which is always >= 0 and <=
* maximumReadTimeout to avoid DoS attacks
*/
protected long getReadTimeout(HttpServletRequest request) {
long answer = defaultReadTimeout;
protected long getReadDeadline(HttpServletRequest request) {
Long answer;
String name = request.getParameter(readTimeoutParameter);
if (name != null) {
answer = asLong(name);
answer = (Long) request.getAttribute(readTimeoutRequestAtt);
if (answer == null) {
long timeout = defaultReadTimeout;
String name = request.getParameter(readTimeoutParameter);
if (name != null) {
timeout = asLong(name);
}
if (timeout < 0 || timeout > maximumReadTimeout) {
timeout = maximumReadTimeout;
}
answer = Long.valueOf(System.currentTimeMillis() + timeout);
}
if (answer < 0 || answer > maximumReadTimeout) {
answer = maximumReadTimeout;
return answer.longValue();
}
/**
* Close the consumer if one-shot mode is used on the given request.
*/
protected void closeConsumerOnOneShot(HttpServletRequest request, WebClient client, Destination dest) {
if (asBoolean(request.getParameter(oneShotParameter), false)) {
try {
client.closeConsumer(dest);
} catch (JMSException jms_exc) {
LOG.warn("JMS exception on closing consumer after request with one-shot mode", jms_exc);
}
}
return answer;
}
/*
@ -386,17 +463,9 @@ public class MessageServlet extends MessageServletSupport {
synchronized (this.consumer) {
if (continuation != null) {
try {
Message message = consumer.receiveNoWait();
continuation.setAttribute("message", message);
} catch (Exception e) {
LOG.warn("Error receiving message due " + e.getMessage() + ". This exception is ignored.", e);
} finally {
continuation.resume();
}
continuation.resume();
}
}
}
}
}