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Created June 29, 2012 17:54
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Errai Servlet
/*
* Copyright 2011 JBoss, by Red Hat, Inc
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.jboss.errai.bus.server.servlet;
import org.jboss.errai.bus.client.api.Message;
import org.jboss.errai.bus.client.api.QueueSession;
import org.jboss.errai.bus.client.api.base.MessageBuilder;
import org.jboss.errai.bus.client.framework.ClientMessageBus;
import org.jboss.errai.bus.server.api.MessageQueue;
import org.jboss.errai.bus.server.service.ErraiServiceConfigurator;
import org.jboss.errai.marshalling.client.Marshalling;
import org.jboss.errai.marshalling.client.api.ParserFactory;
import org.jboss.errai.marshalling.client.api.json.EJArray;
import org.jboss.errai.marshalling.client.api.json.EJValue;
import org.jboss.errai.marshalling.client.marshallers.ErraiProtocolEnvelopeMarshaller;
import org.jboss.errai.marshalling.server.DecodingSession;
import org.jboss.errai.marshalling.server.MappingContextSingleton;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import static org.jboss.errai.bus.server.io.MessageFactory.createCommandMessage;
/**
* The default DefaultBlockingServlet which provides the HTTP-protocol gateway
* between the server bus and the client buses.
* <p/>
* <h2>Configuration</h2>
* <p/>
* The DefaultBlockingServlet, as its name suggests, is normally configured as
* an HTTP Servlet in the <code>web.xml</code> file:
* <p/>
* <pre>
* {@code <servlet>}
* {@code <servlet-name>ErraiServlet</servlet-name>}
* {@code <servlet-class>org.jboss.errai.bus.server.servlet.DefaultBlockingServlet</servlet-class>}
* {@code <load-on-startup>1</load-on-startup>}
* {@code </servlet>}
*
* {@code <servlet-mapping>}
* {@code <servlet-name>ErraiServlet</servlet-name>}
* {@code <url-pattern>*.erraiBus</url-pattern>}
* {@code </servlet-mapping>}
* </pre>
* <p/>
* Alternatively, the DefaultBlockingServlet can be deployed as a Servlet
* Filter. This may be necessary in cases where an existing filter is configured
* in the web application, and that filter interferes with the Errai Bus
* requests. In this case, configuring DefaultBlockingServlet to handle
* {@code *.erraiBus} requests ahead of other filters in web.xml will solve the
* problem:
* <p/>
* <pre>
* {@code <filter>}
* {@code <filter-name>ErraiServlet</filter-name>}
* {@code <filter-class>org.jboss.errai.bus.server.servlet.DefaultBlockingServlet</filter-class>}
* {@code </filter>}
*
* {@code <filter-mapping>}
* {@code <filter-name>ErraiServlet</filter-name>}
* {@code <url-pattern>*.erraiBus</url-pattern>}
* {@code </filter-mapping>}
*
* {@code <!-- other filter-mapping and servlet-mapping elements go here -->}
* </pre>
*/
public class DefaultBlockingServlet extends AbstractErraiServlet implements Filter {
/**
* Called by the server (via the <tt>service</tt> method) to allow a servlet to handle a GET request by supplying
* a response
*
* @param httpServletRequest
* - object that contains the request the client has made of the servlet
* @param httpServletResponse
* - object that contains the response the servlet sends to the client
*
* @throws IOException
* - if an input or output error is detected when the servlet handles the GET request
* @throws ServletException
* - if the request for the GET could not be handled
*/
@Override
protected void doGet(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse)
throws ServletException, IOException {
pollForMessages(sessionProvider.createOrGetSession(httpServletRequest.getSession(),
httpServletRequest.getHeader(ClientMessageBus.REMOTE_QUEUE_ID_HEADER)),
httpServletRequest, httpServletResponse, ErraiServiceConfigurator.LONG_POLLING);
}
/**
* Called by the server (via the <code>service</code> method) to allow a servlet to handle a POST request, by
* sending the request
*
* @param httpServletRequest
* - object that contains the request the client has made of the servlet
* @param httpServletResponse
* - object that contains the response the servlet sends to the client
*
* @throws IOException
* - if an input or output error is detected when the servlet handles the request
* @throws ServletException
* - if the request for the POST could not be handled
*/
@Override
protected void doPost(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse)
throws ServletException, IOException {
final QueueSession session = sessionProvider.createOrGetSession(httpServletRequest.getSession(),
httpServletRequest.getHeader(ClientMessageBus.REMOTE_QUEUE_ID_HEADER));
final List<Message> commandMessage = createCommandMessage(session, httpServletRequest);
final Message message = MessageBuilder.createMessage()
.toSubject("Penis")
.signalling()
.with("Foo", new ArrayList<String>(Arrays.asList(new String[]{"foo", "bar"})))
.with("Bar", true)
.noErrorHandling().getMessage();
String json = Marshalling.toJSON(message.getParts());
service.store(commandMessage);
pollForMessages(session, httpServletRequest, httpServletResponse, false);
}
private void pollForMessages(QueueSession session, HttpServletRequest httpServletRequest,
HttpServletResponse httpServletResponse, boolean wait) throws IOException {
try {
// note about caching: clients now include a uniquifier in a request parameter called "z"
// so no-cache headers are now unnecessary.
httpServletResponse.setContentType("application/json");
final MessageQueue queue = service.getBus().getQueue(session);
final ServletOutputStream outputStream = httpServletResponse.getOutputStream();
if (queue == null) {
switch (getConnectionPhase(httpServletRequest)) {
case CONNECTING:
case DISCONNECTING:
return;
}
sendDisconnectDueToSessionExpiry(outputStream);
return;
}
queue.heartBeat();
final StringBuilder sb = new StringBuilder();
OutputStream outputStream1 = new OutputStream() {
@Override
public void write(int b) throws IOException {
sb.append((char) b);
outputStream.write(b);
}
};
queue.poll(wait, outputStream1);
System.out.println("Transmitting to client: " + sb.toString());
EJValue val = ParserFactory.get().parse(sb.toString());
final EJArray ejArray = val.isArray();
if (ejArray != null) {
for (int i = 0; i < ejArray.size(); i++) {
Object o =
ErraiProtocolEnvelopeMarshaller.INSTANCE.demarshall(ejArray.get(i),
new DecodingSession(MappingContextSingleton.get()));
System.out.println(o);
}
}
outputStream.close();
}
catch (final Throwable t) {
t.printStackTrace();
writeExceptionToOutputStream(httpServletResponse, t);
}
}
@Override
public void init(FilterConfig filterConfig) throws ServletException {
super.initAsFilter(filterConfig);
}
/**
* Services this request in the same way as it would be serviced if configured
* as a Servlet. Does not invoke any filters further down the chain. See the
* class-level comment for the reason why this servlet might be configured as a
* filter.
*/
@Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
throws IOException, ServletException {
service(request, response);
}
}
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