org.apache.james.protocols.api.AbstractProtocolTransport Maven / Gradle / Ivy
/****************************************************************
* Licensed to the Apache Software Foundation (ASF) under one *
* or more contributor license agreements. See the NOTICE file *
* distributed with this work for additional information *
* regarding copyright ownership. The ASF licenses this file *
* to you 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.apache.james.protocols.api;
import java.io.InputStream;
import java.io.UnsupportedEncodingException;
import java.util.List;
import java.util.Queue;
import java.util.concurrent.LinkedBlockingQueue;
import org.apache.james.protocols.api.future.FutureResponse;
import org.apache.james.protocols.api.future.FutureResponse.ResponseListener;
/**
* Abstract base class for {@link ProtocolTransport} implementation which already takes care of all the complex
* stuff when handling {@link Response}'s.
*
*
*
*/
public abstract class AbstractProtocolTransport implements ProtocolTransport{
private final static String CRLF = "\r\n";
// TODO: Should we limit the size ?
private final Queue responses = new LinkedBlockingQueue();
private volatile boolean isAsync = false;
/**
* @see org.apache.james.protocols.api.ProtocolTransport#writeResponse(org.apache.james.protocols.api.Response, org.apache.james.protocols.api.ProtocolSession)
*/
public final void writeResponse(Response response, ProtocolSession session) {
// if we already in asynchrnous mode we simply enqueue the response
// we do this synchronously because we may have a dequeuer thread working on
// isAsync and responses.
boolean enqueued = false;
synchronized(this) {
if (isAsync == true) {
responses.offer(response);
enqueued = true;
}
}
// if we didn't enqueue then we check if the response is writable or we have to
// set us "asynchrnous" and wait for response to be ready.
if (!enqueued) {
if (isResponseWritable(response)) {
writeResponseToClient(response, session);
} else {
addDequeuerListener(response, session);
isAsync = true;
}
}
}
/**
* Helper method which tries to write all queued {@link Response}'s to the remote client. This method is aware of {@link FutureResponse} and makes sure the {@link Response}'s are written
* in the correct order
*
* This is related to PROTOCOLS-36
*
* @param session
*/
private void writeQueuedResponses(ProtocolSession session) {
// dequeue Responses until non is left
while (true) {
Response queuedResponse = null;
// synchrnously we check responses and if it is empty we move back to non asynch
// behaviour
synchronized(this) {
queuedResponse = responses.poll();
if (queuedResponse == null) {
isAsync = false;
break;
}
}
// if we have something in the queue we continue writing until we
// find something asynchronous.
if (isResponseWritable(queuedResponse)) {
writeResponseToClient(queuedResponse, session);
} else {
addDequeuerListener(queuedResponse, session);
// no changes to isAsync here, because in this method we are always already async.
break;
}
}
}
private boolean isResponseWritable(Response response) {
return !(response instanceof FutureResponse) || ((FutureResponse) response).isReady();
}
private void addDequeuerListener(Response response, final ProtocolSession session) {
((FutureResponse) response).addListener(new ResponseListener() {
public void onResponse(FutureResponse response) {
writeResponseToClient(response, session);
writeQueuedResponses(session);
}
});
}
/**
* Write the {@link Response} to the client
*
* @param response
* @param session
*/
protected void writeResponseToClient(Response response, ProtocolSession session) {
if (response != null) {
boolean startTLS = false;
if (response instanceof StartTlsResponse) {
if (isStartTLSSupported()) {
startTLS = true;
} else {
// StartTls is not supported by this transport, so throw a exception
throw new UnsupportedOperationException("StartTls is not supported by this ProtocolTransport implementation");
}
}
if (response instanceof StreamResponse) {
writeToClient(toBytes(response), session, false);
writeToClient(((StreamResponse) response).getStream(), session, startTLS);
} else {
writeToClient(toBytes(response), session, startTLS);
}
// reset state on starttls
if (startTLS) {
session.resetState();
}
if (response.isEndSession()) {
// close the channel if needed after the message was written out
close();
}
}
}
/**
* Take the {@link Response} and encode it to a byte array
*
* @param response
* @return bytes
*/
protected static byte[] toBytes(Response response) {
StringBuilder builder = new StringBuilder();
List lines = response.getLines();
for (int i = 0; i < lines.size(); i++) {
builder.append(lines.get(i));
if (i < lines.size()) {
builder.append(CRLF);
}
}
try {
return builder.toString().getBytes("US-ASCII");
} catch (UnsupportedEncodingException e) {
throw new RuntimeException("No US-ASCII ?");
}
}
/**
* Write the given byte's to the remote peer
*
* @param bytes the bytes to write
* @param session the {@link ProtocolSession} for the write request
* @param startTLS true if startTLS should be started after the bytes were written to the client
*/
protected abstract void writeToClient(byte[] bytes, ProtocolSession session, boolean startTLS);
/**
* Write the given {@link InputStream} to the remote peer
*
* @param in the {@link InputStream} which should be written back to the client
* @param session the {@link ProtocolSession} for the write request
* @param startTLS true if startTLS should be started after the {@link InputStream} was written to the client
*/
protected abstract void writeToClient(InputStream in, ProtocolSession session, boolean startTLS);
/**
* Close the Transport
*/
protected abstract void close();
}
© 2015 - 2025 Weber Informatics LLC | Privacy Policy