/*
* 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.coyote.http11.upgrade;
import java.io.IOException;
import javax.servlet.ServletOutputStream;
import org.apache.coyote.http11.upgrade.servlet31.WriteListener;
import org.apache.tomcat.util.ExceptionUtils;
import org.apache.tomcat.util.res.StringManager;
/**
* Implements the new Servlet 3.1 methods for {@link ServletOutputStream}.
*/
public abstract class AbstractServletOutputStream extends ServletOutputStream {
protected static final StringManager sm =
StringManager.getManager(Constants.Package);
// Used to ensure that isReady() and onWritePossible() have a consistent
// view of buffer and fireListener when determining if the listener should
// fire.
private final Object fireListenerLock = new Object();
// Used to ensure that only one thread writes to the socket at a time and
// that buffer is consistently updated with any unwritten data after the
// write. Note it is not necessary to hold this lock when checking if buffer
// contains data but, depending on how the result is used, some form of
// synchronization may be required (see fireListenerLock for an example).
private final Object writeLock = new Object();
private volatile boolean closeRequired = false;
// Start in blocking-mode
private volatile WriteListener listener = null;
// Guarded by fireListenerLock
private volatile boolean fireListener = false;
private volatile ClassLoader applicationLoader = null;
// Writes guarded by writeLock
private volatile byte[] buffer;
private volatile int bufferPos;
private volatile int bufferLimit;
private final int asyncWriteBufferSize;
public AbstractServletOutputStream(int asyncWriteBufferSize) {
this.asyncWriteBufferSize = asyncWriteBufferSize;
buffer = new byte[asyncWriteBufferSize];
}
/**
* New Servlet 3.1 method.
*/
public final boolean isReady() {
if (listener == null) {
throw new IllegalStateException(
sm.getString("upgrade.sos.canWrite.ise"));
}
// Make sure isReady() and onWritePossible() have a consistent view of
// buffer and fireListener when determining if the listener should fire
synchronized (fireListenerLock) {
boolean result = (bufferLimit == 0);
fireListener = !result;
return result;
}
}
/**
* New Servlet 3.1 method.
*/
public final void setWriteListener(WriteListener listener) {
if (listener == null) {
throw new IllegalArgumentException(
sm.getString("upgrade.sos.writeListener.null"));
}
if (this.listener != null) {
throw new IllegalArgumentException(
sm.getString("upgrade.sos.writeListener.set"));
}
this.listener = listener;
this.applicationLoader = Thread.currentThread().getContextClassLoader();
}
protected final boolean isCloseRequired() {
return closeRequired;
}
@Override
public void write(int b) throws IOException {
synchronized (writeLock) {
preWriteChecks();
writeInternal(new byte[] { (byte) b }, 0, 1);
}
}
@Override
public void write(byte[] b, int off, int len) throws IOException {
synchronized (writeLock) {
preWriteChecks();
writeInternal(b, off, len);
}
}
@Override
public void close() throws IOException {
closeRequired = true;
doClose();
}
private void preWriteChecks() {
if (bufferLimit != 0) {
throw new IllegalStateException(sm.getString("upgrade.sis.write.ise"));
}
}
/**
* Must hold writeLock to call this method.
*/
private void writeInternal(byte[] b, int off, int len) throws IOException {
if (listener == null) {
// Simple case - blocking IO
doWrite(true, b, off, len);
} else {
// Non-blocking IO
// If the non-blocking read does not complete, doWrite() will add
// the socket back into the poller. The poller may trigger a new
// write event before this method has finished updating buffer. The
// writeLock sync makes sure that buffer is updated before the next
// write executes.
int written = doWrite(false, b, off, len);
if (written < len) {
if (b == buffer) {
// This is a partial write of the existing buffer. Just
// increment the current position
bufferPos += written;
} else {
// This is a new partial write
int bytesLeft = len - written;
if (bytesLeft > buffer.length) {
buffer = new byte[bytesLeft];
} else if (bytesLeft < asyncWriteBufferSize &&
buffer.length > asyncWriteBufferSize) {
buffer = new byte[asyncWriteBufferSize];
}
bufferPos = 0;
bufferLimit = bytesLeft;
System.arraycopy(b, off + written, buffer, bufferPos, bufferLimit);
}
} else {
bufferLimit = 0;
}
}
}
protected final void onWritePossible() throws IOException {
try {
synchronized (writeLock) {
if (bufferLimit > 0) {
writeInternal(buffer, bufferPos, bufferLimit - bufferPos);
}
}
} catch (Throwable t) {
ExceptionUtils.handleThrowable(t);
onError(t);
if (t instanceof IOException) {
throw (IOException) t;
} else {
throw new IOException(t);
}
}
// Make sure isReady() and onWritePossible() have a consistent view of
// buffer and fireListener when determining if the listener should fire
boolean fire = false;
synchronized (fireListenerLock) {
if (bufferLimit == 0 && fireListener) {
fireListener = false;
fire = true;
}
}
if (fire) {
Thread thread = Thread.currentThread();
ClassLoader originalClassLoader = thread.getContextClassLoader();
try {
thread.setContextClassLoader(applicationLoader);
listener.onWritePossible();
} finally {
thread.setContextClassLoader(originalClassLoader);
}
}
}
protected final void onError(Throwable t) {
if (listener == null) {
return;
}
Thread thread = Thread.currentThread();
ClassLoader originalClassLoader = thread.getContextClassLoader();
try {
thread.setContextClassLoader(applicationLoader);
listener.onError(t);
} finally {
thread.setContextClassLoader(originalClassLoader);
}
}
/**
* Abstract method to be overridden by concrete implementations. The base
* class will ensure that there are no concurrent calls to this method for
* the same socket by ensuring that the writeLock is held when making any
* calls to this method.
*/
protected abstract int doWrite(boolean block, byte[] b, int off, int len)
throws IOException;
protected abstract void doFlush() throws IOException;
protected abstract void doClose() throws IOException;
}