/*
* Copyright (c) 2002-2012 Alibaba Group Holding Limited.
* All rights reserved.
*
* 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 com.alibaba.citrus.service.requestcontext.buffered.impl;
import static com.alibaba.citrus.util.BasicConstant.*;
import static com.alibaba.citrus.util.CollectionUtil.*;
import static com.alibaba.citrus.util.ObjectUtil.*;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.io.Writer;
import java.util.EmptyStackException;
import java.util.LinkedList;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletResponse;
import com.alibaba.citrus.service.requestcontext.RequestContext;
import com.alibaba.citrus.service.requestcontext.support.AbstractResponseWrapper;
import com.alibaba.citrus.util.internal.Servlet3Util.Servlet3OutputStream;
import com.alibaba.citrus.util.io.ByteArray;
import com.alibaba.citrus.util.io.ByteArrayInputStream;
import com.alibaba.citrus.util.io.ByteArrayOutputStream;
import com.alibaba.citrus.util.io.StreamUtil;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* 包裹<code>HttpServletResponse</code>，使之输出到内存中。
*
* @author Michael Zhou
*/
public class BufferedResponseImpl extends AbstractResponseWrapper {
private static final Logger log = LoggerFactory.getLogger(BufferedResponseImpl.class);
private boolean buffering = true;
private Stack<ByteArrayOutputStream> bytesStack;
private Stack<StringWriter> charsStack;
private ServletOutputStream stream;
private PrintWriter streamAdapter;
private PrintWriter writer;
private ServletOutputStream writerAdapter;
/**
* 创建一个<code>BufferedResponseImpl</code>。
*
* @param requestContext response所在的request context
* @param response 原始的response
*/
public BufferedResponseImpl(RequestContext requestContext, HttpServletResponse response) {
super(requestContext, response);
}
/**
* 取得输出流。
*
* @return response的输出流
* @throws IOException 输入输出失败
*/
@Override
public ServletOutputStream getOutputStream() throws IOException {
if (stream != null) {
return stream;
}
if (writer != null) {
// 如果getWriter方法已经被调用，则将writer转换成OutputStream
// 这样做会增加少量额外的内存开销，但标准的servlet engine不会遇到这种情形，
// 只有少数servlet engine需要这种做法（resin）。
if (writerAdapter != null) {
return writerAdapter;
} else {
log.debug("Attampt to getOutputStream after calling getWriter. This may cause unnecessary system cost.");
writerAdapter = new WriterOutputStream(writer, getCharacterEncoding());
return writerAdapter;
}
}
if (buffering) {
// 注意，servletStream一旦创建，就不改变，
// 如果需要改变，只需要改变其下面的bytes流即可。
if (bytesStack == null) {
bytesStack = new Stack<ByteArrayOutputStream>();
}
ByteArrayOutputStream bytes = new ByteArrayOutputStream();
bytesStack.push(bytes);
stream = new BufferedServletOutputStream(bytes);
log.debug("Created new byte buffer");
} else {
stream = super.getOutputStream();
}
return stream;
}
/**
* 取得输出字符流。
*
* @return response的输出字符流
* @throws IOException 输入输出失败
*/
@Override
public PrintWriter getWriter() throws IOException {
if (writer != null) {
return writer;
}
if (stream != null) {
// 如果getOutputStream方法已经被调用，则将stream转换成PrintWriter。
// 这样做会增加少量额外的内存开销，但标准的servlet engine不会遇到这种情形，
// 只有少数servlet engine需要这种做法（resin）。
if (streamAdapter != null) {
return streamAdapter;
} else {
log.debug("Attampt to getWriter after calling getOutputStream. This may cause unnecessary system cost.");
streamAdapter = new PrintWriter(new OutputStreamWriter(stream, getCharacterEncoding()), true);
return streamAdapter;
}
}
if (buffering) {
// 注意，servletWriter一旦创建，就不改变，
// 如果需要改变，只需要改变其下面的chars流即可。
if (charsStack == null) {
charsStack = new Stack<StringWriter>();
}
StringWriter chars = new StringWriter();
charsStack.push(chars);
writer = new BufferedServletWriter(chars);
log.debug("Created new character buffer");
} else {
writer = super.getWriter();
}
return writer;
}
/**
* 设置content长度。该调用只在<code>setBuffering(false)</code>时有效。
*
* @param length content长度
*/
@Override
public void setContentLength(int length) {
if (!buffering) {
super.setContentLength(length);
}
}
/**
* 冲洗buffer。
*
* @throws IOException 如果失败
*/
@Override
public void flushBuffer() throws IOException {
if (buffering) {
flushBufferAdapter();
if (writer != null) {
writer.flush();
} else if (stream != null) {
stream.flush();
}
} else {
super.flushBuffer();
}
}
/**
* 清除所有buffers，常用于显示出错信息。
*
* @throws IllegalStateException 如果response已经commit
*/
@Override
public void resetBuffer() {
if (buffering) {
flushBufferAdapter();
if (stream != null) {
bytesStack.clear();
bytesStack.add(new ByteArrayOutputStream());
((BufferedServletOutputStream) stream).updateOutputStream(bytesStack.peek());
}
if (writer != null) {
charsStack.clear();
charsStack.add(new StringWriter());
((BufferedServletWriter) writer).updateWriter(charsStack.peek());
}
}
super.resetBuffer();
}
/**
* 设置是否将所有信息保存在内存中。
*
* @return 如果是，则返回<code>true</code>
*/
public boolean isBuffering() {
return buffering;
}
/**
* 设置buffer模式，如果设置成<code>true</code>，表示将所有信息保存在内存中，否则直接输出到原始response中。
* <p>
* 此方法必须在<code>getOutputStream</code>和<code>getWriter</code>方法之前执行，否则将抛出
* <code>IllegalStateException</code>。
* </p>
*
* @param buffering 是否buffer内容
* @throws IllegalStateException <code>getOutputStream</code>或
* <code>getWriter</code>方法已经被执行
*/
public void setBuffering(boolean buffering) {
if (stream == null && writer == null) {
if (this.buffering != buffering) {
this.buffering = buffering;
log.debug("Set buffering " + (buffering ? "on" : "off"));
}
} else {
if (this.buffering != buffering) {
throw new IllegalStateException(
"Unable to change the buffering mode since the getOutputStream() or getWriter() method has been called");
}
}
}
/**
* 创建新的buffer，保存老的buffer。
*
* @throws IllegalStateException 如果不在buffer模式，或<code>getWriter</code>
* 方法曾被调用，或<code>getOutputStream</code>方法从未被调用
*/
public void pushBuffer() {
if (!buffering) {
throw new IllegalStateException("Buffering mode is required to pushBuffer");
}
if (stream == null && writer == null) {
throw new IllegalStateException("getOutputStream() or getWriter() method has not been called yet");
}
flushBufferAdapter();
// 向stream或writer stack中压入新的buffer。
if (stream != null) {
ByteArrayOutputStream bytes = new ByteArrayOutputStream();
bytesStack.push(bytes);
((BufferedServletOutputStream) stream).updateOutputStream(bytesStack.peek());
log.debug("Pushed new byte buffer (stack size is " + bytesStack.size() + ")");
} else {
StringWriter chars = new StringWriter();
charsStack.push(chars);
((BufferedServletWriter) writer).updateWriter(charsStack.peek());
log.debug("Pushed new character buffer (stack size is " + charsStack.size() + ")");
}
}
/**
* 弹出最近的buffer，如果堆栈中只有一个buffer，则弹出后再创建一个新的。
*
* @return 最近的buffer内容，如果<code>getOutputStream</code>方法从未被调用，则返回空的byte array
* @throws IllegalStateException 如果不在buffer模式，或<code>getWriter</code>方法曾被调用
*/
public ByteArray popByteBuffer() {
if (!buffering) {
throw new IllegalStateException("Buffering mode is required to popByteBuffer");
}
if (writer != null) {
throw new IllegalStateException("Unable to popByteBuffer() since the getWriter() method has been called");
}
if (stream == null) {
return new ByteArray(EMPTY_BYTE_ARRAY, 0, 0);
} else {
flushBufferAdapter();
ByteArrayOutputStream block = bytesStack.pop();
if (bytesStack.size() == 0) {
bytesStack.push(new ByteArrayOutputStream());
}
((BufferedServletOutputStream) stream).updateOutputStream(bytesStack.peek());
log.debug("Popped the last byte buffer (stack size is " + bytesStack.size() + ")");
return block.toByteArray();
}
}
/**
* 弹出最近的buffer，如果堆栈中只有一个buffer，则弹出后再创建一个新的。
*
* @return 最近的buffer内容，如果<code>getWriter</code>方法从未被调用，则返回空的字符串
* @throws IllegalStateException 如果不在buffer模式，或<code>getOutputStream</code>
* 方法曾被调用
*/
public String popCharBuffer() {
if (!buffering) {
throw new IllegalStateException("Buffering mode is required to popCharBuffer");
}
if (stream != null) {
throw new IllegalStateException(
"Unable to popCharBuffer() since the getOutputStream() method has been called");
}
if (writer == null) {
return EMPTY_STRING;
} else {
flushBufferAdapter();
StringWriter block = charsStack.pop();
if (charsStack.size() == 0) {
charsStack.push(new StringWriter());
}
((BufferedServletWriter) writer).updateWriter(charsStack.peek());
log.debug("Popped the last character buffer (stack size is " + charsStack.size() + ")");
return block.toString();
}
}
/**
* 将buffer中的内容提交到真正的servlet输出流中。
* <p>
* 如果从来没有执行过<code>getOutputStream</code>或<code>getWriter</code>
* 方法，则该方法不做任何事情。
* </p>
*
* @throws IOException 如果输入输出失败
* @throws IllegalStateException 如果不是在buffer模式，或buffer栈中不止一个buffer
*/
public void commitBuffer() throws IOException {
if (stream == null && writer == null) {
return;
}
if (!buffering) {
throw new IllegalStateException("Buffering mode is required for commitBuffer");
}
// 输出bytes
if (stream != null) {
if (bytesStack.size() > 1) {
throw new IllegalStateException("More than 1 byte-buffers in the stack");
}
flushBufferAdapter();
OutputStream ostream = super.getOutputStream();
ByteArray bytes = popByteBuffer();
bytes.writeTo(ostream);
log.debug("Committed buffered bytes to the Servlet output stream");
}
// 输出chars
if (writer != null) {
if (charsStack.size() > 1) {
throw new IllegalStateException("More than 1 char-buffers in the stack");
}
flushBufferAdapter();
PrintWriter writer = super.getWriter();
String chars = popCharBuffer();
writer.write(chars);
log.debug("Committed buffered characters to the Servlet writer");
}
}
/** 冲洗buffer adapter，确保adapter中的信息被写入buffer中。 */
private void flushBufferAdapter() {
if (streamAdapter != null) {
streamAdapter.flush();
}
if (writerAdapter != null) {
try {
writerAdapter.flush();
} catch (IOException e) {
}
}
}
/**
* 从<code>LinkedList</code>继承的stack，避免<code>java.util.Stack</code>
* 中synchronized的代价。
*/
private static class Stack<T> {
private final LinkedList<T> list = createLinkedList();
public T peek() {
if (list.isEmpty()) {
throw new EmptyStackException();
}
return list.getLast();
}
public void push(T object) {
list.addLast(object);
}
public T pop() {
if (list.isEmpty()) {
throw new EmptyStackException();
}
return list.removeLast();
}
public int size() {
return list.size();
}
public boolean add(T o) {
return list.add(o);
}
public void clear() {
list.clear();
}
}
/** 代表一个将内容保存在内存中的<code>ServletOutputStream</code>。 */
private static class BufferedServletOutputStream extends Servlet3OutputStream {
private ByteArrayOutputStream bytes;
public BufferedServletOutputStream(ByteArrayOutputStream bytes) {
super(null);
this.bytes = bytes;
}
public void updateOutputStream(ByteArrayOutputStream bytes) {
this.bytes = bytes;
}
@Override
public void write(int b) throws IOException {
bytes.write((byte) b);
}
@Override
public void write(byte[] b) throws IOException {
write(b, 0, b.length);
}
@Override
public void write(byte[] b, int off, int len) throws IOException {
bytes.write(b, off, len);
}
@Override
public void flush() throws IOException {
bytes.flush();
}
@Override
public void close() throws IOException {
bytes.flush();
bytes.close();
}
}
/** 代表一个将内容保存在内存中的<code>PrintWriter</code>。 */
private static class BufferedServletWriter extends PrintWriter {
public BufferedServletWriter(StringWriter chars) {
super(chars);
}
public void updateWriter(StringWriter chars) {
this.out = chars;
}
}
/** 将<code>Writer</code>适配到<code>ServletOutputStream</code>。 */
private static class WriterOutputStream extends Servlet3OutputStream {
private ByteArrayOutputStream buffer = new ByteArrayOutputStream();
private Writer writer;
private String charset;
public WriterOutputStream(Writer writer, String charset) {
super(null);
this.writer = writer;
this.charset = defaultIfNull(charset, "ISO-8859-1");
}
@Override
public void write(int b) throws IOException {
buffer.write((byte) b);
}
@Override
public void write(byte[] b) throws IOException {
buffer.write(b, 0, b.length);
}
@Override
public void write(byte[] b, int off, int len) throws IOException {
buffer.write(b, off, len);
}
@Override
public void flush() throws IOException {
ByteArray bytes = buffer.toByteArray();
if (bytes.getLength() > 0) {
ByteArrayInputStream inputBytes = new ByteArrayInputStream(bytes.getRawBytes(), bytes.getOffset(),
bytes.getLength());
InputStreamReader reader = new InputStreamReader(inputBytes, charset);
StreamUtil.io(reader, writer, true, false);
writer.flush();
buffer.reset();
}
}
@Override
public void close() throws IOException {
this.flush();
}
}
}