Java tutorial
/* * Copyright 2002-2017 the original author or authors. * * 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 * * https://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.springframework.web.util; import java.io.IOException; import java.io.InputStream; import java.io.OutputStreamWriter; import java.io.PrintWriter; import java.io.UnsupportedEncodingException; import javax.servlet.ServletOutputStream; import javax.servlet.WriteListener; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpServletResponseWrapper; import org.springframework.lang.Nullable; import org.springframework.util.FastByteArrayOutputStream; /** * {@link javax.servlet.http.HttpServletResponse} wrapper that caches all content written to * the {@linkplain #getOutputStream() output stream} and {@linkplain #getWriter() writer}, * and allows this content to be retrieved via a {@link #getContentAsByteArray() byte array}. * * <p>Used e.g. by {@link org.springframework.web.filter.ShallowEtagHeaderFilter}. * Note: As of Spring Framework 5.0, this wrapper is built on the Servlet 3.1 API. * * @author Juergen Hoeller * @since 4.1.3 * @see ContentCachingRequestWrapper */ public class ContentCachingResponseWrapper extends HttpServletResponseWrapper { private final FastByteArrayOutputStream content = new FastByteArrayOutputStream(1024); @Nullable private ServletOutputStream outputStream; @Nullable private PrintWriter writer; private int statusCode = HttpServletResponse.SC_OK; @Nullable private Integer contentLength; /** * Create a new ContentCachingResponseWrapper for the given servlet response. * @param response the original servlet response */ public ContentCachingResponseWrapper(HttpServletResponse response) { super(response); } @Override public void setStatus(int sc) { super.setStatus(sc); this.statusCode = sc; } @SuppressWarnings("deprecation") @Override public void setStatus(int sc, String sm) { super.setStatus(sc, sm); this.statusCode = sc; } @Override public void sendError(int sc) throws IOException { copyBodyToResponse(false); try { super.sendError(sc); } catch (IllegalStateException ex) { // Possibly on Tomcat when called too late: fall back to silent setStatus super.setStatus(sc); } this.statusCode = sc; } @Override @SuppressWarnings("deprecation") public void sendError(int sc, String msg) throws IOException { copyBodyToResponse(false); try { super.sendError(sc, msg); } catch (IllegalStateException ex) { // Possibly on Tomcat when called too late: fall back to silent setStatus super.setStatus(sc, msg); } this.statusCode = sc; } @Override public void sendRedirect(String location) throws IOException { copyBodyToResponse(false); super.sendRedirect(location); } @Override public ServletOutputStream getOutputStream() throws IOException { if (this.outputStream == null) { this.outputStream = new ResponseServletOutputStream(getResponse().getOutputStream()); } return this.outputStream; } @Override public PrintWriter getWriter() throws IOException { if (this.writer == null) { String characterEncoding = getCharacterEncoding(); this.writer = (characterEncoding != null ? new ResponsePrintWriter(characterEncoding) : new ResponsePrintWriter(WebUtils.DEFAULT_CHARACTER_ENCODING)); } return this.writer; } @Override public void flushBuffer() throws IOException { // do not flush the underlying response as the content as not been copied to it yet } @Override public void setContentLength(int len) { if (len > this.content.size()) { this.content.resize(len); } this.contentLength = len; } // Overrides Servlet 3.1 setContentLengthLong(long) at runtime public void setContentLengthLong(long len) { if (len > Integer.MAX_VALUE) { throw new IllegalArgumentException("Content-Length exceeds ContentCachingResponseWrapper's maximum (" + Integer.MAX_VALUE + "): " + len); } int lenInt = (int) len; if (lenInt > this.content.size()) { this.content.resize(lenInt); } this.contentLength = lenInt; } @Override public void setBufferSize(int size) { if (size > this.content.size()) { this.content.resize(size); } } @Override public void resetBuffer() { this.content.reset(); } @Override public void reset() { super.reset(); this.content.reset(); } /** * Return the status code as specified on the response. */ public int getStatusCode() { return this.statusCode; } /** * Return the cached response content as a byte array. */ public byte[] getContentAsByteArray() { return this.content.toByteArray(); } /** * Return an {@link InputStream} to the cached content. * @since 4.2 */ public InputStream getContentInputStream() { return this.content.getInputStream(); } /** * Return the current size of the cached content. * @since 4.2 */ public int getContentSize() { return this.content.size(); } /** * Copy the complete cached body content to the response. * @since 4.2 */ public void copyBodyToResponse() throws IOException { copyBodyToResponse(true); } /** * Copy the cached body content to the response. * @param complete whether to set a corresponding content length * for the complete cached body content * @since 4.2 */ protected void copyBodyToResponse(boolean complete) throws IOException { if (this.content.size() > 0) { HttpServletResponse rawResponse = (HttpServletResponse) getResponse(); if ((complete || this.contentLength != null) && !rawResponse.isCommitted()) { rawResponse.setContentLength(complete ? this.content.size() : this.contentLength); this.contentLength = null; } this.content.writeTo(rawResponse.getOutputStream()); this.content.reset(); if (complete) { super.flushBuffer(); } } } private class ResponseServletOutputStream extends ServletOutputStream { private final ServletOutputStream os; public ResponseServletOutputStream(ServletOutputStream os) { this.os = os; } @Override public void write(int b) throws IOException { content.write(b); } @Override public void write(byte[] b, int off, int len) throws IOException { content.write(b, off, len); } @Override public boolean isReady() { return this.os.isReady(); } @Override public void setWriteListener(WriteListener writeListener) { this.os.setWriteListener(writeListener); } } private class ResponsePrintWriter extends PrintWriter { public ResponsePrintWriter(String characterEncoding) throws UnsupportedEncodingException { super(new OutputStreamWriter(content, characterEncoding)); } @Override public void write(char[] buf, int off, int len) { super.write(buf, off, len); super.flush(); } @Override public void write(String s, int off, int len) { super.write(s, off, len); super.flush(); } @Override public void write(int c) { super.write(c); super.flush(); } } }