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An HTTP Proxy (aka gateway) in the form of a Java servlet. An
HTTP proxy is useful for AJAX applications to communicate with web
accessible services on hosts other than where the web application is hosted.
The newest version!
/*
* Copyright MITRE
*
* 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.mitre.dsmiley.httpproxy;
import org.apache.http.Header;
import org.apache.http.HttpEntity;
import org.apache.http.HttpEntityEnclosingRequest;
import org.apache.http.HttpHeaders;
import org.apache.http.HttpHost;
import org.apache.http.HttpRequest;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.config.CookieSpecs;
import org.apache.http.client.config.RequestConfig;
import org.apache.http.client.methods.AbortableHttpRequest;
import org.apache.http.client.utils.URIUtils;
import org.apache.http.config.SocketConfig;
import org.apache.http.entity.InputStreamEntity;
import org.apache.http.impl.client.HttpClientBuilder;
import org.apache.http.message.BasicHeader;
import org.apache.http.message.BasicHttpEntityEnclosingRequest;
import org.apache.http.message.BasicHttpRequest;
import org.apache.http.message.HeaderGroup;
import org.apache.http.util.EntityUtils;
import jakarta.servlet.ServletException;
import jakarta.servlet.http.Cookie;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import java.io.Closeable;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.HttpCookie;
import java.net.URI;
import java.util.BitSet;
import java.util.Enumeration;
import java.util.Formatter;
/**
* An HTTP reverse proxy/gateway servlet. It is designed to be extended for customization
* if desired. Most of the work is handled by
* Apache HttpClient.
*
* There are alternatives to a servlet based proxy such as Apache mod_proxy if that is available to you. However
* this servlet is easily customizable by Java, secure-able by your web application's security (e.g. spring-security),
* portable across servlet engines, and is embeddable into another web application.
*
*
* Inspiration: http://httpd.apache.org/docs/2.0/mod/mod_proxy.html
*
*
* @author David Smiley [email protected]
*/
@SuppressWarnings({"deprecation", "serial", "WeakerAccess"})
public class ProxyServlet extends HttpServlet {
/* INIT PARAMETER NAME CONSTANTS */
/** A boolean parameter name to enable logging of input and target URLs to the servlet log. */
public static final String P_LOG = "log";
/** A boolean parameter name to enable forwarding of the client IP */
public static final String P_FORWARDEDFOR = "forwardip";
/** A boolean parameter name to keep HOST parameter as-is */
public static final String P_PRESERVEHOST = "preserveHost";
/** A boolean parameter name to keep COOKIES as-is */
public static final String P_PRESERVECOOKIES = "preserveCookies";
/** A boolean parameter name to keep COOKIE path as-is */
public static final String P_PRESERVECOOKIEPATH = "preserveCookiePath";
/** A boolean parameter name to have auto-handle redirects */
public static final String P_HANDLEREDIRECTS = "http.protocol.handle-redirects"; // ClientPNames.HANDLE_REDIRECTS
/** An integer parameter name to set the socket connection timeout (millis) */
public static final String P_CONNECTTIMEOUT = "http.socket.timeout"; // CoreConnectionPNames.SO_TIMEOUT
/** An integer parameter name to set the socket read timeout (millis) */
public static final String P_READTIMEOUT = "http.read.timeout";
/** An integer parameter name to set the connection request timeout (millis) */
public static final String P_CONNECTIONREQUESTTIMEOUT = "http.connectionrequest.timeout";
/** An integer parameter name to set max connection number */
public static final String P_MAXCONNECTIONS = "http.maxConnections";
/** A boolean parameter whether to use JVM-defined system properties to configure various networking aspects. */
public static final String P_USESYSTEMPROPERTIES = "useSystemProperties";
/** A boolean parameter to enable handling of compression in the servlet. If it is false, compressed streams are passed through unmodified. */
public static final String P_HANDLECOMPRESSION = "handleCompression";
/** The parameter name for the target (destination) URI to proxy to. */
public static final String P_TARGET_URI = "targetUri";
protected static final String ATTR_TARGET_URI =
ProxyServlet.class.getSimpleName() + ".targetUri";
protected static final String ATTR_TARGET_HOST =
ProxyServlet.class.getSimpleName() + ".targetHost";
/* MISC */
protected boolean doLog = false;
protected boolean doForwardIP = true;
/** User agents shouldn't send the url fragment but what if it does? */
protected boolean doSendUrlFragment = true;
protected boolean doPreserveHost = false;
protected boolean doPreserveCookies = false;
protected boolean doPreserveCookiePath = false;
protected boolean doHandleRedirects = false;
protected boolean useSystemProperties = true;
protected boolean doHandleCompression = false;
protected int connectTimeout = -1;
protected int readTimeout = -1;
protected int connectionRequestTimeout = -1;
protected int maxConnections = -1;
//These next 3 are cached here, and should only be referred to in initialization logic. See the
// ATTR_* parameters.
/** From the configured parameter "targetUri". */
protected String targetUri;
protected URI targetUriObj;//new URI(targetUri)
protected HttpHost targetHost;//URIUtils.extractHost(targetUriObj);
private HttpClient proxyClient;
@Override
public String getServletInfo() {
return "A proxy servlet by David Smiley, [email protected]";
}
protected String getTargetUri(HttpServletRequest servletRequest) {
return (String) servletRequest.getAttribute(ATTR_TARGET_URI);
}
protected HttpHost getTargetHost(HttpServletRequest servletRequest) {
return (HttpHost) servletRequest.getAttribute(ATTR_TARGET_HOST);
}
/**
* Reads a configuration parameter. By default it reads servlet init parameters but
* it can be overridden.
*/
protected String getConfigParam(String key) {
return getServletConfig().getInitParameter(key);
}
@Override
public void init() throws ServletException {
String doLogStr = getConfigParam(P_LOG);
if (doLogStr != null) {
this.doLog = Boolean.parseBoolean(doLogStr);
}
String doForwardIPString = getConfigParam(P_FORWARDEDFOR);
if (doForwardIPString != null) {
this.doForwardIP = Boolean.parseBoolean(doForwardIPString);
}
String preserveHostString = getConfigParam(P_PRESERVEHOST);
if (preserveHostString != null) {
this.doPreserveHost = Boolean.parseBoolean(preserveHostString);
}
String preserveCookiesString = getConfigParam(P_PRESERVECOOKIES);
if (preserveCookiesString != null) {
this.doPreserveCookies = Boolean.parseBoolean(preserveCookiesString);
}
String preserveCookiePathString = getConfigParam(P_PRESERVECOOKIEPATH);
if (preserveCookiePathString != null) {
this.doPreserveCookiePath = Boolean.parseBoolean(preserveCookiePathString);
}
String handleRedirectsString = getConfigParam(P_HANDLEREDIRECTS);
if (handleRedirectsString != null) {
this.doHandleRedirects = Boolean.parseBoolean(handleRedirectsString);
}
String connectTimeoutString = getConfigParam(P_CONNECTTIMEOUT);
if (connectTimeoutString != null) {
this.connectTimeout = Integer.parseInt(connectTimeoutString);
}
String readTimeoutString = getConfigParam(P_READTIMEOUT);
if (readTimeoutString != null) {
this.readTimeout = Integer.parseInt(readTimeoutString);
}
String connectionRequestTimeout = getConfigParam(P_CONNECTIONREQUESTTIMEOUT);
if (connectionRequestTimeout != null) {
this.connectionRequestTimeout = Integer.parseInt(connectionRequestTimeout);
}
String maxConnections = getConfigParam(P_MAXCONNECTIONS);
if (maxConnections != null) {
this.maxConnections = Integer.parseInt(maxConnections);
}
String useSystemPropertiesString = getConfigParam(P_USESYSTEMPROPERTIES);
if (useSystemPropertiesString != null) {
this.useSystemProperties = Boolean.parseBoolean(useSystemPropertiesString);
}
String doHandleCompression = getConfigParam(P_HANDLECOMPRESSION);
if (doHandleCompression != null) {
this.doHandleCompression = Boolean.parseBoolean(doHandleCompression);
}
initTarget();//sets target*
proxyClient = createHttpClient();
}
/**
* Sub-classes can override specific behaviour of {@link org.apache.http.client.config.RequestConfig}.
*/
protected RequestConfig buildRequestConfig() {
return RequestConfig.custom()
.setRedirectsEnabled(doHandleRedirects)
.setCookieSpec(CookieSpecs.IGNORE_COOKIES) // we handle them in the servlet instead
.setConnectTimeout(connectTimeout)
.setSocketTimeout(readTimeout)
.setConnectionRequestTimeout(connectionRequestTimeout)
.build();
}
/**
* Sub-classes can override specific behaviour of {@link org.apache.http.config.SocketConfig}.
*/
protected SocketConfig buildSocketConfig() {
if (readTimeout < 1) {
return null;
}
return SocketConfig.custom()
.setSoTimeout(readTimeout)
.build();
}
protected void initTarget() throws ServletException {
targetUri = getConfigParam(P_TARGET_URI);
if (targetUri == null)
throw new ServletException(P_TARGET_URI+" is required.");
//test it's valid
try {
targetUriObj = new URI(targetUri);
} catch (Exception e) {
throw new ServletException("Trying to process targetUri init parameter: "+e,e);
}
targetHost = URIUtils.extractHost(targetUriObj);
}
/**
* Called from {@link #init(jakarta.servlet.ServletConfig)}.
* HttpClient offers many opportunities for customization.
* In any case, it should be thread-safe.
*/
protected HttpClient createHttpClient() {
HttpClientBuilder clientBuilder = getHttpClientBuilder()
.setDefaultRequestConfig(buildRequestConfig())
.setDefaultSocketConfig(buildSocketConfig());
clientBuilder.setMaxConnTotal(maxConnections);
clientBuilder.setMaxConnPerRoute(maxConnections);
if(! doHandleCompression) {
clientBuilder.disableContentCompression();
}
if (useSystemProperties)
clientBuilder = clientBuilder.useSystemProperties();
return buildHttpClient(clientBuilder);
}
/**
* Creates a HttpClient from the given builder. Meant as postprocessor
* to possibly adapt the client builder prior to creating the
* HttpClient.
*
* @param clientBuilder pre-configured client builder
* @return HttpClient
*/
protected HttpClient buildHttpClient(HttpClientBuilder clientBuilder) {
return clientBuilder.build();
}
/**
* Creates a {@code HttpClientBuilder}. Meant as preprocessor to possibly
* adapt the client builder prior to any configuration got applied.
*
* @return HttpClient builder
*/
protected HttpClientBuilder getHttpClientBuilder() {
return HttpClientBuilder.create();
}
/**
* The http client used.
* @see #createHttpClient()
*/
protected HttpClient getProxyClient() {
return proxyClient;
}
@Override
public void destroy() {
//Usually, clients implement Closeable:
if (proxyClient instanceof Closeable) {
try {
((Closeable) proxyClient).close();
} catch (IOException e) {
log("While destroying servlet, shutting down HttpClient: "+e, e);
}
} else {
//Older releases require we do this:
if (proxyClient != null)
proxyClient.getConnectionManager().shutdown();
}
super.destroy();
}
@Override
protected void service(HttpServletRequest servletRequest, HttpServletResponse servletResponse)
throws ServletException, IOException {
//initialize request attributes from caches if unset by a subclass by this point
if (servletRequest.getAttribute(ATTR_TARGET_URI) == null) {
servletRequest.setAttribute(ATTR_TARGET_URI, targetUri);
}
if (servletRequest.getAttribute(ATTR_TARGET_HOST) == null) {
servletRequest.setAttribute(ATTR_TARGET_HOST, targetHost);
}
// Make the Request
//note: we won't transfer the protocol version because I'm not sure it would truly be compatible
String method = servletRequest.getMethod();
String proxyRequestUri = rewriteUrlFromRequest(servletRequest);
HttpRequest proxyRequest;
//spec: RFC 2616, sec 4.3: either of these two headers signal that there is a message body.
if (servletRequest.getHeader(HttpHeaders.CONTENT_LENGTH) != null ||
servletRequest.getHeader(HttpHeaders.TRANSFER_ENCODING) != null) {
proxyRequest = newProxyRequestWithEntity(method, proxyRequestUri, servletRequest);
} else {
proxyRequest = new BasicHttpRequest(method, proxyRequestUri);
}
copyRequestHeaders(servletRequest, proxyRequest);
setXForwardedForHeader(servletRequest, proxyRequest);
HttpResponse proxyResponse = null;
try {
// Execute the request
proxyResponse = doExecute(servletRequest, servletResponse, proxyRequest);
// Process the response:
int statusCode = proxyResponse.getStatusLine().getStatusCode();
servletResponse.setStatus(statusCode);
// Copying response headers to make sure SESSIONID or other Cookie which comes from the remote
// server will be saved in client when the proxied url was redirected to another one.
// See issue [#51](https://github.com/mitre/HTTP-Proxy-Servlet/issues/51)
copyResponseHeaders(proxyResponse, servletRequest, servletResponse);
if (statusCode == HttpServletResponse.SC_NOT_MODIFIED) {
// 304 needs special handling. See:
// http://www.ics.uci.edu/pub/ietf/http/rfc1945.html#Code304
// Don't send body entity/content!
servletResponse.setIntHeader(HttpHeaders.CONTENT_LENGTH, 0);
} else {
// Send the content to the client
copyResponseEntity(proxyResponse, servletResponse, proxyRequest, servletRequest);
}
} catch (Exception e) {
handleRequestException(proxyRequest, proxyResponse, e);
} finally {
// make sure the entire entity was consumed, so the connection is released
if (proxyResponse != null)
EntityUtils.consumeQuietly(proxyResponse.getEntity());
//Note: Don't need to close servlet outputStream:
// http://stackoverflow.com/questions/1159168/should-one-call-close-on-httpservletresponse-getoutputstream-getwriter
}
}
protected void handleRequestException(HttpRequest proxyRequest, HttpResponse proxyResonse, Exception e) throws ServletException, IOException {
//abort request, according to best practice with HttpClient
if (proxyRequest instanceof AbortableHttpRequest) {
AbortableHttpRequest abortableHttpRequest = (AbortableHttpRequest) proxyRequest;
abortableHttpRequest.abort();
}
// If the response is a chunked response, it is read to completion when
// #close is called. If the sending site does not timeout or keeps sending,
// the connection will be kept open indefinitely. Closing the respone
// object terminates the stream.
if (proxyResonse instanceof Closeable) {
((Closeable) proxyResonse).close();
}
if (e instanceof RuntimeException)
throw (RuntimeException)e;
if (e instanceof ServletException)
throw (ServletException)e;
//noinspection ConstantConditions
if (e instanceof IOException)
throw (IOException) e;
throw new RuntimeException(e);
}
protected HttpResponse doExecute(HttpServletRequest servletRequest, HttpServletResponse servletResponse,
HttpRequest proxyRequest) throws IOException {
if (doLog) {
log("proxy " + servletRequest.getMethod() + " uri: " + servletRequest.getRequestURI() + " -- " +
proxyRequest.getRequestLine().getUri());
}
return proxyClient.execute(getTargetHost(servletRequest), proxyRequest);
}
protected HttpRequest newProxyRequestWithEntity(String method, String proxyRequestUri,
HttpServletRequest servletRequest)
throws IOException {
HttpEntityEnclosingRequest eProxyRequest =
new BasicHttpEntityEnclosingRequest(method, proxyRequestUri);
// Add the input entity (streamed)
// note: we don't bother ensuring we close the servletInputStream since the container handles it
eProxyRequest.setEntity(
new InputStreamEntity(servletRequest.getInputStream(), getContentLength(servletRequest)));
return eProxyRequest;
}
// Get the header value as a long in order to more correctly proxy very large requests
private long getContentLength(HttpServletRequest request) {
String contentLengthHeader = request.getHeader("Content-Length");
if (contentLengthHeader != null) {
return Long.parseLong(contentLengthHeader);
}
return -1L;
}
protected void closeQuietly(Closeable closeable) {
try {
closeable.close();
} catch (IOException e) {
log(e.getMessage(), e);
}
}
/** These are the "hop-by-hop" headers that should not be copied.
* http://www.w3.org/Protocols/rfc2616/rfc2616-sec13.html
* I use an HttpClient HeaderGroup class instead of Set<String> because this
* approach does case insensitive lookup faster.
*/
protected static final HeaderGroup hopByHopHeaders;
static {
hopByHopHeaders = new HeaderGroup();
String[] headers = new String[] {
"Connection", "Keep-Alive", "Proxy-Authenticate", "Proxy-Authorization",
"TE", "Trailers", "Transfer-Encoding", "Upgrade" };
for (String header : headers) {
hopByHopHeaders.addHeader(new BasicHeader(header, null));
}
}
/**
* Copy request headers from the servlet client to the proxy request.
* This is easily overridden to add your own.
*/
protected void copyRequestHeaders(HttpServletRequest servletRequest, HttpRequest proxyRequest) {
// Get an Enumeration of all of the header names sent by the client
@SuppressWarnings("unchecked")
Enumeration enumerationOfHeaderNames = servletRequest.getHeaderNames();
while (enumerationOfHeaderNames.hasMoreElements()) {
String headerName = enumerationOfHeaderNames.nextElement();
copyRequestHeader(servletRequest, proxyRequest, headerName);
}
}
/**
* Copy a request header from the servlet client to the proxy request.
* This is easily overridden to filter out certain headers if desired.
*/
protected void copyRequestHeader(HttpServletRequest servletRequest, HttpRequest proxyRequest,
String headerName) {
//Instead the content-length is effectively set via InputStreamEntity
if (headerName.equalsIgnoreCase(HttpHeaders.CONTENT_LENGTH))
return;
if (hopByHopHeaders.containsHeader(headerName))
return;
// If compression is handled in the servlet, apache http client needs to
// control the Accept-Encoding header, not the client
if (doHandleCompression && headerName.equalsIgnoreCase(HttpHeaders.ACCEPT_ENCODING))
return;
@SuppressWarnings("unchecked")
Enumeration headers = servletRequest.getHeaders(headerName);
while (headers.hasMoreElements()) {//sometimes more than one value
String headerValue = headers.nextElement();
// In case the proxy host is running multiple virtual servers,
// rewrite the Host header to ensure that we get content from
// the correct virtual server
if (!doPreserveHost && headerName.equalsIgnoreCase(HttpHeaders.HOST)) {
HttpHost host = getTargetHost(servletRequest);
headerValue = host.getHostName();
if (host.getPort() != -1)
headerValue += ":"+host.getPort();
} else if (!doPreserveCookies && headerName.equalsIgnoreCase(org.apache.http.cookie.SM.COOKIE)) {
headerValue = getRealCookie(headerValue);
}
proxyRequest.addHeader(headerName, headerValue);
}
}
private void setXForwardedForHeader(HttpServletRequest servletRequest,
HttpRequest proxyRequest) {
if (doForwardIP) {
String forHeaderName = "X-Forwarded-For";
String forHeader = servletRequest.getRemoteAddr();
String existingForHeader = servletRequest.getHeader(forHeaderName);
if (existingForHeader != null) {
forHeader = existingForHeader + ", " + forHeader;
}
proxyRequest.setHeader(forHeaderName, forHeader);
String protoHeaderName = "X-Forwarded-Proto";
String protoHeader = servletRequest.getScheme();
proxyRequest.setHeader(protoHeaderName, protoHeader);
}
}
/** Copy proxied response headers back to the servlet client. */
protected void copyResponseHeaders(HttpResponse proxyResponse, HttpServletRequest servletRequest,
HttpServletResponse servletResponse) {
for (Header header : proxyResponse.getAllHeaders()) {
copyResponseHeader(servletRequest, servletResponse, header);
}
}
/** Copy a proxied response header back to the servlet client.
* This is easily overwritten to filter out certain headers if desired.
*/
protected void copyResponseHeader(HttpServletRequest servletRequest,
HttpServletResponse servletResponse, Header header) {
String headerName = header.getName();
if (hopByHopHeaders.containsHeader(headerName))
return;
String headerValue = header.getValue();
if (headerName.equalsIgnoreCase(org.apache.http.cookie.SM.SET_COOKIE) ||
headerName.equalsIgnoreCase(org.apache.http.cookie.SM.SET_COOKIE2)) {
copyProxyCookie(servletRequest, servletResponse, headerValue);
} else if (headerName.equalsIgnoreCase(HttpHeaders.LOCATION)) {
// LOCATION Header may have to be rewritten.
servletResponse.addHeader(headerName, rewriteUrlFromResponse(servletRequest, headerValue));
} else {
servletResponse.addHeader(headerName, headerValue);
}
}
/**
* Copy cookie from the proxy to the servlet client.
* Replaces cookie path to local path and renames cookie to avoid collisions.
*/
protected void copyProxyCookie(HttpServletRequest servletRequest,
HttpServletResponse servletResponse, String headerValue) {
for (HttpCookie cookie : HttpCookie.parse(headerValue)) {
Cookie servletCookie = createProxyCookie(servletRequest, cookie);
servletResponse.addCookie(servletCookie);
}
}
/**
* Creates a proxy cookie from the original cookie.
*
* @param servletRequest original request
* @param cookie original cookie
* @return proxy cookie
*/
protected Cookie createProxyCookie(HttpServletRequest servletRequest, HttpCookie cookie) {
String proxyCookieName = getProxyCookieName(cookie);
Cookie servletCookie = new Cookie(proxyCookieName, cookie.getValue());
servletCookie.setPath(this.doPreserveCookiePath ?
cookie.getPath() : // preserve original cookie path
buildProxyCookiePath(servletRequest) //set to the path of the proxy servlet
);
servletCookie.setComment(cookie.getComment());
servletCookie.setMaxAge((int) cookie.getMaxAge());
// don't set cookie domain
servletCookie.setSecure(servletRequest.isSecure() && cookie.getSecure());
servletCookie.setVersion(cookie.getVersion());
servletCookie.setHttpOnly(cookie.isHttpOnly());
return servletCookie;
}
/**
* Set cookie name prefixed with a proxy value so it won't collide with other cookies.
*
* @param cookie cookie to get proxy cookie name for
* @return non-conflicting proxy cookie name
*/
protected String getProxyCookieName(HttpCookie cookie) {
//
return doPreserveCookies ? cookie.getName() : getCookieNamePrefix(cookie.getName()) + cookie.getName();
}
/**
* Create path for proxy cookie.
*
* @param servletRequest original request
* @return proxy cookie path
*/
protected String buildProxyCookiePath(HttpServletRequest servletRequest) {
String path = servletRequest.getContextPath(); // path starts with / or is empty string
path += servletRequest.getServletPath(); // servlet path starts with / or is empty string
if (path.isEmpty()) {
path = "/";
}
return path;
}
/**
* Take any client cookies that were originally from the proxy and prepare them to send to the
* proxy. This relies on cookie headers being set correctly according to RFC 6265 Sec 5.4.
* This also blocks any local cookies from being sent to the proxy.
*/
protected String getRealCookie(String cookieValue) {
StringBuilder escapedCookie = new StringBuilder();
String cookies[] = cookieValue.split("[;,]");
for (String cookie : cookies) {
String cookieSplit[] = cookie.split("=");
if (cookieSplit.length == 2) {
String cookieName = cookieSplit[0].trim();
if (cookieName.startsWith(getCookieNamePrefix(cookieName))) {
cookieName = cookieName.substring(getCookieNamePrefix(cookieName).length());
if (escapedCookie.length() > 0) {
escapedCookie.append("; ");
}
escapedCookie.append(cookieName).append("=").append(cookieSplit[1].trim());
}
}
}
return escapedCookie.toString();
}
/** The string prefixing rewritten cookies. */
protected String getCookieNamePrefix(String name) {
return "!Proxy!" + getServletConfig().getServletName();
}
/** Copy response body data (the entity) from the proxy to the servlet client. */
protected void copyResponseEntity(HttpResponse proxyResponse, HttpServletResponse servletResponse,
HttpRequest proxyRequest, HttpServletRequest servletRequest)
throws IOException {
HttpEntity entity = proxyResponse.getEntity();
if (entity != null) {
if (entity.isChunked()) {
// Flush intermediate results before blocking on input -- needed for SSE
InputStream is = entity.getContent();
OutputStream os = servletResponse.getOutputStream();
byte[] buffer = new byte[10 * 1024];
int read;
while ((read = is.read(buffer)) != -1) {
os.write(buffer, 0, read);
/*-
* Issue in Apache http client/JDK: if the stream from client is
* compressed, apache http client will delegate to GzipInputStream.
* The #available implementation of InflaterInputStream (parent of
* GzipInputStream) return 1 until EOF is reached. This is not
* consistent with InputStream#available, which defines:
*
* A single read or skip of this many bytes will not block,
* but may read or skip fewer bytes.
*
* To work around this, a flush is issued always if compression
* is handled by apache http client
*/
if (doHandleCompression || is.available() == 0 /* next is.read will block */) {
os.flush();
}
}
// Entity closing/cleanup is done in the caller (#service)
} else {
OutputStream servletOutputStream = servletResponse.getOutputStream();
entity.writeTo(servletOutputStream);
}
}
}
/**
* Reads the request URI from {@code servletRequest} and rewrites it, considering targetUri.
* It's used to make the new request.
*/
protected String rewriteUrlFromRequest(HttpServletRequest servletRequest) {
StringBuilder uri = new StringBuilder(500);
uri.append(getTargetUri(servletRequest));
// Handle the path given to the servlet
String pathInfo = rewritePathInfoFromRequest(servletRequest);
if (pathInfo != null) {//ex: /my/path.html
// getPathInfo() returns decoded string, so we need encodeUriQuery to encode "%" characters
uri.append(encodeUriQuery(pathInfo, true));
}
// Handle the query string & fragment
String queryString = servletRequest.getQueryString();//ex:(following '?'): name=value&foo=bar#fragment
String fragment = null;
//split off fragment from queryString, updating queryString if found
if (queryString != null) {
int fragIdx = queryString.indexOf('#');
if (fragIdx >= 0) {
fragment = queryString.substring(fragIdx + 1);
queryString = queryString.substring(0,fragIdx);
}
}
queryString = rewriteQueryStringFromRequest(servletRequest, queryString);
if (queryString != null && queryString.length() > 0) {
uri.append('?');
// queryString is not decoded, so we need encodeUriQuery not to encode "%" characters, to avoid double-encoding
uri.append(encodeUriQuery(queryString, false));
}
if (doSendUrlFragment && fragment != null) {
uri.append('#');
// fragment is not decoded, so we need encodeUriQuery not to encode "%" characters, to avoid double-encoding
uri.append(encodeUriQuery(fragment, false));
}
return uri.toString();
}
protected String rewriteQueryStringFromRequest(HttpServletRequest servletRequest, String queryString) {
return queryString;
}
/**
* Allow overrides of {@link jakarta.servlet.http.HttpServletRequest#getPathInfo()}.
* Useful when url-pattern of servlet-mapping (web.xml) requires manipulation.
*/
protected String rewritePathInfoFromRequest(HttpServletRequest servletRequest) {
return servletRequest.getPathInfo();
}
/**
* For a redirect response from the target server, this translates {@code theUrl} to redirect to
* and translates it to one the original client can use.
*/
protected String rewriteUrlFromResponse(HttpServletRequest servletRequest, String theUrl) {
//TODO document example paths
final String targetUri = getTargetUri(servletRequest);
if (theUrl.startsWith(targetUri)) {
/*-
* The URL points back to the back-end server.
* Instead of returning it verbatim we replace the target path with our
* source path in a way that should instruct the original client to
* request the URL pointed through this Proxy.
* We do this by taking the current request and rewriting the path part
* using this servlet's absolute path and the path from the returned URL
* after the base target URL.
*/
StringBuffer curUrl = servletRequest.getRequestURL();//no query
int pos;
// Skip the protocol part
if ((pos = curUrl.indexOf("://"))>=0) {
// Skip the authority part
// + 3 to skip the separator between protocol and authority
if ((pos = curUrl.indexOf("/", pos + 3)) >=0) {
// Trim everything after the authority part.
curUrl.setLength(pos);
}
}
// Context path starts with a / if it is not blank
curUrl.append(servletRequest.getContextPath());
// Servlet path starts with a / if it is not blank
curUrl.append(servletRequest.getServletPath());
curUrl.append(theUrl, targetUri.length(), theUrl.length());
return curUrl.toString();
}
return theUrl;
}
/** The target URI as configured. Not null. */
public String getTargetUri() { return targetUri; }
/**
* Encodes characters in the query or fragment part of the URI.
*
* Unfortunately, an incoming URI sometimes has characters disallowed by the spec. HttpClient
* insists that the outgoing proxied request has a valid URI because it uses Java's {@link URI}.
* To be more forgiving, we must escape the problematic characters. See the URI class for the
* spec.
*
* @param in example: name=value&foo=bar#fragment
* @param encodePercent determine whether percent characters need to be encoded
*/
protected CharSequence encodeUriQuery(CharSequence in, boolean encodePercent) {
//Note that I can't simply use URI.java to encode because it will escape pre-existing escaped things.
StringBuilder outBuf = null;
Formatter formatter = null;
for(int i = 0; i < in.length(); i++) {
char c = in.charAt(i);
boolean escape = true;
if (c < 128) {
if (asciiQueryChars.get(c) && !(encodePercent && c == '%')) {
escape = false;
}
} else if (!Character.isISOControl(c) && !Character.isSpaceChar(c)) {//not-ascii
escape = false;
}
if (!escape) {
if (outBuf != null)
outBuf.append(c);
} else {
//escape
if (outBuf == null) {
outBuf = new StringBuilder(in.length() + 5*3);
outBuf.append(in,0,i);
formatter = new Formatter(outBuf);
}
//leading %, 0 padded, width 2, capital hex
formatter.format("%%%02X",(int)c);//TODO
}
}
return outBuf != null ? outBuf : in;
}
protected static final BitSet asciiQueryChars;
static {
char[] c_unreserved = "_-!.~'()*".toCharArray();//plus alphanum
char[] c_punct = ",;:$&+=".toCharArray();
char[] c_reserved = "/@".toCharArray();//plus punct. Exclude '?'; RFC-2616 3.2.2. Exclude '[', ']'; https://www.ietf.org/rfc/rfc1738.txt, unsafe characters
asciiQueryChars = new BitSet(128);
for(char c = 'a'; c <= 'z'; c++) asciiQueryChars.set(c);
for(char c = 'A'; c <= 'Z'; c++) asciiQueryChars.set(c);
for(char c = '0'; c <= '9'; c++) asciiQueryChars.set(c);
for(char c : c_unreserved) asciiQueryChars.set(c);
for(char c : c_punct) asciiQueryChars.set(c);
for(char c : c_reserved) asciiQueryChars.set(c);
asciiQueryChars.set('%');//leave existing percent escapes in place
}
}
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