Java tutorial
package com.google.gwt.jolokia.server.servlet; /** * 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. */ import java.io.Closeable; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.lang.reflect.Constructor; import java.net.HttpCookie; import java.net.URI; import java.util.BitSet; import java.util.Enumeration; import java.util.Formatter; import java.util.List; import java.util.Properties; import javax.naming.InitialContext; import javax.naming.NamingException; import javax.servlet.ServletException; import javax.servlet.http.Cookie; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; 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.methods.AbortableHttpRequest; import org.apache.http.client.params.ClientPNames; import org.apache.http.client.params.CookiePolicy; import org.apache.http.client.utils.URIUtils; import org.apache.http.entity.InputStreamEntity; import org.apache.http.impl.client.DefaultHttpClient; import org.apache.http.impl.conn.tsccm.ThreadSafeClientConnManager; 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.params.BasicHttpParams; import org.apache.http.params.HttpParams; import org.apache.http.util.EntityUtils; /** * An HTTP reverse proxy/gateway servlet. It is designed to be extended for * customization if desired. Most of the work is handled by <a * href="http://hc.apache.org/httpcomponents-client-ga/">Apache HttpClient</a>. * <p> * 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. * </p> * <p> * Inspiration: http://httpd.apache.org/docs/2.0/mod/mod_proxy.html * </p> * * @author David Smiley dsmiley@mitre.org */ public class ProxyServlet extends HttpServlet { /* INIT PARAMETER NAME CONSTANTS */ private static final long serialVersionUID = 1316958284576030044L; /** * 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"; /** The parameter name for the target (destination) URI to proxy to. */ protected static final String P_TARGET_URI = "targetUri"; protected static final String P_TARGET_JNDI_PROPERTIES = "jndi.properties"; protected static final String P_TARGET_PROPERTIES_TARGET_URI_NAME = "properties.targetURIPropertyName"; 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; // 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, dsmiley@apache.org"; } protected String getTargetUri(HttpServletRequest servletRequest) { return (String) servletRequest.getAttribute(ATTR_TARGET_URI); } private 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); } initTarget();// sets target* HttpParams hcParams = new BasicHttpParams(); hcParams.setParameter(ClientPNames.COOKIE_POLICY, CookiePolicy.IGNORE_COOKIES); readConfigParam(hcParams, ClientPNames.HANDLE_REDIRECTS, Boolean.class); proxyClient = createHttpClient(hcParams); } protected void initTarget() throws ServletException { // First try to get it from environment, maybe maven. targetUri = System.getProperty(P_TARGET_URI); log("unable to find in environment param"); if (targetUri == null) { targetUri = getConfigParam(P_TARGET_URI); } // Try to load target uri from the jndi properties if available. final String jndiPropertiesParam = getConfigParam(P_TARGET_JNDI_PROPERTIES); if (targetUri == null && jndiPropertiesParam != null) { log("Attempting to read jndi properties " + jndiPropertiesParam); Properties props = loadJndiProperties(jndiPropertiesParam); final String jndiTargetParamName = getConfigParam(P_TARGET_PROPERTIES_TARGET_URI_NAME); if (jndiTargetParamName == null) { log("You did not specify a parameter for " + P_TARGET_PROPERTIES_TARGET_URI_NAME + " targetUri will be looked for in the jndi properties"); } if (props != null) { targetUri = props.getProperty(jndiTargetParamName, P_TARGET_URI); } } if (targetUri == null) { Properties props = loadProperties(); if (props != null) { targetUri = props.getProperty("targetUri"); } } if (targetUri == null) throw new ServletException(P_TARGET_URI + " is required."); // test it's valid log("targetUri is " + targetUri); 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(javax.servlet.ServletConfig)}. HttpClient offers * many opportunities for customization. By default, <a href= * "http://hc.apache.org/httpcomponents-client-ga/httpclient/apidocs/org/apache/http/impl/client/SystemDefaultHttpClient.html" * > SystemDefaultHttpClient</a> is used if available, otherwise it falls * back to: * * <pre> * new DefaultHttpClient(new ThreadSafeClientConnManager(), hcParams) * </pre> * * SystemDefaultHttpClient uses PoolingClientConnectionManager. In any case, * it should be thread-safe. */ @SuppressWarnings({ "unchecked", "deprecation" }) protected HttpClient createHttpClient(HttpParams hcParams) { try { // as of HttpComponents v4.2, this class is better since it uses // System // Properties: Class<?> clientClazz = Class.forName("org.apache.http.impl.client.SystemDefaultHttpClient"); Constructor<?> constructor = clientClazz.getConstructor(HttpParams.class); return (HttpClient) constructor.newInstance(hcParams); } catch (ClassNotFoundException e) { // no problem; use v4.1 below } catch (Exception e) { throw new RuntimeException(e); } // Fallback on using older client: return new DefaultHttpClient(new ThreadSafeClientConnManager(), hcParams); } /** * The http client used. * * @see #createHttpClient(HttpParams) */ protected HttpClient getProxyClient() { return proxyClient; } /** * Reads a servlet config parameter by the name {@code hcParamName} of type * {@code type}, and set it in {@code hcParams}. */ protected void readConfigParam(HttpParams hcParams, String hcParamName, Class type) { String val_str = getConfigParam(hcParamName); if (val_str == null) return; Object val_obj; if (type == String.class) { val_obj = val_str; } else { try { // noinspection unchecked val_obj = type.getMethod("valueOf", String.class).invoke(type, val_str); } catch (Exception e) { throw new RuntimeException(e); } } hcParams.setParameter(hcParamName, val_obj); } @Override public void destroy() { // As of HttpComponents v4.3, clients implement closeable if (proxyClient instanceof Closeable) {// TODO AutoCloseable in Java 1.6 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) { 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(), servletRequest.getContentLength())); proxyRequest = eProxyRequest; } else proxyRequest = new BasicHttpRequest(method, proxyRequestUri); copyRequestHeaders(servletRequest, proxyRequest); setXForwardedForHeader(servletRequest, proxyRequest); //debugProxyRequest(proxyRequest); HttpResponse proxyResponse = null; try { // Execute the request if (doLog) { log("proxy " + method + " uri: " + servletRequest.getRequestURI() + " -- " + proxyRequest.getRequestLine().getUri()); } proxyResponse = proxyClient.execute(getTargetHost(servletRequest), proxyRequest); // Process the response int statusCode = proxyResponse.getStatusLine().getStatusCode(); if (doResponseRedirectOrNotModifiedLogic(servletRequest, servletResponse, proxyResponse, statusCode)) { // the response is already "committed" now without any body to // send // TODO copy response headers? return; } // Pass the response code. This method with the "reason phrase" is // deprecated but it's the only way to pass the // reason along too. // noinspection deprecation servletResponse.setStatus(statusCode, proxyResponse.getStatusLine().getReasonPhrase()); copyResponseHeaders(proxyResponse, servletRequest, servletResponse); // Send the content to the client copyResponseEntity(proxyResponse, servletResponse); } catch (Exception e) { // abort request, according to best practice with HttpClient if (proxyRequest instanceof AbortableHttpRequest) { AbortableHttpRequest abortableHttpRequest = (AbortableHttpRequest) proxyRequest; abortableHttpRequest.abort(); } 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); } finally { // make sure the entire entity was consumed, so the connection is // released if (proxyResponse != null) 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 boolean doResponseRedirectOrNotModifiedLogic(HttpServletRequest servletRequest, HttpServletResponse servletResponse, HttpResponse proxyResponse, int statusCode) throws ServletException, IOException { // Check if the proxy response is a redirect // The following code is adapted from // org.tigris.noodle.filters.CheckForRedirect if (statusCode >= HttpServletResponse.SC_MULTIPLE_CHOICES /* 300 */ && statusCode < HttpServletResponse.SC_NOT_MODIFIED /* 304 */) { Header locationHeader = proxyResponse.getLastHeader(HttpHeaders.LOCATION); if (locationHeader == null) { throw new ServletException("Received status code: " + statusCode + " but no " + HttpHeaders.LOCATION + " header was found in the response"); } // Modify the redirect to go to this proxy servlet rather that the // proxied host String locStr = rewriteUrlFromResponse(servletRequest, locationHeader.getValue()); servletResponse.sendRedirect(locStr); return true; } // 304 needs special handling. See: // http://www.ics.uci.edu/pub/ietf/http/rfc1945.html#Code304 // We get a 304 whenever passed an 'If-Modified-Since' // header and the data on disk has not changed; server // responds w/ a 304 saying I'm not going to send the // body because the file has not changed. if (statusCode == HttpServletResponse.SC_NOT_MODIFIED) { servletResponse.setIntHeader(HttpHeaders.CONTENT_LENGTH, 0); servletResponse.setStatus(HttpServletResponse.SC_NOT_MODIFIED); return true; } return false; } protected void closeQuietly(Closeable closeable) { try { closeable.close(); } catch (IOException e) { log(e.getMessage(), e); } } /** * HttpClient v4.1 doesn't have the * {@link org.apache.http.util.EntityUtils#consumeQuietly(org.apache.http.HttpEntity)} * method. */ protected void consumeQuietly(HttpEntity entity) { try { EntityUtils.consume(entity); } catch (IOException e) {// ignore 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. */ protected void copyRequestHeaders(HttpServletRequest servletRequest, HttpRequest proxyRequest) { // Get an Enumeration of all of the header names sent by the client Enumeration enumerationOfHeaderNames = servletRequest.getHeaderNames(); while (enumerationOfHeaderNames.hasMoreElements()) { String headerName = (String) enumerationOfHeaderNames.nextElement(); // Instead the content-length is effectively set via // InputStreamEntity if (headerName.equalsIgnoreCase(HttpHeaders.CONTENT_LENGTH)) continue; if (hopByHopHeaders.containsHeader(headerName)) continue; Enumeration headers = servletRequest.getHeaders(headerName); while (headers.hasMoreElements()) {// sometimes more than one value String headerValue = (String) 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 (headerName.equalsIgnoreCase(HttpHeaders.HOST)) { HttpHost host = getTargetHost(servletRequest); headerValue = host.getHostName(); if (host.getPort() != -1) headerValue += ":" + host.getPort(); } else if (headerName.equalsIgnoreCase(org.apache.http.cookie.SM.COOKIE)) { headerValue = getRealCookie(headerValue); } proxyRequest.addHeader(headerName, headerValue); } } } private void setXForwardedForHeader(HttpServletRequest servletRequest, HttpRequest proxyRequest) { String headerName = "X-Forwarded-For"; if (doForwardIP) { String newHeader = servletRequest.getRemoteAddr(); String existingHeader = servletRequest.getHeader(headerName); if (existingHeader != null) { newHeader = existingHeader + ", " + newHeader; } proxyRequest.setHeader(headerName, newHeader); } } /** Copy proxied response headers back to the servlet client. */ protected void copyResponseHeaders(HttpResponse proxyResponse, HttpServletRequest servletRequest, HttpServletResponse servletResponse) { for (Header header : proxyResponse.getAllHeaders()) { if (hopByHopHeaders.containsHeader(header.getName())) continue; if (header.getName().equals(org.apache.http.cookie.SM.SET_COOKIE) || header.getName().equals(org.apache.http.cookie.SM.SET_COOKIE2)) { copyProxyCookie(servletRequest, servletResponse, header); } else { servletResponse.addHeader(header.getName(), header.getValue()); } } } /** * 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, Header header) { List<HttpCookie> cookies = HttpCookie.parse(header.getValue()); String path = getServletContext().getServletContextName(); if (path == null) { path = ""; } path += servletRequest.getServletPath(); for (HttpCookie cookie : cookies) { // set cookie name prefixed w/ a proxy value so it won't collide w/ // other cookies String proxyCookieName = getCookieNamePrefix() + cookie.getName(); Cookie servletCookie = new Cookie(proxyCookieName, cookie.getValue()); servletCookie.setComment(cookie.getComment()); servletCookie.setMaxAge((int) cookie.getMaxAge()); servletCookie.setPath(path); // set to the path of the proxy servlet // don't set cookie domain servletCookie.setSecure(cookie.getSecure()); servletCookie.setVersion(cookie.getVersion()); servletResponse.addCookie(servletCookie); } } /** * 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]; if (cookieName.startsWith(getCookieNamePrefix())) { cookieName = cookieName.substring(getCookieNamePrefix().length()); if (escapedCookie.length() > 0) { escapedCookie.append("; "); } escapedCookie.append(cookieName).append("=").append(cookieSplit[1]); } } cookieValue = escapedCookie.toString(); } return cookieValue; } /** The string prefixing rewritten cookies. */ protected String getCookieNamePrefix() { return "!Proxy!" + getServletConfig().getServletName(); } /** * Copy response body data (the entity) from the proxy to the servlet * client. */ protected void copyResponseEntity(HttpResponse proxyResponse, HttpServletResponse servletResponse) throws IOException { HttpEntity entity = proxyResponse.getEntity(); if (entity != null) { 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 if (servletRequest.getPathInfo() != null) {// ex: /my/path.html uri.append(encodeUriQuery(servletRequest.getPathInfo())); } // 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('?'); uri.append(encodeUriQuery(queryString)); } if (doSendUrlFragment && fragment != null) { uri.append('#'); uri.append(encodeUriQuery(fragment)); } return uri.toString(); } protected String rewriteQueryStringFromRequest(HttpServletRequest servletRequest, String queryString) { return queryString; } /** * 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)) { String curUrl = servletRequest.getRequestURL().toString();// no // query String pathInfo = servletRequest.getPathInfo(); if (pathInfo != null) { assert curUrl.endsWith(pathInfo); curUrl = curUrl.substring(0, curUrl.length() - pathInfo.length());// take // pathInfo // off } theUrl = curUrl + theUrl.substring(targetUri.length()); } 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. * * <p> * 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 */ protected static CharSequence encodeUriQuery(CharSequence in) { // 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((int) 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 asciiQueryChars = new BitSet(128); for (char c = 'a'; c <= 'z'; c++) asciiQueryChars.set((int) c); for (char c = 'A'; c <= 'Z'; c++) asciiQueryChars.set((int) c); for (char c = '0'; c <= '9'; c++) asciiQueryChars.set((int) c); for (char c : c_unreserved) asciiQueryChars.set((int) c); for (char c : c_punct) asciiQueryChars.set((int) c); for (char c : c_reserved) asciiQueryChars.set((int) c); asciiQueryChars.set((int) '%');// leave existing percent escapes in // place } private Properties loadProperties() { Properties properties = new Properties(); InputStream stream = ProxyServlet.class.getResourceAsStream("/jolokiaproxy.properties"); if (stream != null) { try { properties.load(stream); } catch (IOException e) { // Properties will be empty; } } return properties; } private Properties loadJndiProperties(String jndiResourceName) { Properties props = null; InitialContext ic; try { ic = new InitialContext(); Object o = ic.lookup(jndiResourceName); if (o != null) { if (o instanceof Properties) { props = (Properties) o; } else { System.err.println("shiftone resource is not java.util.Properites type!!"); } } } catch (NamingException e) { log("Unable to process your jndi properties name. Your proxy will not work" + jndiResourceName, e); } return props; } private void debugProxyRequest(HttpRequest request) { System.out.println("header count -> " + request.getAllHeaders().length); for (Header header : request.getAllHeaders()) { System.out.print("Header name-> " + header.getName() + "\t"); System.out.print("Header value -> " + header.getValue()); System.out.println(); } } }