001 /**
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements. See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership. The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License. You may obtain a copy of the License at
009 *
010 * http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018 package org.apache.hadoop.conf;
019
020 import java.io.IOException;
021 import java.io.OutputStreamWriter;
022 import java.io.Writer;
023
024 import javax.servlet.ServletException;
025 import javax.servlet.http.HttpServlet;
026 import javax.servlet.http.HttpServletRequest;
027 import javax.servlet.http.HttpServletResponse;
028
029 import org.apache.hadoop.classification.InterfaceAudience;
030 import org.apache.hadoop.classification.InterfaceStability;
031 import org.apache.hadoop.http.HttpServer;
032
033 /**
034 * A servlet to print out the running configuration data.
035 */
036 @InterfaceAudience.LimitedPrivate({"HDFS", "MapReduce"})
037 @InterfaceStability.Unstable
038 public class ConfServlet extends HttpServlet {
039 private static final long serialVersionUID = 1L;
040
041 private static final String FORMAT_JSON = "json";
042 private static final String FORMAT_XML = "xml";
043 private static final String FORMAT_PARAM = "format";
044
045 /**
046 * Return the Configuration of the daemon hosting this servlet.
047 * This is populated when the HttpServer starts.
048 */
049 private Configuration getConfFromContext() {
050 Configuration conf = (Configuration)getServletContext().getAttribute(
051 HttpServer.CONF_CONTEXT_ATTRIBUTE);
052 assert conf != null;
053 return conf;
054 }
055
056 @Override
057 public void doGet(HttpServletRequest request, HttpServletResponse response)
058 throws ServletException, IOException {
059
060 // Do the authorization
061 if (!HttpServer.hasAdministratorAccess(getServletContext(), request,
062 response)) {
063 return;
064 }
065
066 String format = request.getParameter(FORMAT_PARAM);
067 if (null == format) {
068 format = FORMAT_XML;
069 }
070
071 if (FORMAT_XML.equals(format)) {
072 response.setContentType("text/xml; charset=utf-8");
073 } else if (FORMAT_JSON.equals(format)) {
074 response.setContentType("application/json; charset=utf-8");
075 }
076
077 Writer out = response.getWriter();
078 try {
079 writeResponse(getConfFromContext(), out, format);
080 } catch (BadFormatException bfe) {
081 response.sendError(HttpServletResponse.SC_BAD_REQUEST, bfe.getMessage());
082 }
083 out.close();
084 }
085
086 /**
087 * Guts of the servlet - extracted for easy testing.
088 */
089 static void writeResponse(Configuration conf, Writer out, String format)
090 throws IOException, BadFormatException {
091 if (FORMAT_JSON.equals(format)) {
092 Configuration.dumpConfiguration(conf, out);
093 } else if (FORMAT_XML.equals(format)) {
094 conf.writeXml(out);
095 } else {
096 throw new BadFormatException("Bad format: " + format);
097 }
098 }
099
100 public static class BadFormatException extends Exception {
101 private static final long serialVersionUID = 1L;
102
103 public BadFormatException(String msg) {
104 super(msg);
105 }
106 }
107
108 }