rrddumpservlet.java

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//
// This file is part of the OpenNMS(R) Application.
//
// OpenNMS(R) is Copyright (C) 2002-2003 The OpenNMS Group, Inc.  All rights reserved.
// OpenNMS(R) is a derivative work, containing both original code, included code and modified
// code that was published under the GNU General Public License. Copyrights for modified 
// and included code are below.
//
// OpenNMS(R) is a registered trademark of The OpenNMS Group, Inc.
//
// Modifications:
//
// 12 Nov 2002: Added response time reports to webUI.
//
// Original coda base Copyright (C) 1999-2001 Oculan Corp.  All rights reserved.
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
//
// For more information contact:
//      OpenNMS Licensing       <[e-mail]>
//      http://www.opennms.org/
//      http://www.opennms.com/
//

package org.opennms.web.response;

import java.io.BufferedReader;
import java.io.File;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.io.StringReader;
import java.io.StringWriter;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.opennms.web.MissingParameterException;
import org.opennms.web.Util;

/**
 * A servlet that creates an XML dump of network performance data using the <a
 * href="http://www.rrdtool.org/">RRDTool </a>.
 * 
 * <p>
 * This servlet executes an <em>rrdtool dump</em> command in another process,
 * piping its XML output to the <code>ServletOutputStream</code>.
 * </p>
 * 
 * @author <A HREF="mailto:[e-mail]">Lawrence Karnowski </A>
 * @author <A HREF="http://www.opennms.org/">OpenNMS </A>
 */
public class RRDDumpServlet extends HttpServlet {
    /**
     * The working directory where we find the RRD files.
     */
    protected String workDir;

    /**
     * The dump command (minus the actual RRD filename).
     */
    protected String commandPrefix;

    /**
     * Initializes this servlet by reading the rrdtool-graph properties file.
     */
    public void init() throws ServletException {
        ServletConfig config = this.getServletConfig();

        this.workDir = config.getInitParameter("rrd-directory");
        this.commandPrefix = config.getInitParameter("rrd-dump-command");

        if (this.workDir == null || this.commandPrefix == null) {
            throw new ServletException("Did not get all required init params. rrd-directory and rrd-dump-command are both required.  Please check your web.xml.");
        }
    }

    /**
     * Checks the parameters passed to this servlet, and if all are okay,
     * executes the RRDTool command in another process and pipes its XML output
     * to the <code>ServletOutputStream</code> back to the requesting web
     * browser.
     */
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String rrd = request.getParameter("rrd");

        if (rrd == null) {
            throw new MissingParameterException("rrd");
        }

        // build the command
        String command = this.commandPrefix + " " + rrd;
        this.log(command);

        // parse the command into an array and fork a process for it
        String[] commandArray = Util.createCommandArray(command, '@');
        Process process = Runtime.getRuntime().exec(commandArray, null, new File(this.workDir));

        PrintWriter out = response.getWriter();
        BufferedReader err = new BufferedReader(new InputStreamReader(process.getErrorStream()));

        if (err.ready()) {
            // get the error message
            StringWriter tempErr = new StringWriter();
            Util.streamToStream(err, tempErr);
            String errorMessage = tempErr.toString();

            // log the error message
            this.log("Read from stderr: " + errorMessage);

            // send the error message to the client
            response.setContentType("text/plain");
            Util.streamToStream(new StringReader(errorMessage), out);
        } else {
            // get the XML output and send it to the client
            BufferedReader in = new BufferedReader(new InputStreamReader(process.getInputStream()));
            response.setContentType("text/xml");
            Util.streamToStream(in, out);
        }

        out.close();
    }

}