com.googlecode.psiprobe.controllers.logs.FollowController.java Source code

Introduction

Here is the source code for com.googlecode.psiprobe.controllers.logs.FollowController.java

Source

/*
 * Licensed under the GPL License.  You may not use this file except in
 * compliance with the License.  You may obtain a copy of the License at
 *
 *     http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
 *
 * THIS PACKAGE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
 * MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */
package com.googlecode.psiprobe.controllers.logs;

import com.googlecode.psiprobe.tools.BackwardsFileStream;
import com.googlecode.psiprobe.tools.BackwardsLineReader;
import com.googlecode.psiprobe.tools.logging.LogDestination;
import java.io.File;
import java.util.LinkedList;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.springframework.web.bind.ServletRequestUtils;
import org.springframework.web.servlet.ModelAndView;

/**
 * 
 * @author Vlad Ilyushchenko
 * @author Mark Lewis
 */
public class FollowController extends LogHandlerController {

    protected ModelAndView handleLogFile(HttpServletRequest request, HttpServletResponse response,
            LogDestination logDest) throws Exception {

        ModelAndView mv = new ModelAndView(getViewName());
        File file = logDest.getFile();

        if (file.exists()) {
            LinkedList lines = new LinkedList();
            long actualLength = file.length();
            long lastKnownLength = ServletRequestUtils.getLongParameter(request, "lastKnownLength", 0);
            long currentLength = ServletRequestUtils.getLongParameter(request, "currentLength", actualLength);
            long maxReadLines = ServletRequestUtils.getLongParameter(request, "maxReadLines", 0);

            if (lastKnownLength > currentLength || lastKnownLength > actualLength || currentLength > actualLength) {
                //
                // file length got reset
                //
                lastKnownLength = 0;
                lines.add(" ------------- THE FILE HAS BEEN TRUNCATED --------------");
            }

            BackwardsFileStream bfs = new BackwardsFileStream(file, currentLength);
            try {
                BackwardsLineReader br = new BackwardsLineReader(bfs);
                long readSize = 0;
                long totalReadSize = currentLength - lastKnownLength;
                String s;
                while (readSize < totalReadSize && (s = br.readLine()) != null) {
                    if (!s.equals("")) {
                        lines.addFirst(s);
                        readSize += s.length();
                    } else {
                        readSize++;
                    }
                    if (maxReadLines != 0 && lines.size() >= maxReadLines) {
                        break;
                    }
                }

                if (lastKnownLength != 0 && readSize > totalReadSize) {
                    lines.removeFirst();
                }
            } finally {
                bfs.close();
            }

            mv.addObject("lines", lines);
        }
        return mv;
    }

}