psiprobe.controllers.logs.FollowController.java Source code

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

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/**
 * 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 psiprobe.controllers.logs;

import org.springframework.web.bind.ServletRequestUtils;
import org.springframework.web.servlet.ModelAndView;

import psiprobe.tools.BackwardsFileStream;
import psiprobe.tools.BackwardsLineReader;
import psiprobe.tools.logging.LogDestination;

import java.io.File;
import java.util.LinkedList;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

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

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

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

        if (file.exists()) {
            LinkedList<String> 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 --------------");
            }

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

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

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

}