source: ComponentRegistry/trunk/ComponentRegistry/src/main/java/clarin/cmdi/componentregistry/frontend/ViewLogPage.java @ 2756

package clarin.cmdi.componentregistry.frontend;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.text.NumberFormat;
import org.apache.log4j.FileAppender;
import org.apache.log4j.Logger;
import org.apache.wicket.PageParameters;
import org.apache.wicket.markup.html.basic.Label;
import org.apache.wicket.markup.html.form.TextArea;
import org.apache.wicket.markup.html.link.DownloadLink;
import org.apache.wicket.markup.html.link.Link;
import org.apache.wicket.model.Model;

/**
 *
 * @author Twan Goosen <twan.goosen@mpi.nl>
 * @author paucas
 */
public class ViewLogPage extends SecureAdminWebPage {

    public ViewLogPage(final PageParameters pageParameters) {
        super(pageParameters);
        addLinks();
        addLogFileContent();
    }

    private void addLinks() {
        add(new Link("home") {
            @Override
            public void onClick() {
                setResponsePage(AdminHomePage.class);
            }
        });
    }

    private void addLogFileContent() {
        final int tailSize = 1000000; // Megabyte

        final NumberFormat numberFormat = NumberFormat.getIntegerInstance();
        numberFormat.setGroupingUsed(true);

        final File logFile = getLogFile();
        if (logFile != null) {
            try {
                final RandomAccessFile raLogFile = geFileTail(logFile, tailSize);
                try {
                    final String content = getLogFileContent(raLogFile);

                    add(new Label("logLabel", String.format("Showing final %s bytes (or less) of total %s in %s:", numberFormat.format(tailSize), numberFormat.format(raLogFile.length()), logFile)));
                    add(new TextArea("logText", new Model(content)));

                    add(new DownloadLink("logDownloadLink", logFile));
                } finally {
                    raLogFile.close();
                }
            } catch (IOException ioEx) {
                add(new Label("logLabel", "Could not read from log file. See error message below."));
                add(new TextArea("logText", new Model(ioEx.getMessage())));
            }
        }
    }

    private String getLogFileContent(final RandomAccessFile randomAccessFile) throws IOException {
        String currentLine;
        StringBuilder contentBuilder = new StringBuilder();
        while ((currentLine = randomAccessFile.readLine()) != null) {
            contentBuilder.append(currentLine).append("\n");
        }
        String content = contentBuilder.toString();
        return content;
    }

    private RandomAccessFile geFileTail(File logFile, int tailLength) throws IOException, FileNotFoundException {
        // Skip to tail of file
        final RandomAccessFile raLogFile = new RandomAccessFile(logFile, "r");
        final long startPosition = raLogFile.length() - tailLength;
        if (startPosition > 0) {
            raLogFile.seek(startPosition);
            // Read until end of line so we don't end up halfway some random line
            raLogFile.readLine();
        }
        return raLogFile;
    }

    private File getLogFile() {
        // Get file from appender
        final FileAppender appender = (FileAppender) Logger.getRootLogger().getAppender("ROOT");
        if (appender != null) {
            return new File(appender.getFile());
        }
        return null;
    }
}