cmsrfsfileviewer.java

一个cms内容管理平台

/*
 * File   : $Source: /usr/local/cvs/opencms/src/org/opencms/util/CmsRfsFileViewer.java,v $
 * Date   : $Date: 2006/11/23 16:59:38 $
 * Version: $Revision: 1.19 $
 *
 * This library is part of OpenCms -
 * the Open Source Content Mananagement System
 *
 * Copyright (c) 2005 Alkacon Software GmbH (http://www.alkacon.com)
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * For further information about Alkacon Software GmbH, please see the
 * company website: http://www.alkacon.com
 *
 * For further information about OpenCms, please see the
 * project website: http://www.opencms.org
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

package org.opencms.util;

import org.opencms.i18n.CmsEncoder;
import org.opencms.main.CmsIllegalArgumentException;
import org.opencms.main.CmsLog;
import org.opencms.main.CmsRuntimeException;
import org.opencms.main.OpenCms;

import java.io.BufferedReader;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.LineNumberReader;
import java.io.OutputStreamWriter;
import java.nio.charset.Charset;
import java.nio.charset.IllegalCharsetNameException;
import java.nio.charset.UnsupportedCharsetException;
import java.util.HashMap;
import java.util.Map;
import java.util.Stack;

import org.apache.commons.logging.Log;

/**
 * The representation of a RFS file along with the settings to provide 
 * access to certain portions (amount of lines) of it. <p> 
 *  
 * Most often the underlying file will be the OpenCms logfile. <p>
 * 
 * The portion of the file that is shown is defined by a "window" of "windowSize" lines of text 
 * at a position "windowPosition" which is an enumeration of windows in ascending order. <p>
 * 
 * @author  Achim Westermann 
 * 
 * @version $Revision: 1.19 $ 
 * 
 * @since 6.0.0 
 */
public class CmsRfsFileViewer implements Cloneable {

    /** The log object for this class. */
    protected static final Log LOG = CmsLog.getLog(CmsRfsFileViewer.class);

    /** Decides whethter the view onto the underlying file via readFilePortion is enabled. */
    private boolean m_enabled;

    /** The character encoding of the underlying file. */
    private Charset m_fileEncoding;

    /** Maps file paths to internal info instances. */
    protected Map m_fileName2lineIndex;

    /** The path to the underlying file. */
    protected String m_filePath;

    /** 
     * If value is <code>true</code>, all setter methods will throw a 
     * <code>{@link CmsRuntimeException}</code><p>. 
     * 
     * Only the method <code>{@link #clone()}</code> returns a clone that has set this 
     * member to <code>false</code> allowing modification to take place.<p>
     */
    private boolean m_frozen;

    /** 
     * If true the represented file is a standard OpenCms log file and may be displayed 
     * in more convenient ways (in future versions) because the format is known. 
     */
    private boolean m_isLogfile;

    /** The current window (numbered from zero to amount of possible different windows).  */
    protected int m_windowPos;

    /** The amount of lines to show. */
    protected int m_windowSize;

    /**
     * Creates an instance with default settings that tries to use the log file path obtained 
     * from <code>{@link OpenCms}'s {@link org.opencms.main.CmsSystemInfo}</code> instance.<p>
     * 
     * If the log file path is invalid or not configured correctly a logging is performed and the 
     * path remains empty to allow user-specified file selection.<p>
     */
    public CmsRfsFileViewer() {

        m_isLogfile = true;
        m_fileName2lineIndex = new HashMap();
        // system default charset: see http://java.sun.com/j2se/corejava/intl/reference/faqs/index.html#default-encoding
        m_fileEncoding = Charset.forName(new OutputStreamWriter(new ByteArrayOutputStream()).getEncoding());
        m_enabled = true;
        m_windowSize = 200;

    }

    /**
     * Internal helper that throws a <code>{@link CmsRuntimeException}</code> if the 
     * configuration of this instance has been frozen ({@link #setFrozen(boolean)}).<p>
     * 
     * @throws CmsRuntimeException if the configuration of this instance has been frozen 
     *                             ({@link #setFrozen(boolean)})
     */
    private void checkFrozen() throws CmsRuntimeException {

        if (m_frozen) {
            throw new CmsRuntimeException(Messages.get().container(Messages.ERR_FILE_VIEW_SETTINGS_FROZEN_0));
        }
    }

    /**
     * Returns a clone of this file view settings that is not "frozen" and therefore allows modifications.<p>
     * 
     * Every instance that plans to modify settings has to obtain a clone first that may be 
     * modified. The original instance returned from  
     * (<code>{@link org.opencms.workplace.CmsWorkplaceManager#getFileViewSettings()}</code>) will throw 
     * a <code>{@link CmsRuntimeException}</code> for each setter invocation. <p>
     * 
     * @return a clone of this file view settings that is not "frozen" and therefore allows modifications
     */
    public Object clone() {

        // first run after installation: filePath is null:
        if (m_filePath == null) {
            // below that runlevel the following call  will fail (not initialized from config yet):
            if (OpenCms.getRunLevel() >= OpenCms.RUNLEVEL_3_SHELL_ACCESS) {
                m_filePath = OpenCms.getSystemInfo().getLogFileRfsPath();
            }
        }
        CmsRfsFileViewer clone = new CmsRfsFileViewer();
        try {
            // strings are immutable: no outside modification possible.
            clone.setFilePath(m_filePath);
        } catch (CmsRfsException e) {
            // will never happen because m_filePath was verified in setFilePath of this instance.
        } catch (CmsRuntimeException e) {
            // will never happen because m_filePath was verified in setFilePath of this instance.
        }
        clone.m_fileEncoding = m_fileEncoding;
        clone.m_isLogfile = m_isLogfile;
        clone.m_enabled = m_enabled;
        //clone.m_windowPos = m_windowPos;
        clone.setWindowSize(m_windowSize);
        clone.m_fileName2lineIndex = m_fileName2lineIndex;
        // allow clone-modifications. 
        clone.m_frozen = false;
        return clone;
    }

    /**
     * Returns the canonical name of the character encoding of the underlying file.<p>
     * 
     * If no special choice is fed into 
     * <code>{@link #setFileEncoding(String)}</code> before this call 
     * always the system default character encoding is returned.<p>
     * 
     * This value may be ignored outside and will be ignored inside if the 
     * underlying does not contain textual content.<p>
     * 
     * @return the canonical name of the character encoding of the underlying file
     */
    public String getFileEncoding() {

        return m_fileEncoding.name();
    }

    /**
     * Returns the path denoting the file that is accessed.<p>
     * 
     * @return the path denoting the file that is accessed
     */
    public String getFilePath() {

        return m_filePath;
    }

    /**
     * Returns true if the view's internal file path points to a log file in standard OpenCms format.<p> 
     * 
     * @return true if the view's internal file path points to a log file in standard OpenCms format
     */
    public boolean getIsLogfile() {

        // method name is bean-convention of apache.commons.beanutils (unlike eclipse's convention for booleans)
        return m_isLogfile;
    }

    /**
     * Returns the start position of the current display.<p>
     * 
     * This is a count of "windows" that 
     * consist of viewable text with "windowSize" lines of text (for a non-standard log file) or 
     * log-entries (for a standard log file).<p>
     * 
     * @return the start position of the current display
     */
    public int getWindowPos() {

        return m_windowPos;
    }

    /**
     * Get the amount of lines (or entries depending on wether a standard log file is shown) 
     * to display per page. <p>
     * 
     * @return the amount of lines to display per page
     */
    public int getWindowSize() {

        return m_windowSize;
    }

    /**
     * Returns true if this view upon the underlying file via 
     * <code>{@link #readFilePortion()}</code> is enabled.<p>
     * 
     * 
     * @return true if this view upon the underlying file via 
     * <code>{@link #readFilePortion()}</code> is enabled.<p>
     */
    public boolean isEnabled() {

        return m_enabled;
    }

    /**
     * Return the view portion of lines of text from the underlying file or an 
     * empty String if <code>{@link #isEnabled()}</code> returns <code>false</code>.<p>
     * 
     * @return the view portion of lines of text from the underlying file or an 
     *         empty String if <code>{@link #isEnabled()}</code> returns <code>false</code>
     * @throws CmsRfsException if something goes wrong
     */
    public String readFilePortion() throws CmsRfsException {

        if (m_enabled) {
            // if we want to view the logfile we have to set the internal m_windowPos to the last window 
            // to view the end: 
            int lines = -1;
            int startLine;
            if (m_isLogfile) {
                lines = scrollToFileEnd();
                // for logfile mode we show the last window of window size: 
                // it could be possible that only 4 lines are in the last window 
                // (e.g.: 123 lines with windowsize 10 -> last window has 3 lines) 
                // so we ignore the window semantics and show the n last lines: 
                startLine = lines - m_windowSize;
            } else {
                m_windowPos = 0;
                startLine = m_windowPos * m_windowSize;
            }
            LineNumberReader reader = null;
            try {
                // don't make the buffer too big, just big enough for windowSize lines (estimation: avg. of 200 characters per line) 
                // to save reading too much (this optimizes to read the first windows, much later windows will be slower...)
                reader = new LineNumberReader(new BufferedReader(new InputStreamReader(
                    new FileInputStream(m_filePath),
                    m_fileEncoding)), (int)m_windowSize * 200);
                int currentLine = 0;
                // skip the lines to the current window:
                while (startLine > currentLine) {
                    reader.readLine();
                    currentLine++;
                }
                StringBuffer result = new StringBuffer();
                String read = reader.readLine();

                // logfile treatment is different
                // we invert the lines: latest come first