com.redhat.rhn.common.util.FileUtils.java Source code

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Here is the source code for com.redhat.rhn.common.util.FileUtils.java

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/**
 * Copyright (c) 2009--2010 Red Hat, Inc.
 *
 * This software is licensed to you under the GNU General Public License,
 * version 2 (GPLv2). There is NO WARRANTY for this software, express or
 * implied, including the implied warranties of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE. You should have received a copy of GPLv2
 * along with this software; if not, see
 * http://www.gnu.org/licenses/old-licenses/gpl-2.0.txt.
 *
 * Red Hat trademarks are not licensed under GPLv2. No permission is
 * granted to use or replicate Red Hat trademarks that are incorporated
 * in this software or its documentation.
 */
package com.redhat.rhn.common.util;

import org.apache.commons.collections.buffer.CircularFifoBuffer;
import org.apache.commons.io.LineIterator;
import org.apache.log4j.Logger;
import org.jfree.io.IOUtils;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.StringWriter;
import java.io.Writer;

/**
 * Simple file utilities to read/write strings to a file on disk.
 *
 *@version $Rev$
 */
public class FileUtils {

    private static Logger log = Logger.getLogger(FileUtils.class);

    private FileUtils() {
    }

    /**
     * Save a String to a file on disk using specified path.
     *
     * WARNING:  This deletes the original file before it writes.
     *
     * @param contents to save to file on disk
     * @param path to save file to.
     */
    public static void writeStringToFile(String contents, String path) {
        try {
            File file = new File(path);
            if (file.exists()) {
                file.delete();
            }
            file.createNewFile();
            Writer output = new BufferedWriter(new FileWriter(file));
            try {
                output.write(contents);
            } finally {
                output.close();
            }
        } catch (Exception e) {
            log.error("Error trying to write file to disk: [" + path + "]", e);
            throw new RuntimeException(e);
        }
    }

    /**
     * Read a file off disk into a String and return it.
     *
     * Expect weird stuff if the file is not textual.
     *
     * @param path of file to read in
     * @return String containing file.
     */
    public static String readStringFromFile(String path) {
        log.debug("readStringFromFile: " + path);

        File f = new File(path);
        BufferedReader input;
        try {
            input = new BufferedReader(new FileReader(f));
            StringWriter writer = new StringWriter();
            IOUtils.getInstance().copyWriter(input, writer);
            String contents = writer.toString();
            if (log.isDebugEnabled()) {
                log.debug("contents: " + contents);
            }
            return contents;
        } catch (FileNotFoundException e) {
            throw new RuntimeException("File not found: " + path);
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }

    /**
     * Read a file off disk into a byte array with specified range
     *
     * This can use lots of memory if you read a large file
     *
     * @param fileToRead File to read part of into byte array
     * @param start index of read
     * @param end index of read
     * @return byte[] array from file.
     */
    public static byte[] readByteArrayFromFile(File fileToRead, long start, long end) {
        log.debug("readByteArrayFromFile: " + fileToRead.getAbsolutePath() + " start: " + start + " end: " + end);

        int size = (int) (end - start);
        log.debug("size of array: " + size);
        // Create the byte array to hold the data
        byte[] bytes = new byte[size];
        InputStream is = null;
        try {
            is = new FileInputStream(fileToRead);
            // Read in the bytes
            int offset = 0;
            int numRead = 0;
            // Skip ahead
            is.skip(start);
            // start reading
            while (offset < bytes.length && (numRead) >= 0) {
                numRead = is.read(bytes, offset, bytes.length - offset);
                offset += numRead;
            }
        } catch (FileNotFoundException fnf) {
            log.error("Could not read from: " + fileToRead.getAbsolutePath());
            throw new RuntimeException(fnf);
        } catch (IOException e) {
            log.error("Could not read from: " + fileToRead.getAbsolutePath());
            throw new RuntimeException(e);

        } finally {
            if (is != null) {
                try {
                    is.close();
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
        }
        return bytes;
    }

    /**
     * Reads and returns the last n lines from a given file as string.
     * @param pathToFile path to file
     * @param lines size of the tail
     * @return tail of file as string
     */
    public static String getTailOfFile(String pathToFile, Integer lines) {
        InputStream fileStream = null;
        CircularFifoBuffer buffer = new CircularFifoBuffer(lines);
        try {
            fileStream = new FileInputStream(pathToFile);
            LineIterator it = org.apache.commons.io.IOUtils.lineIterator(fileStream, (String) null);
            while (it.hasNext()) {
                buffer.add(it.nextLine());
            }
        } catch (FileNotFoundException e) {
            log.error("File not found: " + pathToFile);
            throw new RuntimeException(e);
        } catch (IOException e) {
            log.error("Could not read from: " + pathToFile);
            throw new RuntimeException(e);
        } finally {
            org.apache.commons.io.IOUtils.closeQuietly(fileStream);
        }
        // Construct a string from the buffered lines
        StringBuilder sb = new StringBuilder();
        for (Object s : buffer) {
            sb.append(s);
            sb.append(System.getProperty("line.separator"));
        }
        return sb.toString();
    }
}