Tomcat example source code file (FileMessageFactory.java)

This example Tomcat source code file (FileMessageFactory.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Tomcat tags/keywords

can't, exception, file, file, fileinputstream, filemessage, filemessagefactory, filemessagefactory, fileoutputstream, illegalargumentexception, illegalargumentexception, io, ioexception, ioexception, message

The Tomcat FileMessageFactory.java source code

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.catalina.ha.deploy;

import java.io.File;
import java.io.IOException;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.FileNotFoundException;

/**
 * This factory is used to read files and write files by splitting them up into
 * smaller messages. So that entire files don't have to be read into memory.
 * <BR>
 * The factory can be used as a reader or writer but not both at the same time.
 * When done reading or writing the factory will close the input or output
 * streams and mark the factory as closed. It is not possible to use it after
 * that. <BR>
 * To force a cleanup, call cleanup() from the calling object. <BR>
 * This class is not thread safe.
 * 
 * @author Filip Hanik
 * @version 1.0
 */
public class FileMessageFactory {
    /*--Static Variables----------------------------------------*/
    public static org.apache.juli.logging.Log log = org.apache.juli.logging.LogFactory
            .getLog(FileMessageFactory.class);

    /**
     * The number of bytes that we read from file
     */
    public static final int READ_SIZE = 1024 * 10; //10kb

    /**
     * The file that we are reading/writing
     */
    protected File file = null;

    /**
     * True means that we are writing with this factory. False means that we are
     * reading with this factory
     */
    protected boolean openForWrite;

    /**
     * Once the factory is used, it can not be reused.
     */
    protected boolean closed = false;

    /**
     * When openForWrite=false, the input stream is held by this variable
     */
    protected FileInputStream in;

    /**
     * When openForWrite=true, the output stream is held by this variable
     */
    protected FileOutputStream out;

    /**
     * The number of messages we have read or written
     */
    protected int nrOfMessagesProcessed = 0;

    /**
     * The total size of the file
     */
    protected long size = 0;

    /**
     * The total number of packets that we split this file into
     */
    protected long totalNrOfMessages = 0;

    /**
     * The bytes that we hold the data in, not thread safe.
     */
    protected byte[] data = new byte[READ_SIZE];

    /**
     * Private constructor, either instantiates a factory to read or write. <BR>
     * When openForWrite==true, then a the file, f, will be created and an
     * output stream is opened to write to it. <BR>
     * When openForWrite==false, an input stream is opened, the file has to
     * exist.
     * 
     * @param f
     *            File - the file to be read/written
     * @param openForWrite
     *            boolean - true means we are writing to the file, false means
     *            we are reading from the file
     * @throws FileNotFoundException -
     *             if the file to be read doesn't exist
     * @throws IOException -
     *             if the system fails to open input/output streams to the file
     *             or if it fails to create the file to be written to.
     */
    private FileMessageFactory(File f, boolean openForWrite)
            throws FileNotFoundException, IOException {
        this.file = f;
        this.openForWrite = openForWrite;
        if (log.isDebugEnabled())
            log.debug("open file " + f + " write " + openForWrite);
        if (openForWrite) {
            if (!file.exists())
                file.createNewFile();
            out = new FileOutputStream(f);
        } else {
            size = file.length();
            totalNrOfMessages = (size / READ_SIZE) + 1;
            in = new FileInputStream(f);
        }//end if

    }

    /**
     * Creates a factory to read or write from a file. When opening for read,
     * the readMessage can be invoked, and when opening for write the
     * writeMessage can be invoked.
     * 
     * @param f
     *            File - the file to be read or written
     * @param openForWrite
     *            boolean - true, means we are writing to the file, false means
     *            we are reading from it
     * @throws FileNotFoundException -
     *             if the file to be read doesn't exist
     * @throws IOException -
     *             if it fails to create the file that is to be written
     * @return FileMessageFactory
     */
    public static FileMessageFactory getInstance(File f, boolean openForWrite)
            throws FileNotFoundException, IOException {
        return new FileMessageFactory(f, openForWrite);
    }

    /**
     * Reads file data into the file message and sets the size, totalLength,
     * totalNrOfMsgs and the message number <BR>
     * If EOF is reached, the factory returns null, and closes itself, otherwise
     * the same message is returned as was passed in. This makes sure that not
     * more memory is ever used. To remember, neither the file message or the
     * factory are thread safe. dont hand off the message to one thread and read
     * the same with another.
     * 
     * @param f
     *            FileMessage - the message to be populated with file data
     * @throws IllegalArgumentException -
     *             if the factory is for writing or is closed
     * @throws IOException -
     *             if a file read exception occurs
     * @return FileMessage - returns the same message passed in as a parameter,
     *         or null if EOF
     */
    public FileMessage readMessage(FileMessage f)
            throws IllegalArgumentException, IOException {
        checkState(false);
        int length = in.read(data);
        if (length == -1) {
            cleanup();
            return null;
        } else {
            f.setData(data, length);
            f.setTotalLength(size);
            f.setTotalNrOfMsgs(totalNrOfMessages);
            f.setMessageNumber(++nrOfMessagesProcessed);
            return f;
        }//end if
    }

    /**
     * Writes a message to file. If (msg.getMessageNumber() ==
     * msg.getTotalNrOfMsgs()) the output stream will be closed after writing.
     * 
     * @param msg
     *            FileMessage - message containing data to be written
     * @throws IllegalArgumentException -
     *             if the factory is opened for read or closed
     * @throws IOException -
     *             if a file write error occurs
     * @return returns true if the file is complete and outputstream is closed,
     *         false otherwise.
     */
    public boolean writeMessage(FileMessage msg)
            throws IllegalArgumentException, IOException {
        if (!openForWrite)
            throw new IllegalArgumentException(
                    "Can't write message, this factory is reading.");
        if (log.isDebugEnabled())
            log.debug("Message " + msg + " data " + msg.getData()
                    + " data length " + msg.getDataLength() + " out " + out);
        if (out != null) {
            out.write(msg.getData(), 0, msg.getDataLength());
            nrOfMessagesProcessed++;
            out.flush();
            if (msg.getMessageNumber() == msg.getTotalNrOfMsgs()) {
                out.close();
                cleanup();
                return true;
            }//end if
        } else {
            if (log.isWarnEnabled())
                log.warn("Receive Message again -- Sender ActTimeout to short [ path: "
                                + msg.getContextPath()
                                + " war: "
                                + msg.getFileName()
                                + " data: "
                                + msg.getData()
                                + " data length: " + msg.getDataLength() + " ]");
        }
        return false;
    }//writeMessage

    /**
     * Closes the factory, its streams and sets all its references to null
     */
    public void cleanup() {
        if (in != null)
            try {
                in.close();
            } catch (Exception ignore) {
            }
        if (out != null)
            try {
                out.close();
            } catch (Exception ignore) {
            }
        in = null;
        out = null;
        size = 0;
        closed = true;
        data = null;
        nrOfMessagesProcessed = 0;
        totalNrOfMessages = 0;
    }

    /**
     * Check to make sure the factory is able to perform the function it is
     * asked to do. Invoked by readMessage/writeMessage before those methods
     * proceed.
     * 
     * @param openForWrite
     *            boolean
     * @throws IllegalArgumentException
     */
    protected void checkState(boolean openForWrite)
            throws IllegalArgumentException {
        if (this.openForWrite != openForWrite) {
            cleanup();
            if (openForWrite)
                throw new IllegalArgumentException(
                        "Can't write message, this factory is reading.");
            else
                throw new IllegalArgumentException(
                        "Can't read message, this factory is writing.");
        }
        if (this.closed) {
            cleanup();
            throw new IllegalArgumentException("Factory has been closed.");
        }
    }

    /**
     * Example usage.
     * 
     * @param args
     *            String[], args[0] - read from filename, args[1] write to
     *            filename
     * @throws Exception
     */
    public static void main(String[] args) throws Exception {

        System.out
                .println("Usage: FileMessageFactory fileToBeRead fileToBeWritten");
        System.out
                .println("Usage: This will make a copy of the file on the local file system");
        FileMessageFactory read = getInstance(new File(args[0]), false);
        FileMessageFactory write = getInstance(new File(args[1]), true);
        FileMessage msg = new FileMessage(null, args[0], args[0]);
        msg = read.readMessage(msg);
        System.out.println("Expecting to write " + msg.getTotalNrOfMsgs()
                + " messages.");
        int cnt = 0;
        while (msg != null) {
            write.writeMessage(msg);
            cnt++;
            msg = read.readMessage(msg);
        }//while
        System.out.println("Actually wrote " + cnt + " messages.");
    }///main

    public File getFile() {
        return file;
    }

}