Class FileMessageFactory


  • public class FileMessageFactory
    extends Object
    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.
    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.
    To force a cleanup, call cleanup() from the calling object.
    This class is not thread safe.
    Version:
    1.0
    • Field Detail

      • READ_SIZE

        public static final int READ_SIZE
        The number of bytes that we read from file
        See Also:
        Constant Field Values
      • file

        protected final File file
        The file that we are reading/writing
      • openForWrite

        protected final boolean openForWrite
        True means that we are writing with this factory. False means that we are reading with this factory
      • closed

        protected boolean closed
        Once the factory is used, it cannot be reused.
      • in

        protected FileInputStream in
        When openForWrite=false, the input stream is held by this variable
      • out

        protected FileOutputStream out
        When openForWrite=true, the output stream is held by this variable
      • nrOfMessagesProcessed

        protected int nrOfMessagesProcessed
        The number of messages we have written
      • size

        protected long size
        The total size of the file
      • totalNrOfMessages

        protected long totalNrOfMessages
        The total number of packets that we split this file into
      • lastMessageProcessed

        protected AtomicLong lastMessageProcessed
        The number of the last message processed. Message IDs are 1 based.
      • msgBuffer

        protected final Map<Long,​FileMessage> msgBuffer
        Messages received out of order are held in the buffer until required. If everything is worked as expected, messages will spend very little time in the buffer.
      • data

        protected byte[] data
        The bytes that we hold the data in, not thread safe.
      • isWriting

        protected boolean isWriting
        Flag that indicates if a thread is writing messages to disk. Access to this flag must be synchronised.
      • creationTime

        protected long creationTime
        The time this instance was created. (in milliseconds)
      • maxValidTime

        protected int maxValidTime
        The maximum valid time(in seconds) from creationTime.
    • Method Detail

      • getInstance

        public static FileMessageFactory getInstance​(File f,
                                                     boolean openForWrite)
                                              throws FileNotFoundException,
                                                     IOException
        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.
        Parameters:
        f - File - the file to be read or written
        openForWrite - boolean - true, means we are writing to the file, false means we are reading from it
        Returns:
        FileMessageFactory
        Throws:
        FileNotFoundException - - if the file to be read doesn't exist
        IOException - - if it fails to create the file that is to be written
      • readMessage

        public FileMessage readMessage​(FileMessage f)
                                throws IllegalArgumentException,
                                       IOException
        Reads file data into the file message and sets the size, totalLength, totalNrOfMsgs and the message number
        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. Don't hand off the message to one thread and read the same with another.
        Parameters:
        f - FileMessage - the message to be populated with file data
        Returns:
        FileMessage - returns the same message passed in as a parameter, or null if EOF
        Throws:
        IllegalArgumentException - - if the factory is for writing or is closed
        IOException - - if a file read exception occurs
      • writeMessage

        public boolean writeMessage​(FileMessage msg)
                             throws IllegalArgumentException,
                                    IOException
        Writes a message to file. If (msg.getMessageNumber() == msg.getTotalNrOfMsgs()) the output stream will be closed after writing.
        Parameters:
        msg - FileMessage - message containing data to be written
        Returns:
        returns true if the file is complete and outputstream is closed, false otherwise.
        Throws:
        IllegalArgumentException - - if the factory is opened for read or closed
        IOException - - if a file write error occurs
      • cleanup

        public void cleanup()
        Closes the factory, its streams and sets all its references to null
      • checkState

        protected void checkState​(boolean openForWrite)
                           throws IllegalArgumentException
        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.
        Parameters:
        openForWrite - The value to check
        Throws:
        IllegalArgumentException - if the state is not the expected one
      • getFile

        public File getFile()
      • isValid

        public boolean isValid()
      • getMaxValidTime

        public int getMaxValidTime()
      • setMaxValidTime

        public void setMaxValidTime​(int maxValidTime)