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//---PACKAGE DECLARATION--- |
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package uk.ac.ukc.iscream.core.loggers; |
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|
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//---IMPORTS--- |
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import uk.ac.ukc.iscream.util.*; |
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import uk.ac.ukc.iscream.core.*; |
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import java.util.Date; |
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import java.text.DateFormat; |
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import java.util.Locale; |
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import java.io.BufferedWriter; |
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import java.io.File; |
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import java.io.FileWriter; |
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import java.io.IOException; |
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|
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/** |
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* The FileLogger is an implementation of the LoggerImpl defined |
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* in the associated interface. It provides quite extensive features to allow |
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* logging ot a text file. |
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* |
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* @author $Author: ajm4 $ |
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* @version $Id: FileLogger.java,v 1.2 2000/11/29 21:27:25 ajm4 Exp $ |
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*/ |
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class FileLogger implements LoggerImpl { |
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|
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//---FINAL ATTRIBUTES--- |
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|
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/** |
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* The current CVS revision of this class |
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*/ |
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public final String REVISION = "$Revision: 1.2 $"; |
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|
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//---STATIC METHODS--- |
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|
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//---CONSTRUCTORS--- |
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|
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/** |
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* Creates a new FileLogger. |
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* |
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* The constructor checks that writing will be ok, then sets up the |
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* writer. It makes use of the fileCheck() method found later on to |
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* ensure writing will be ok, and throws an IOException if there is |
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* a problem. Errors at this stage cannot be logged because the |
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* logging mechanism has not be setup completely, so any problems |
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* are printed to the screen in the same format used for logging. |
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* |
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* @throws IOException if there is a problem with the file check. |
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*/ |
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public FileLogger() throws IOException{ |
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_verbosityLevel = Integer.parseInt(System.getProperty("uk.ac.ukc.iscream.Verbosity")); |
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filename = System.getProperty("uk.ac.ukc.iscream.LoggerClass.FileLogger.filename"); |
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// Perform file check to make sure writing is ok |
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if(!fileCheck()){ |
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// Have to system.out.println errors because logging mechanism failed ! |
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System.out.println(formatLogLine(this.toString(), "File check failed, construction terminated")); |
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throw new IOException("File check failed, unable to create FileLog"); |
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} |
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try{ |
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// Setup the writer |
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writer = new BufferedWriter(new FileWriter(filename, true)); |
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// File is now open |
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open = true; |
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} |
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catch(IOException e){ |
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System.out.println(formatLogLine(toString(), "Attempt to setup writer failed - " + e.getMessage())); |
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} |
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// Put an initial line into the log |
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write(toString(), Logger.SYSINIT, "started"); |
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write(toString(), Logger.SYSMSG, "using verbosity " + _verbosityLevel); |
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} |
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|
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//---PUBLIC METHODS--- |
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|
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/** |
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* The write() method writes a line of log to the file, prepending |
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* it with some information about where to line came from and the |
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* date. This formatting is handled by the formatLogLine() method. |
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* There is some synchronisation here due to problems with the logfiles |
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* having multiple lines written on the same line, followed by dotted |
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* newlines in the wrong places. This is due to this method being |
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* called by multiple threads. |
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* |
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* @param source A string representation of the calling object. |
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* @param message The message to be logged. |
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*/ |
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public synchronized void write(String source, int verbosity, String message) { |
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// Check to make sure file is open |
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if(open){ |
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// Produce a nicely formatted line for the logfile |
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String line = formatLogLine(source, message); |
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try{ |
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// We have to synchronize here due to problems with two write()'s being called before a newLine() |
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synchronized(writer){ |
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// Attempt to write the line |
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writer.write(line); |
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// Best to use newLine() as it will use the correct platform encoding |
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writer.newLine(); |
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} |
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// Make sure the line is written immeidiately |
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writer.flush(); |
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} |
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catch(IOException e){ |
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// We'd best log the error |
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System.out.println(formatLogLine(this.toString(), "Writing to logfile failed - " + e.getMessage())); |
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// As it's an IOException we should suspend logging |
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open = false; |
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} |
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} |
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else{ |
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// If file is not open we should print this to the screen |
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System.out.println(formatLogLine(this.toString(), "Write failed - file not open")); |
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} |
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} |
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|
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/** |
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* The clear() method erases the contents of the logfile. It does |
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* this in a very clumsy way - by closing the writer and opening a |
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* new one which is set not to append. This results in the logfile |
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* being overwritten, which effectively erases it. |
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*/ |
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public void clear(){ |
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// Check file is open |
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if(open){ |
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write(toString(), Logger.SYSMSG, "Attempting to clear logfile"); |
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try{ |
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// Close appending writer |
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open = false; |
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writer.close(); |
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// Open a non-appending writer |
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writer = new BufferedWriter(new FileWriter(filename)); |
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open = true; |
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} |
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catch(IOException e){ |
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// We'd best log the error |
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write(toString(), Logger.ERROR, "Attempt to clear logfile failed - "+e.getMessage()); |
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// As it's an IOException we should suspend logging |
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open = false; |
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} |
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} |
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else{ |
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// If file is not open we should print this to the screen |
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System.out.println(formatLogLine(toString(), "Clearing failed - file not open")); |
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} |
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} |
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|
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/** |
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* The close() method closes the logfile and no more data can be written. |
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* If writing is attempted after close() has been called an error will be |
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* generated. The open() method can be used to reopen or open a new file. |
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*/ |
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public void close(){ |
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// Check to see if a file is open |
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if(open){ |
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write(toString(), Logger.SYSMSG, "Attempting to terminate logging"); |
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try{ |
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open = false; |
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writer.close(); |
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} |
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catch(IOException e){ |
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write(toString(), Logger.ERROR, "Attempt to close logfile failed - " + e.getMessage()); |
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// As it's an IOException we should suspend logging |
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open = false; |
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} |
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} |
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else{ |
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// If file is not open we should print this to the screen |
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System.out.println(formatLogLine(toString(), "Close failed - file not open")); |
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} |
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} |
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|
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/** |
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* The open() method opens a new file after the close() method has |
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* been called on the FileLog. This enables the user to easily change |
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* the file to which the log is being written. An error is generated |
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* if a file is already open. |
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* |
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* @param filename The new file to write to. |
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* @throws IOException if the file cannot be written to. |
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*/ |
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public void open(String filename) throws IOException{ |
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// Check to see if a file is open |
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if(open){ |
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// If file is already open then we should log that this went wrong |
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write(this.toString(), Logger.WARNING, "Open failed - a file is already open"); |
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} |
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else{ |
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this.filename = filename; |
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if(!fileCheck()) { |
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// Have to system.out.println errors because logging mechanism failed ! |
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System.out.println(formatLogLine(toString(), "File check failed, construction terminated")); |
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throw new IOException("File check failed, unable to create FileLog"); |
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} |
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try{ |
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// Setup the writer |
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writer = new BufferedWriter(new FileWriter(filename, true)); |
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// File is now open |
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open = true; |
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} |
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catch(IOException e){ |
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System.out.println(formatLogLine(toString(), "Attempt to open writer failed - " + e.getMessage())); |
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} |
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} |
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} |
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|
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/** |
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* The suspend() method halts writing to the file by setting the open |
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* boolean to false, and thus blocking the write() method. A line is |
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* written to the logfile beforehand to note that writing has been |
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* suspended. |
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*/ |
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public void suspend(){ |
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// Check to see if a file is open |
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if(open){ |
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// Make a note of the fact that writing has been suspended |
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write(toString(), Logger.SYSMSG, "Writing suspended"); |
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// Make sure writing not permitted |
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open=false; |
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} |
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else{ |
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// If file is not open we should print this to the screen |
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System.out.println(formatLogLine(toString(), "Suspend failed - file not open")); |
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} |
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} |
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|
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/** |
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* The resume() method resumes writing to the file by setting the open |
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* boolean to true. A line is written to the logfile to signify this |
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* event occuring. |
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*/ |
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public void resume(){ |
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// Check to see if a file is open |
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if(open){ |
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// If file is open we should print this to the screen |
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System.out.println(formatLogLine(toString(), "Resume failed - file open")); |
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} |
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else{ |
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// Permit writing again |
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open=true; |
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// Make a note of the fact that writing has been resumed |
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write(toString(), Logger.SYSMSG, "Writing resumed"); |
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} |
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} |
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|
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/** |
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* Overrides the {@link java.lang.Object#toString() Object.toString()} |
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* method to provide clean logging (every class should have this). |
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* |
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* This uses the uk.ac.ukc.iscream.util.FormatName class |
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* to format the toString() |
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* |
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* @return the name of this class and its CVS revision |
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*/ |
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public String toString() { |
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return FormatName.getName( |
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_name, |
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getClass().getName(), |
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REVISION); |
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} |
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|
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//---PRIVATE METHODS--- |
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|
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/** |
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* This method generates a nicely formatted line for the log, |
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* including the date/time and the source of the message. The date |
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* and time are formatted using the DateFormat class, and the source |
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* class is formatted using the toString() method found in every |
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* source file. This is then prepended to the message and returned. |
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* |
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* @param source A string representation of the calling object. |
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* @param message The message to be logged. |
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* @return The string to be written to the log. |
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*/ |
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private String formatLogLine(String source, String message){ |
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String date = DateFormat.getDateTimeInstance(DateFormat.SHORT, DateFormat.MEDIUM).format(new Date()); |
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return "[" + date + "] " + source + ": " + message; |
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} |
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|
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/** |
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* The fileCheck() method is used to ensure that writing is ok. It |
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* performs so basic checks to make sure that if the file exists |
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* it can be written to, and if not a new file is created. A boolean |
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* result is returned to signify success or failure. |
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* |
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* @return A boolean value signify whether the test was sucessful. |
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*/ |
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private boolean fileCheck(){ |
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boolean fileOK = false; |
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try{ |
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File file = new File(filename); |
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|
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// File already exists |
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if(file.exists()) { |
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/* Only want success if it is a file (not a directory) |
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* and can be written to. |
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*/ |
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if(file.isFile() && file.canWrite()) { |
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fileOK = true; |
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} |
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} |
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// Create a new file and suceed |
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else{ |
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file.createNewFile(); |
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fileOK = true; |
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} |
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} |
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catch(IOException e){ |
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System.out.println(formatLogLine(toString(), "File check failed - "+e.getMessage())); |
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} |
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|
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return fileOK; |
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} |
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|
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//---ACCESSOR/MUTATOR METHODS--- |
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|
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//---ATTRIBUTES--- |
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|
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/** |
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* The filename of the currently open, or last open, file. |
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*/ |
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private String filename; |
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|
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/** |
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* The verbosity level of this instance |
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*/ |
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private int _verbosityLevel; |
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|
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/** |
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* A reference to the writer being used. |
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*/ |
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private BufferedWriter writer; |
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|
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/** |
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* A boolean signifying whether a file is open or not. |
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*/ |
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private boolean open = false; |
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|
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/** |
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* This is the friendly identifier of the |
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* component this class is running in. |
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* eg, a Filter may be called "filter1", |
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* If this class does not have an owning |
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* component, a name from the configuration |
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* can be placed here. This name could also |
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* be changed to null for utility classes. |
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*/ |
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private String _name = Core.NAME; |
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|
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//---STATIC ATTRIBUTES--- |
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|
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} |