Package com.gargoylesoftware.base.trace

Class Trace

  • public class Trace
extends java.lang.Object
    A class that provides a mechanism for logging diagnostic messages. This mechanism is significantly faster then calling System.out.println directly as the printing is done on a background thread which does not impact the performance of the application threads.

    The methods for tracing are print(String), println(String) and printStackTrace(Throwable). The basic idea is that we want the trace methods to return to the working threads as quickly as possible so we put the thing to be traced on a queue. The queue is then processed by a second thread which performs all the formatting and actual output.

    Trace can be configured using the TraceController class - see getController(). It is possible to redirect System.out and System.err so that calling System.out.println("foo") will be the same as calling Trace.println("foo") 

     Trace.getController().setOutRedirected(true);
 Trace.getController().setErrRedirected(true);
    Calls to any of the print methods will print to a TraceChannel which in turn will print using whatever TraceWriters have been added to it. Print methods that do not take a TraceChannel will use the default channel - see TraceController.setDefaultChannel(TraceChannel)

    If you are using this code in a JVM prior to 1.3 then you need to read this:
    Because trace lines are being processed on a second thread, there might still be trace messages in the queue when the VM exits. To solve this problem we introduce the method exit(int) which will shut down the second thread and then call System.exit(). If you are running on a java 1.3 VM or higher then it is not neccessary to call exit(int) as Trace will automatically install a shutdown hook which will do the neccessary cleanup.

    Version:
    $Revision: 1.6 $

    • Nested Class Summary

      Nested Classes 
      Modifier and Type Class Description
      static class  Trace.WhereAmIException
      An exception used to determine where the code is at any point in time.

    • Constructor Summary

      Constructors 
      Modifier Constructor Description
      private Trace()
      Private constructor to prevent instantiation of this class.

    • Method Summary

      All Methods Static Methods Concrete Methods 
      Modifier and Type Method Description
      protected static void assertNotNull​(java.lang.String fieldName, java.lang.Object fieldValue)
      Verify that the specified value is not null.
      static void exit​(int statusCode)
      Shutdown all buffering and exit the VM with the specified status code.
      static void flush()
      Flush the trace queue.
      static TraceController getController()
      Return the controller object for the debugging stuff
      (package private) static TraceItemDispatcher getDispatcher()  
      static void print​(TraceChannel channel, java.lang.String string)
      Print a line to the specified channel.
      static void print​(java.lang.String string)
      Print a line to the default channel If the channel is null then nothing will be printed.
      static void printLines​(TraceChannel channel, java.lang.String[] lines)
      Print the specified lines to the trace channel.
      static void printLines​(java.lang.String[] lines)
      Print the specified lines to the default trace channel.
      static void println​(TraceChannel channel, java.lang.String string)
      Print the line to the specified channel with a new line at the end.
      static void println​(java.lang.String string)
      Print the line to the default channel with a new line at the end.
      static void printStackTrace​(TraceChannel channel, java.lang.Throwable throwable)
      Print the stack trace to the specified channel.
      static void printStackTrace​(java.lang.Throwable throwable)
      Print the stack trace to the default channel.
      static java.lang.String throwableToString​(java.lang.Throwable t)
      Dump the stack trace from the specified throwable into a String.
      static java.lang.String[] throwableToStringArray​(java.lang.Throwable t)
      Dump the stack trace from the specified throwable into an array of strings where each line in the trace is a separate string.
      static void whereAmI()
      Print a stack trace to show where we came from.
      static void whereAmI​(TraceChannel channel)
      Print a stack trace to show where we came from.

      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    • Field Detail

      • out

        public static final TraceChannel out
        The equivilent of "standard out"

      • err

        public static final TraceChannel err
        The equivilent of "standard error"

      • LINE_SEPARATOR

        private static final java.lang.String LINE_SEPARATOR

    • Constructor Detail

      • Trace

        private Trace()
        Private constructor to prevent instantiation of this class.

    • Method Detail

      • print

        public static void print​(TraceChannel channel,
                         java.lang.String string)
        Print a line to the specified channel. If the channel is null then nothing will be printed.
        Parameters:
        channel - The trace channel to use
        string - The text string to write.

      • print

        public static void print​(java.lang.String string)
        Print a line to the default channel If the channel is null then nothing will be printed.
        Parameters:
        string - The text string to write.

      • println

        public static void println​(TraceChannel channel,
                           java.lang.String string)
        Print the line to the specified channel with a new line at the end. If the channel is null then nothing will be printed.
        Parameters:
        channel - The trace channel to use
        string - the string to write.

      • println

        public static void println​(java.lang.String string)
        Print the line to the default channel with a new line at the end.
        Parameters:
        string - the string to write.

      • printStackTrace

        public static void printStackTrace​(TraceChannel channel,
                                   java.lang.Throwable throwable)
        Print the stack trace to the specified channel. If the channel is null then nothing will be printed.
        Parameters:
        channel - The trace channel to use
        throwable - The exception to print

      • printStackTrace

        public static void printStackTrace​(java.lang.Throwable throwable)
        Print the stack trace to the default channel.
        Parameters:
        throwable - The exception to print.

      • printLines

        public static void printLines​(java.lang.String[] lines)
        Print the specified lines to the default trace channel.
        Parameters:
        lines - The lines to print.

      • printLines

        public static void printLines​(TraceChannel channel,
                              java.lang.String[] lines)
        Print the specified lines to the trace channel. If the channel is null then nothing will be printed.
        Parameters:
        channel - The trace channel to use
        lines - the lines to print.

      • whereAmI

        public static void whereAmI()
        Print a stack trace to show where we came from. It will be printed to the default channel.

      • whereAmI

        public static void whereAmI​(TraceChannel channel)
        Print a stack trace to show where we came from. If the channel is null then nothing will be printed.
        Parameters:
        channel - The trace channel to use.

      • throwableToStringArray

        public static java.lang.String[] throwableToStringArray​(java.lang.Throwable t)
        Dump the stack trace from the specified throwable into an array of strings where each line in the trace is a separate string. Additionally, expand all tabs to spaces.
        Parameters:
        t - The exception.
        Returns:
        The resulting string.

      • throwableToString

        public static java.lang.String throwableToString​(java.lang.Throwable t)
        Dump the stack trace from the specified throwable into a String.
        Parameters:
        t - The exception.
        Returns:
        The resulting string.

      • getController

        public static TraceController getController()
        Return the controller object for the debugging stuff
        Returns:
        The controller in use.

      • flush

        public static void flush()
        Flush the trace queue.

      • exit

        public static void exit​(int statusCode)
        Shutdown all buffering and exit the VM with the specified status code.

        Note This is no longer needed if you are running JDK1.3 or higher as we now register a shutdown hook to disable buffering before the VM exits.

        Parameters:
        statusCode - The status code returned when the application exits.

      • assertNotNull

        protected static final void assertNotNull​(java.lang.String fieldName,
                                          java.lang.Object fieldValue)
                                   throws DetailedNullPointerException
        Verify that the specified value is not null. If it is then throw an exception
        Parameters:
        fieldName - The name of the field to check
        fieldValue - The value of the field to check
        Throws:
        DetailedNullPointerException - If fieldValue is null