com.gargoylesoftware.base.trace

Class Trace

java.lang.Object

com.gargoylesoftware.base.trace.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 and Description
static class	Trace.WhereAmIException An exception used to determine where the code is at any point in time.

Field Summary

Fields

Modifier and Type	Field and Description
static TraceChannel	err The equivilent of "standard error"
private static java.lang.String	LINE_SEPARATOR
static TraceChannel	out The equivilent of "standard out"
private static TraceController	TRACE_CONTROLLER
private static TraceItemDispatcher	TRACE_ITEM_DISPATCHER

Constructor Summary

Constructors

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

Method Summary

Modifier and Type	Method and 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(java.lang.String string) Print a line to the default channel If the channel is null then nothing will be printed.
static void	print(TraceChannel channel, java.lang.String string) Print a line to the specified channel.
static void	printLines(java.lang.String[] lines) Print the specified lines to the default trace channel.
static void	printLines(TraceChannel channel, java.lang.String[] lines) Print the specified lines to the trace channel.
static void	println(java.lang.String string) Print the line to the default channel with a new line at the end.
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	printStackTrace(java.lang.Throwable throwable) Print the stack trace to the default channel.
static void	printStackTrace(TraceChannel channel, java.lang.Throwable throwable) Print the stack trace to the specified 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

TRACE_ITEM_DISPATCHER

private static final TraceItemDispatcher TRACE_ITEM_DISPATCHER

TRACE_CONTROLLER

private static final TraceController TRACE_CONTROLLER

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.

getDispatcher

static TraceItemDispatcher getDispatcher()

Returns:

The dispatcher

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