public class

Category

extends Object
implements AppenderAttachable
java.lang.Object
   ↳ org.apache.log4j.Category
Known Direct Subclasses
Known Indirect Subclasses

Class Overview

This class has been deprecated and replaced by the Logger subclass. It will be kept around to preserve backward compatibility until mid 2003.

Logger is a subclass of Category, i.e. it extends Category. In other words, a logger is a category. Thus, all operations that can be performed on a category can be performed on a logger. Internally, whenever log4j is asked to produce a Category object, it will instead produce a Logger object. Log4j 1.2 will never produce Category objects but only Logger instances. In order to preserve backward compatibility, methods that previously accepted category objects still continue to accept category objects.

For example, the following are all legal and will work as expected. 

       // Deprecated form:
       Category cat = Category.getInstance("foo.bar")

       // Preferred form for retrieving loggers:
       Logger logger = Logger.getLogger("foo.bar")

The first form is deprecated and should be avoided.

There is absolutely no need for new client code to use or refer to the Category class. Whenever possible, please avoid referring to it or using it.

See the short manual for an introduction on this class.

See the document entitled preparing for log4j 1.3 for a more detailed discussion.

Summary

Fields
protected boolean additive Additivity is set to true by default, that is children inherit the appenders of their ancestors by default.
protected Level level The assigned level of this category.
protected String name The name of this category.
protected Category parent The parent of this category.
protected LoggerRepository repository
protected ResourceBundle resourceBundle
Protected Constructors
Category(String name)
This constructor created a new Category instance and sets its name.
Public Methods
synchronized void addAppender(Appender newAppender)
Add newAppender to the list of appenders of this Category instance.
void assertLog(boolean assertion, String msg)
If assertion parameter is false, then logs msg as an error statement.
void callAppenders(LoggingEvent event)
Call the appenders in the hierrachy starting at this.
void debug(Object message, Throwable t)
Log a message object with the DEBUG level including the stack trace of the Throwable t passed as parameter.
void debug(Object message)
Log a message object with the DEBUG level.
void error(Object message, Throwable t)
Log a message object with the ERROR level including the stack trace of the Throwable t passed as parameter.
void error(Object message)
Log a message object with the ERROR Level.
static Logger exists(String name)
This method is deprecated. Please use exists(String) instead.
void fatal(Object message)
Log a message object with the FATAL Level.
void fatal(Object message, Throwable t)
Log a message object with the FATAL level including the stack trace of the Throwable t passed as parameter.
boolean getAdditivity()
Get the additivity flag for this Category instance.
synchronized Enumeration getAllAppenders()
Get the appenders contained in this category as an Enumeration.
synchronized Appender getAppender(String name)
Look for the appender named as name.
Priority getChainedPriority()
This method is deprecated. Please use the the getEffectiveLevel() method instead.
static Enumeration getCurrentCategories()
This method is deprecated. Please use getCurrentLoggers() instead.
static LoggerRepository getDefaultHierarchy()
This method is deprecated. Please use getLoggerRepository() instead.
Level getEffectiveLevel()
Starting from this category, search the category hierarchy for a non-null level and return it.
LoggerRepository getHierarchy()
This method is deprecated. Please use getLoggerRepository() instead.
static Category getInstance(String name)
This method is deprecated. Make sure to use getLogger(String) instead.
static Category getInstance(Class clazz)
This method is deprecated. Please make sure to use getLogger(Class) instead.
final Level getLevel()
Returns the assigned Level, if any, for this Category.
LoggerRepository getLoggerRepository()
Return the the LoggerRepository where this Category is attached.
final String getName()
Return the category name.
final Category getParent()
Returns the parent of this category.
final Level getPriority()
This method is deprecated. Please use getLevel() instead.
ResourceBundle getResourceBundle()
Return the inherited ResourceBundle for this category.
final static Category getRoot()
This method is deprecated. Please use getRootLogger() instead.
void info(Object message)
Log a message object with the INFO Level.
void info(Object message, Throwable t)
Log a message object with the INFO level including the stack trace of the Throwable t passed as parameter.
boolean isAttached(Appender appender)
Is the appender passed as parameter attached to this category?
boolean isDebugEnabled()
Check whether this category is enabled for the DEBUG Level.
boolean isEnabledFor(Priority level)
Check whether this category is enabled for a given Level passed as parameter.
boolean isInfoEnabled()
Check whether this category is enabled for the info Level.
void l7dlog(Priority priority, String key, Throwable t)
Log a localized message.
void l7dlog(Priority priority, String key, Object[] params, Throwable t)
Log a localized and parameterized message.
void log(String callerFQCN, Priority level, Object message, Throwable t)
This is the most generic printing method.
void log(Priority priority, Object message, Throwable t)
This generic form is intended to be used by wrappers.
void log(Priority priority, Object message)
This generic form is intended to be used by wrappers.
synchronized void removeAllAppenders()
Remove all previously added appenders from this Category instance.
synchronized void removeAppender(Appender appender)
Remove the appender passed as parameter form the list of appenders.
synchronized void removeAppender(String name)
Remove the appender with the name passed as parameter form the list of appenders.
void setAdditivity(boolean additive)
Set the additivity flag for this Category instance.
void setLevel(Level level)
Set the level of this Category.
void setPriority(Priority priority)
This method is deprecated. Please use setLevel(Level) instead.
void setResourceBundle(ResourceBundle bundle)
Set the resource bundle to be used with localized logging methods l7dlog(Priority, String, Throwable) and l7dlog(Priority, String, Object[], Throwable).
static void shutdown()
This method is deprecated. Please use shutdown() instead.
void warn(Object message, Throwable t)
Log a message with the WARN level including the stack trace of the Throwable t passed as parameter.
void warn(Object message)
Log a message object with the WARN Level.
Protected Methods
void forcedLog(String fqcn, Priority level, Object message, Throwable t)
This method creates a new logging event and logs the event without further checks.
String getResourceBundleString(String key)
Returns the string resource coresponding to key in this category's inherited resource bundle.
[Expand]
Inherited Methods
From class java.lang.Object
From interface org.apache.log4j.spi.AppenderAttachable

Fields

protected boolean additive

Additivity is set to true by default, that is children inherit the appenders of their ancestors by default. If this variable is set to false then the appenders found in the ancestors of this category are not used. However, the children of this category will inherit its appenders, unless the children have their additivity flag set to false too. See the user manual for more details.

protected Level level

The assigned level of this category. The level variable need not be assigned a value in which case it is inherited form the hierarchy.

protected String name

The name of this category.

protected Category parent

The parent of this category. All categories have at least one ancestor which is the root category.

protected LoggerRepository repository

protected ResourceBundle resourceBundle

Protected Constructors

protected Category (String name)

This constructor created a new Category instance and sets its name.

It is intended to be used by sub-classes only. You should not create categories directly.

Parameters
name The name of the category.

Public Methods

public synchronized void addAppender (Appender newAppender)

Add newAppender to the list of appenders of this Category instance.

If newAppender is already in the list of appenders, then it won't be added again.

public void assertLog (boolean assertion, String msg)

If assertion parameter is false, then logs msg as an error statement.

The assert method has been renamed to assertLog because assert is a language reserved word in JDK 1.4.

Parameters
msg The message to print if assertion is false.

public void callAppenders (LoggingEvent event)

Call the appenders in the hierrachy starting at this. If no appenders could be found, emit a warning.

This method calls all the appenders inherited from the hierarchy circumventing any evaluation of whether to log or not to log the particular log request.

Parameters
event the event to log.

public void debug (Object message, Throwable t)

Log a message object with the DEBUG level including the stack trace of the Throwable t passed as parameter.

See debug(Object) form for more detailed information.

Parameters
message the message object to log.
t the exception to log, including its stack trace.

public void debug (Object message)

Log a message object with the DEBUG level.

This method first checks if this category is DEBUG enabled by comparing the level of this category with the DEBUG level. If this category is DEBUG enabled, then it converts the message object (passed as parameter) to a string by invoking the appropriate ObjectRenderer. It then proceeds to call all the registered appenders in this category and also higher in the hierarchy depending on the value of the additivity flag.

WARNING Note that passing a Throwable to this method will print the name of the Throwable but no stack trace. To print a stack trace use the debug(Object, Throwable) form instead.

Parameters
message the message object to log.

public void error (Object message, Throwable t)

Log a message object with the ERROR level including the stack trace of the Throwable t passed as parameter.

See error(Object) form for more detailed information.

Parameters
message the message object to log.
t the exception to log, including its stack trace.

public void error (Object message)

Log a message object with the ERROR Level.

This method first checks if this category is ERROR enabled by comparing the level of this category with ERROR Level. If this category is ERROR enabled, then it converts the message object passed as parameter to a string by invoking the appropriate ObjectRenderer. It proceeds to call all the registered appenders in this category and also higher in the hierarchy depending on the value of the additivity flag.

WARNING Note that passing a Throwable to this method will print the name of the Throwable but no stack trace. To print a stack trace use the error(Object, Throwable) form instead.

Parameters
message the message object to log

public static Logger exists (String name)

This method is deprecated.
Please use exists(String) instead.

If the named category exists (in the default hierarchy) then it returns a reference to the category, otherwise it returns null.

public void fatal (Object message)

Log a message object with the FATAL Level.

This method first checks if this category is FATAL enabled by comparing the level of this category with FATAL Level. If the category is FATAL enabled, then it converts the message object passed as parameter to a string by invoking the appropriate ObjectRenderer. It proceeds to call all the registered appenders in this category and also higher in the hierarchy depending on the value of the additivity flag.

WARNING Note that passing a Throwable to this method will print the name of the Throwable but no stack trace. To print a stack trace use the fatal(Object, Throwable) form instead.

Parameters
message the message object to log

public void fatal (Object message, Throwable t)

Log a message object with the FATAL level including the stack trace of the Throwable t passed as parameter.

See fatal(Object) for more detailed information.

Parameters
message the message object to log.
t the exception to log, including its stack trace.

public boolean getAdditivity ()

Get the additivity flag for this Category instance.

public synchronized Enumeration getAllAppenders ()

Get the appenders contained in this category as an Enumeration. If no appenders can be found, then a NullEnumeration is returned.

Returns
  • Enumeration An enumeration of the appenders in this category.

public synchronized Appender getAppender (String name)

Look for the appender named as name.

Return the appender with that name if in the list. Return null otherwise.

public Priority getChainedPriority ()

This method is deprecated.
Please use the the getEffectiveLevel() method instead.

public static Enumeration getCurrentCategories ()

This method is deprecated.
Please use getCurrentLoggers() instead.

Returns all the currently defined categories in the default hierarchy as an java.util.Enumeration Enumeration.

The root category is not included in the returned Enumeration.

public static LoggerRepository getDefaultHierarchy ()

This method is deprecated.
Please use getLoggerRepository() instead.

Return the default Hierarchy instance.

public Level getEffectiveLevel ()

Starting from this category, search the category hierarchy for a non-null level and return it. Otherwise, return the level of the root category.

The Category class is designed so that this method executes as quickly as possible.

public LoggerRepository getHierarchy ()

This method is deprecated.
Please use getLoggerRepository() instead.

Return the the Hierarchy where this Category instance is attached.

public static Category getInstance (String name)

This method is deprecated.
Make sure to use getLogger(String) instead.

public static Category getInstance (Class clazz)

This method is deprecated.
Please make sure to use getLogger(Class) instead.

public final Level getLevel ()

Returns the assigned Level, if any, for this Category.

Returns
  • Level - the assigned Level, can be null.

public LoggerRepository getLoggerRepository ()

Return the the LoggerRepository where this Category is attached.

public final String getName ()

Return the category name.

public final Category getParent ()

Returns the parent of this category. Note that the parent of a given category may change during the lifetime of the category.

The root category will return null.

public final Level getPriority ()

This method is deprecated.
Please use getLevel() instead.

public ResourceBundle getResourceBundle ()

Return the inherited ResourceBundle for this category.

This method walks the hierarchy to find the appropriate resource bundle. It will return the resource bundle attached to the closest ancestor of this category, much like the way priorities are searched. In case there is no bundle in the hierarchy then null is returned.

public static final Category getRoot ()

This method is deprecated.
Please use getRootLogger() instead.

public void info (Object message)

Log a message object with the INFO Level.

This method first checks if this category is INFO enabled by comparing the level of this category with INFO Level. If the category is INFO enabled, then it converts the message object passed as parameter to a string by invoking the appropriate ObjectRenderer. It proceeds to call all the registered appenders in this category and also higher in the hierarchy depending on the value of the additivity flag.

WARNING Note that passing a Throwable to this method will print the name of the Throwable but no stack trace. To print a stack trace use the info(Object, Throwable) form instead.

Parameters
message the message object to log

public void info (Object message, Throwable t)

Log a message object with the INFO level including the stack trace of the Throwable t passed as parameter.

See info(Object) for more detailed information.

Parameters
message the message object to log.
t the exception to log, including its stack trace.

public boolean isAttached (Appender appender)

Is the appender passed as parameter attached to this category?

public boolean isDebugEnabled ()

Check whether this category is enabled for the DEBUG Level.

This function is intended to lessen the computational cost of disabled log debug statements.

For some cat Category object, when you write, 

      cat.debug("This is entry number: " + i );

You incur the cost constructing the message, concatenatiion in this case, regardless of whether the message is logged or not.

If you are worried about speed, then you should write 

 	 if(cat.isDebugEnabled()) {
 	   cat.debug("This is entry number: " + i );
 	 }

This way you will not incur the cost of parameter construction if debugging is disabled for cat. On the other hand, if the cat is debug enabled, you will incur the cost of evaluating whether the category is debug enabled twice. Once in isDebugEnabled and once in the debug. This is an insignificant overhead since evaluating a category takes about 1%% of the time it takes to actually log.

Returns
  • boolean - true if this category is debug enabled, false otherwise.

public boolean isEnabledFor (Priority level)

Check whether this category is enabled for a given Level passed as parameter. See also isDebugEnabled().

Returns
  • boolean True if this category is enabled for level.

public boolean isInfoEnabled ()

Check whether this category is enabled for the info Level. See also isDebugEnabled().

Returns
  • boolean - true if this category is enabled for level info, false otherwise.

public void l7dlog (Priority priority, String key, Throwable t)

Log a localized message. The user supplied parameter key is replaced by its localized version from the resource bundle.

See Also

public void l7dlog (Priority priority, String key, Object[] params, Throwable t)

Log a localized and parameterized message. First, the user supplied key is searched in the resource bundle. Next, the resulting pattern is formatted using format(String, Object[]) method with the user supplied object array params.

public void log (String callerFQCN, Priority level, Object message, Throwable t)

This is the most generic printing method. It is intended to be invoked by wrapper classes.

Parameters
callerFQCN The wrapper class' fully qualified class name.
level The level of the logging request.
message The message of the logging request.
t The throwable of the logging request, may be null.

public void log (Priority priority, Object message, Throwable t)

This generic form is intended to be used by wrappers.

public void log (Priority priority, Object message)

This generic form is intended to be used by wrappers.

public synchronized void removeAllAppenders ()

Remove all previously added appenders from this Category instance.

This is useful when re-reading configuration information.

public synchronized void removeAppender (Appender appender)

Remove the appender passed as parameter form the list of appenders.

public synchronized void removeAppender (String name)

Remove the appender with the name passed as parameter form the list of appenders.

public void setAdditivity (boolean additive)

Set the additivity flag for this Category instance.

public void setLevel (Level level)

Set the level of this Category. If you are passing any of Level.DEBUG, Level.INFO, Level.WARN, Level.ERROR, Level.FATAL as a parameter, you need to case them as Level.

As in 

    logger.setLevel((Level) Level.DEBUG);

Null values are admitted.

public void setPriority (Priority priority)

This method is deprecated.
Please use setLevel(Level) instead.

Set the level of this Category.

Null values are admitted.

public void setResourceBundle (ResourceBundle bundle)

Set the resource bundle to be used with localized logging methods l7dlog(Priority, String, Throwable) and l7dlog(Priority, String, Object[], Throwable).

public static void shutdown ()

This method is deprecated.
Please use shutdown() instead.

Calling this method will safely close and remove all appenders in all the categories including root contained in the default hierachy.

Some appenders such as SocketAppender and AsyncAppender need to be closed before the application exists. Otherwise, pending logging events might be lost.

The shutdown method is careful to close nested appenders before closing regular appenders. This is allows configurations where a regular appender is attached to a category and again to a nested appender.

public void warn (Object message, Throwable t)

Log a message with the WARN level including the stack trace of the Throwable t passed as parameter.

See warn(Object) for more detailed information.

Parameters
message the message object to log.
t the exception to log, including its stack trace.

public void warn (Object message)

Log a message object with the WARN Level.

This method first checks if this category is WARN enabled by comparing the level of this category with WARN Level. If the category is WARN enabled, then it converts the message object passed as parameter to a string by invoking the appropriate ObjectRenderer. It proceeds to call all the registered appenders in this category and also higher in the hieararchy depending on the value of the additivity flag.

WARNING Note that passing a Throwable to this method will print the name of the Throwable but no stack trace. To print a stack trace use the warn(Object, Throwable) form instead.

Parameters
message the message object to log.

Protected Methods

protected void forcedLog (String fqcn, Priority level, Object message, Throwable t)

This method creates a new logging event and logs the event without further checks.

protected String getResourceBundleString (String key)

Returns the string resource coresponding to key in this category's inherited resource bundle. See also getResourceBundle().

If the resource cannot be found, then an error message will be logged complaining about the missing resource.