org.apache.log4j
Class Category

java.lang.Object
  org.apache.log4j.Category

All Implemented Interfaces:

AppenderAttachable

Direct Known Subclasses:

Logger

public class Category

extends Object

implements AppenderAttachable

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. Whenever log4j is asked to produce a Category object, it will instead produce a Logger object. However, 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.

name

protected String name

The name of this category.

level

protected volatile 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.

parent

protected volatile Category parent

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

resourceBundle

protected ResourceBundle resourceBundle

repository

protected LoggerRepository repository

additive

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.

Category

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.

addAppender

public 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.

Specified by:

addAppender in interface AppenderAttachable

assertLog

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:

assertion -

msg - The message to print if assertion is false.

Since:

1.2

callAppenders

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.

debug

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.

debug

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.

error

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

error

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.

exists

public static Logger exists(String name)

Deprecated. Please use LogManager.exists(java.lang.String) instead.

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

fatal

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

fatal

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.

forcedLog

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.

getAdditivity

public boolean getAdditivity()

Get the additivity flag for this Category instance.

getAllAppenders

public Enumeration getAllAppenders()

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

Specified by:

getAllAppenders in interface AppenderAttachable

Returns:

Enumeration An enumeration of the appenders in this category.

getAppender

public Appender getAppender(String name)

Look for the appender named as name.

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

Specified by:

getAppender in interface AppenderAttachable

getEffectiveLevel

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.

getChainedPriority

public Priority getChainedPriority()

Deprecated. Please use the the getEffectiveLevel() method instead.

getCurrentCategories

public static Enumeration getCurrentCategories()

Deprecated. Please use LogManager.getCurrentLoggers() instead.

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

The root category is not included in the returned Enumeration.

getDefaultHierarchy

public static LoggerRepository getDefaultHierarchy()

Deprecated. Please use LogManager.getLoggerRepository() instead.

Return the default Hierarchy instance.

Since:

1.0

getHierarchy

public LoggerRepository getHierarchy()

Deprecated. Please use getLoggerRepository() instead.

Return the the Hierarchy where this Category instance is attached.

Since:

1.1

getLoggerRepository

public LoggerRepository getLoggerRepository()

Return the the LoggerRepository where this Category is attached.

Since:

1.2

getInstance

public static Category getInstance(String name)

Retrieve a category with named as the name parameter. If the named category already exists, then the existing instance will be reutrned. Otherwise, a new instance is created. By default, categories do not have a set level but inherit it from the hierarchy. This is one of the central features of log4j. Deprecated Please use Logger.getLogger(String) instead.

Parameters:

name - The name of the category to retrieve.

getInstance

public static Category getInstance(Class clazz)

Shorthand for getInstance(clazz.getName()).

Parameters:

clazz - The name of clazz will be used as the name of the category to retrieve. See getInstance(String) for more detailed information. Deprecated Please use Logger.getLogger(Class) instead.

Since:

1.0

getName

public final String getName()

Return the category name.

getParent

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.

Since:

1.2

getLevel

public final Level getLevel()

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

Returns:

Level - the assigned Level, can be null.

getPriority

public final Level getPriority()

Deprecated. Please use getLevel() instead.

getRoot

public static final Category getRoot()

Return the root of the default category hierrachy.

The root category is always instantiated and available. It's name is "root".

Nevertheless, calling Category.getInstance("root") does not retrieve the root category but a category just under root named "root". Deprecated Use Logger.getRootLogger() instead.

getResourceBundle

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.

Since:

0.9.0

getResourceBundleString

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.

info

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

info

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.

isAttached

public boolean isAttached(Appender appender)

Is the appender passed as parameter attached to this category?

Specified by:

isAttached in interface AppenderAttachable

isDebugEnabled

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.

isEnabledFor

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.

isInfoEnabled

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.

l7dlog

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.

Since:

0.8.4

See Also:

setResourceBundle(java.util.ResourceBundle)

l7dlog

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 MessageFormat.format(String,Object[]) method with the user supplied object array params.

Since:

0.8.4

log

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

This generic form is intended to be used by wrappers.

log

public void log(Priority priority,
                Object message)

This generic form is intended to be used by wrappers.

log

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.

removeAllAppenders

public void removeAllAppenders()

Remove all previously added appenders from this Category instance.

This is useful when re-reading configuration information.

Specified by:

removeAllAppenders in interface AppenderAttachable

removeAppender

public void removeAppender(Appender appender)

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

Specified by:

removeAppender in interface AppenderAttachable

Since:

0.8.2

removeAppender

public void removeAppender(String name)

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

Specified by:

removeAppender in interface AppenderAttachable

Since:

0.8.2

setAdditivity

public void setAdditivity(boolean additive)

Set the additivity flag for this Category instance.

Since:

0.8.1

setLevel

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.

setPriority

public void setPriority(Priority priority)

Deprecated. Please use setLevel(org.apache.log4j.Level) instead.

Set the level of this Category.

Null values are admitted.

setResourceBundle

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).

Since:

0.8.4

shutdown

public static void shutdown()

Deprecated. Please use LogManager.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.

Since:

1.0

warn

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.

warn

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.