Class MemoryHandler

java.lang.Object

java.util.logging.Handler

java.util.logging.MemoryHandler

public class MemoryHandler
extends Handler

Handler that buffers requests in a circular buffer in memory.

Normally this Handler simply stores incoming LogRecords into its memory buffer and discards earlier records. This buffering is very cheap and avoids formatting costs. On certain trigger conditions, the MemoryHandler will push out its current buffer contents to a target Handler, which will typically publish them to the outside world.

There are three main models for triggering a push of the buffer:

• An incoming LogRecord has a type that is greater than a pre-defined level, the pushLevel.
• An external class calls the push method explicitly.
• A subclass overrides the log method and scans each incoming LogRecord and calls push if a record matches some desired criteria.

Configuration: By default each MemoryHandler is initialized using the following LogManager configuration properties where <handler-name> refers to the fully-qualified class name of the handler. If properties are not defined (or have invalid values) then the specified default values are used. If no default value is defined then a RuntimeException is thrown.

• <handler-name>.level specifies the level for the Handler (defaults to Level.ALL).
• <handler-name>.filter specifies the name of a Filter class to use (defaults to no Filter).
• <handler-name>.size defines the buffer size (defaults to 1000).
• <handler-name>.push defines the pushLevel (defaults to level.SEVERE).
• <handler-name>.target specifies the name of the target Handler class. (no default).

For example, the properties for MemoryHandler would be:

• java.util.logging.MemoryHandler.level=INFO
• java.util.logging.MemoryHandler.formatter=java.util.logging.SimpleFormatter

For a custom handler, e.g. com.foo.MyHandler, the properties would be:

• com.foo.MyHandler.level=INFO
• com.foo.MyHandler.formatter=java.util.logging.SimpleFormatter

Since:

1.4

Constructor Summary

Constructors

Constructor	Description
MemoryHandler()	Create a MemoryHandler and configure it based on LogManager configuration properties.
MemoryHandler(Handler target, int size, Level pushLevel)	Create a MemoryHandler.

Method Summary

Modifier and Type	Method	Description
void	close()	Close the Handler and free all associated resources.
void	flush()	Causes a flush on the target Handler.
Level	getPushLevel()	Get the pushLevel.
boolean	isLoggable(LogRecord record)	Check if this Handler would actually log a given LogRecord into its internal buffer.
void	publish(LogRecord record)	Store a LogRecord in an internal buffer.
void	push()	Push any buffered output to the target Handler.
void	setPushLevel(Level newLevel)	Set the pushLevel.

Methods declared in class Handler

getEncoding, getErrorManager, getFilter, getFormatter, getLevel, reportError, setEncoding, setErrorManager, setFilter, setFormatter, setLevel

Modifier and Type	Method	Description
String	getEncoding()	Return the character encoding for this Handler.
ErrorManager	getErrorManager()	Retrieves the ErrorManager for this Handler.
Filter	getFilter()	Get the current Filter for this Handler.
Formatter	getFormatter()	Return the Formatter for this Handler.
Level	getLevel()	Get the log level specifying which messages will be logged by this Handler.
protected void	reportError(String msg, Exception ex, int code)	Protected convenience method to report an error to this Handler's ErrorManager.
void	setEncoding(String encoding)	Set the character encoding used by this Handler.
void	setErrorManager(ErrorManager em)	Define an ErrorManager for this Handler.
void	setFilter(Filter newFilter)	Set a Filter to control output on this Handler.
void	setFormatter(Formatter newFormatter)	Set a Formatter.
void	setLevel(Level newLevel)	Set the log level specifying which message levels will be logged by this Handler.

Methods declared in class Object

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

Modifier and Type	Method	Description
protected Object	clone()	Answers a new instance of the same class as the receiver, whose slots have been filled in with the values in the slots of the receiver.
boolean	equals(Object o)	Compares the argument to the receiver, and answers true if they represent the same object using a class specific comparison.
protected void	finalize()	Deprecated, for removal: This API element is subject to removal in a future version. May cause performance issues, deadlocks and hangs.
final Class<? extends Object>	getClass()	Answers the unique instance of java.lang.Class which represents the class of the receiver.
int	hashCode()	Answers an integer hash code for the receiver.
final void	notify()	Causes one thread which is waiting on the receiver to be made ready to run.
final void	notifyAll()	Causes all threads which are waiting on the receiver to be made ready to run.
String	toString()	Answers a string containing a concise, human-readable description of the receiver.
final void	wait()	Causes the thread which sent this message to be made not ready to run pending some change in the receiver (as indicated by notify or notifyAll).
final void	wait(long time)	Causes the thread which sent this message to be made not ready to run either pending some change in the receiver (as indicated by notify or notifyAll) or the expiration of the timeout.
final void	wait(long time, int frac)	Causes the thread which sent this message to be made not ready to run either pending some change in the receiver (as indicated by notify or notifyAll) or the expiration of the timeout.

Constructor Details

MemoryHandler

public MemoryHandler()

Create a MemoryHandler and configure it based on LogManager configuration properties.

MemoryHandler

public MemoryHandler(Handler target,
 int size,
 Level pushLevel)

Create a MemoryHandler.

The MemoryHandler is configured based on LogManager properties (or their default values) except that the given pushLevel argument and buffer size argument are used.

Parameters:

target - the Handler to which to publish output.

size - the number of log records to buffer (must be greater than zero)

pushLevel - message level to push on

Throws:

IllegalArgumentException - if size is <= 0

Method Details

publish

public void publish(LogRecord record)

Store a LogRecord in an internal buffer.

If there is a Filter, its isLoggable method is called to check if the given log record is loggable. If not we return. Otherwise the given record is copied into an internal circular buffer. Then the record's level property is compared with the pushLevel. If the given level is greater than or equal to the pushLevel then push is called to write all buffered records to the target output Handler.

Specified by:

publish in class Handler

Parameters:

record - description of the log event. A null record is silently ignored and is not published

push

public void push()

Push any buffered output to the target Handler.

The buffer is then cleared.

flush

public void flush()

Causes a flush on the target Handler.

Note that the current contents of the MemoryHandler buffer are not written out. That requires a "push".

Specified by:

flush in class Handler

close

public void close()

Close the Handler and free all associated resources. This will also close the target Handler.

Specified by:

close in class Handler

setPushLevel

public void setPushLevel(Level newLevel)

Set the pushLevel. After a LogRecord is copied into our internal buffer, if its level is greater than or equal to the pushLevel, then push will be called.

Parameters:

newLevel - the new value of the pushLevel

getPushLevel

public Level getPushLevel()

Get the pushLevel.

Returns:

the value of the pushLevel

isLoggable

public boolean isLoggable(LogRecord record)

Check if this Handler would actually log a given LogRecord into its internal buffer.

This method checks if the LogRecord has an appropriate level and whether it satisfies any Filter. However it does not check whether the LogRecord would result in a "push" of the buffer contents. It will return false if the LogRecord is null.

Overrides:

isLoggable in class Handler

Parameters:

record - a LogRecord (may be null).

Returns:

true if the LogRecord would be logged.