java.util.logging
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. If properties are not defined (or have invalid values) then the specified default values are used.

• java.util.logging.MemoryHandler.level specifies the level for the Handler (defaults to Level.ALL).
• java.util.logging.MemoryHandler.filter specifies the name of a Filter class to use (defaults to no Filter).
• java.util.logging.MemoryHandler.size defines the buffer size (defaults to 1000).
• java.util.logging.MemoryHandler.push defines the pushLevel (defaults to level.SEVERE).
• java.util.logging.MemoryHandler.target specifies the name of the target Handler class. (no default).

Since:

1.4

Field Summary

private LogRecord[]	buffer
(package private) int	count
private static int	DEFAULT_SIZE
private Level	pushLevel
private int	size
(package private) int	start
private Handler	target

Fields inherited from class java.util.logging.Handler

sealed

Constructor Summary

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

MemoryHandler(Handler target, int size, Level pushLevel)
Create a MemoryHandler.

Method Summary

void	close() Close the Handler and free all associated resources.
private void	configure()
void	flush() Causes a flush on the target Handler.
Level	getPushLevel() Get the pushLevel.
private void	init()
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 inherited from class java.util.logging.Handler

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

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_SIZE

private static final int DEFAULT_SIZE

See Also:

Constant Field Values

pushLevel

private Level pushLevel

size

private int size

target

private Handler target

buffer

private LogRecord[] buffer

start

int start

count

int count

Constructor Detail

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 - is size is <= 0

Method Detail

configure

private void configure()

init

private void init()

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

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()
           throws SecurityException

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

Specified by:

close in class Handler

Throws:

SecurityException - if a security manager exists and if the caller does not have LoggingPermission("control").

setPushLevel

public void setPushLevel(Level newLevel)
                  throws SecurityException

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

Throws:

SecurityException - if a security manager exists and if the caller does not have LoggingPermission("control").

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.

Overrides:

isLoggable in class Handler

Parameters:

record - a LogRecord

Returns:

true if the LogRecord would be logged.