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
MemoryHandlerwould 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 and 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
All Methods Instance Methods Concrete Methods Modifier and Type Method and Description voidclose()Close the Handler and free all associated resources.voidflush()Causes a flush on the target Handler.LevelgetPushLevel()Get the pushLevel.booleanisLoggable(LogRecord record)Check if this Handler would actually log a given LogRecord into its internal buffer.voidpublish(LogRecord record)Store a LogRecord in an internal buffer.voidpush()Push any buffered output to the target Handler.voidsetPushLevel(Level newLevel)Set the pushLevel.-
Methods inherited from class java.util.logging.Handler
getEncoding, getErrorManager, getFilter, getFormatter, getLevel, reportError, setEncoding, setErrorManager, setFilter, setFormatter, setLevel
-
-
-
-
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- ifsize is <= 0
-
Method Detail
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.
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".
close
public void close() throws SecurityExceptionClose the Handler and free all associated resources. This will also close the target Handler.- Specified by:
-
closein classHandler - 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. It will return false if the LogRecord is null.
- Overrides:
-
isLoggablein classHandler - Parameters:
-
record- a LogRecord - Returns:
- true if the LogRecord would be logged.
-
Submit a bug or feature
For further API reference and developer documentation, see Java SE Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.
Copyright © 1993, 2022, Oracle and/or its affiliates. All rights reserved. Use is subject to license terms. Also see the documentation redistribution policy.
