- java.lang.Object
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- java.util.logging.Handler
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- java.util.logging.MemoryHandler
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public class MemoryHandler extends Handler
Handlerthat buffers requests in a circular buffer in memory.Normally this
Handlersimply stores incomingLogRecordsinto its memory buffer and discards earlier records. This buffering is very cheap and avoids formatting costs. On certain trigger conditions, theMemoryHandlerwill push out its current buffer contents to a targetHandler, which will typically publish them to the outside world.There are three main models for triggering a push of the buffer:
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An incoming
LogRecordhas a type that is greater than a pre-defined level, thepushLevel. -
An external class calls the
pushmethod explicitly. -
A subclass overrides the
logmethod and scans each incomingLogRecordand callspushif a record matches some desired criteria.
Configuration: By default each
MemoryHandleris initialized using the followingLogManagerconfiguration 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 toLevel.ALL). - <handler-name>.filter
specifies the name of a
Filterclass to use (defaults to noFilter). - <handler-name>.size defines the buffer size (defaults to 1000).
- <handler-name>.push
defines the
pushLevel(defaults tolevel.SEVERE). - <handler-name>.target
specifies the name of the target
Handlerclass. (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
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An incoming
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Constructor Summary
Constructors Constructor Description MemoryHandler()Create aMemoryHandlerand configure it based onLogManagerconfiguration properties.MemoryHandler(Handler target, int size, Level pushLevel)Create aMemoryHandler.
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description voidclose()Close theHandlerand free all associated resources.voidflush()Causes a flush on the targetHandler.LevelgetPushLevel()Get thepushLevel.booleanisLoggable(LogRecord record)Check if thisHandlerwould actually log a givenLogRecordinto its internal buffer.voidpublish(LogRecord record)Store aLogRecordin an internal buffer.voidpush()Push any buffered output to the targetHandler.voidsetPushLevel(Level newLevel)Set thepushLevel.-
Methods declared in class java.util.logging.Handler
getEncoding, getErrorManager, getFilter, getFormatter, getLevel, reportError, setEncoding, setErrorManager, setFilter, setFormatter, setLevel
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Constructor Detail
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MemoryHandler
public MemoryHandler()
Create aMemoryHandlerand configure it based onLogManagerconfiguration properties.
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MemoryHandler
public MemoryHandler(Handler target, int size, Level pushLevel)
Create aMemoryHandler.The
MemoryHandleris configured based onLogManagerproperties (or their default values) except that the givenpushLevelargument 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
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Method Detail
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publish
public void publish(LogRecord record)
Store aLogRecordin an internal buffer.If there is a
Filter, itsisLoggablemethod 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 thepushLevel. If the given level is greater than or equal to thepushLevelthenpushis called to write all buffered records to the target outputHandler.
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push
public void push()
Push any buffered output to the targetHandler.The buffer is then cleared.
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flush
public void flush()
Causes a flush on the targetHandler.Note that the current contents of the
MemoryHandlerbuffer are not written out. That requires a "push".
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close
public void close() throws SecurityExceptionClose theHandlerand free all associated resources. This will also close the targetHandler.- Specified by:
closein classHandler- Throws:
SecurityException- if a security manager exists and if the caller does not haveLoggingPermission("control").
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setPushLevel
public void setPushLevel(Level newLevel) throws SecurityException
Set thepushLevel. After aLogRecordis copied into our internal buffer, if its level is greater than or equal to thepushLevel, thenpushwill be called.- Parameters:
newLevel- the new value of thepushLevel- Throws:
SecurityException- if a security manager exists and if the caller does not haveLoggingPermission("control").
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getPushLevel
public Level getPushLevel()
Get thepushLevel.- Returns:
- the value of the
pushLevel
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isLoggable
public boolean isLoggable(LogRecord record)
Check if thisHandlerwould actually log a givenLogRecordinto its internal buffer.This method checks if the
LogRecordhas an appropriate level and whether it satisfies anyFilter. However it does not check whether theLogRecordwould result in a "push" of the buffer contents. It will return false if theLogRecordis null.- Overrides:
isLoggablein classHandler- Parameters:
record- aLogRecord(may be null).- Returns:
- true if the
LogRecordwould be logged.
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