MemoryHandler (Java Platform SE 8 ) (original) (raw)

• 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 incomingLogRecord and calls push if a record matches some desired criteria.
  Configuration: By default each MemoryHandler is initialized using the followingLogManager configuration properties where 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.

• .level specifies the level for the Handler (defaults to Level.ALL).

• .filter specifies the name of a Filter class to use (defaults to no Filter).

• .size defines the buffer size (defaults to 1000).

• .push defines the pushLevel (defaults to level.SEVERE).

• .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 onLogManager configuration properties.
  MemoryHandler(Handler target, int size,Level pushLevel)	Create a MemoryHandler.

  • Method Summary

  All Methods Instance Methods Concrete Methods

  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 givenLogRecord 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](../../../java/util/logging/Handler.html "class in java.util.logging")  
     `[getEncoding](../../../java/util/logging/Handler.html#getEncoding--), [getErrorManager](../../../java/util/logging/Handler.html#getErrorManager--), [getFilter](../../../java/util/logging/Handler.html#getFilter--), [getFormatter](../../../java/util/logging/Handler.html#getFormatter--), [getLevel](../../../java/util/logging/Handler.html#getLevel--), [reportError](../../../java/util/logging/Handler.html#reportError-java.lang.String-java.lang.Exception-int-), [setEncoding](../../../java/util/logging/Handler.html#setEncoding-java.lang.String-), [setErrorManager](../../../java/util/logging/Handler.html#setErrorManager-java.util.logging.ErrorManager-), [setFilter](../../../java/util/logging/Handler.html#setFilter-java.util.logging.Filter-), [setFormatter](../../../java/util/logging/Handler.html#setFormatter-java.util.logging.Formatter-), [setLevel](../../../java/util/logging/Handler.html#setLevel-java.util.logging.Level-)`  
     * ### Methods inherited from class java.lang.[Object](../../../java/lang/Object.html "class in java.lang")  
     `[clone](../../../java/lang/Object.html#clone--), [equals](../../../java/lang/Object.html#equals-java.lang.Object-), [finalize](../../../java/lang/Object.html#finalize--), [getClass](../../../java/lang/Object.html#getClass--), [hashCode](../../../java/lang/Object.html#hashCode--), [notify](../../../java/lang/Object.html#notify--), [notifyAll](../../../java/lang/Object.html#notifyAll--), [toString](../../../java/lang/Object.html#toString--), [wait](../../../java/lang/Object.html#wait--), [wait](../../../java/lang/Object.html#wait-long-), [wait](../../../java/lang/Object.html#wait-long-int-)`

• • Constructor Detail

     * #### MemoryHandler  
     public MemoryHandler()  
     Create a  
     MemoryHandler  
      and configure it based on  
     LogManager  
      configuration properties.  
     * #### MemoryHandler  
     public MemoryHandler([Handler](../../../java/util/logging/Handler.html "class in java.util.logging") target,  
                          int size,  
                          [Level](../../../java/util/logging/Level.html "class in java.util.logging") 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](../../../java/lang/IllegalArgumentException.html "class in java.lang")` \- if `size is <= 0`  

  • Method Detail

    * #### publish  
    public void publish([LogRecord](../../../java/util/logging/LogRecord.html "class in java.util.logging") 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 outputHandler.  
    Specified by:  
    `[publish](../../../java/util/logging/Handler.html#publish-java.util.logging.LogRecord-)` in class `[Handler](../../../java/util/logging/Handler.html "class in java.util.logging")`  
    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](../../../java/util/logging/Handler.html#flush--)` in class `[Handler](../../../java/util/logging/Handler.html "class in java.util.logging")`  
    * #### close  
    public void close()  
               throws [SecurityException](../../../java/lang/SecurityException.html "class in java.lang")  
    Close the  
    Handler  
     and free all associated resources. This will also close the target  
    Handler  
    .  
    Specified by:  
    `[close](../../../java/util/logging/Handler.html#close--)` in class `[Handler](../../../java/util/logging/Handler.html "class in java.util.logging")`  
    Throws:  
    `[SecurityException](../../../java/lang/SecurityException.html "class in java.lang")` \- if a security manager exists and if the caller does not have LoggingPermission("control").  
    * #### setPushLevel  
    public void setPushLevel([Level](../../../java/util/logging/Level.html "class in java.util.logging") newLevel)  
                      throws [SecurityException](../../../java/lang/SecurityException.html "class in java.lang")  
    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](../../../java/lang/SecurityException.html "class in java.lang")` \- if a security manager exists and if the caller does not have LoggingPermission("control").  
    * #### getPushLevel  
    public [Level](../../../java/util/logging/Level.html "class in java.util.logging") getPushLevel()  
    Returns:  
    the value of the pushLevel  
    * #### isLoggable  
    public boolean isLoggable([LogRecord](../../../java/util/logging/LogRecord.html "class in java.util.logging") 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](../../../java/util/logging/Handler.html#isLoggable-java.util.logging.LogRecord-)` in class `[Handler](../../../java/util/logging/Handler.html "class in java.util.logging")`  
    Parameters:  
    `record` \- a LogRecord  
    Returns:  
    true if the LogRecord would be logged.

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