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:
LogRecord
has a type that is greater than a pre-defined level, the pushLevel
. push
method explicitly. 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
(defaults to Level.ALL
). Filter
class to use (defaults to no Filter
). pushLevel
(defaults to level.SEVERE
). Handler
class. (no default). For example, the properties for MemoryHandler
would be:
For a custom handler, e.g. com.foo.MyHandler, the properties would be:
Constructor | Description |
---|---|
MemoryHandler() |
Create a MemoryHandler and configure it based on LogManager configuration properties. |
MemoryHandler |
Create a MemoryHandler . |
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 |
Check if this Handler would actually log a given LogRecord into its internal buffer. |
void |
publish |
Store a LogRecord in an internal buffer. |
void |
push() |
Push any buffered output to the target Handler . |
void |
setPushLevel |
Set the pushLevel . |
getEncoding, getErrorManager, getFilter, getFormatter, getLevel, reportError, setEncoding, setErrorManager, setFilter, setFormatter, setLevel
public MemoryHandler()
MemoryHandler
and configure it based on LogManager
configuration properties.public MemoryHandler(Handler target, int size, Level pushLevel)
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.
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 onIllegalArgumentException
- if size is <= 0
public void publish(LogRecord record)
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
.
public void push()
Handler
. The buffer is then cleared.
public void flush()
Handler
. Note that the current contents of the MemoryHandler
buffer are not written out. That requires a "push".
public void close() throws SecurityException
Handler
and free all associated resources. This will also close the target Handler
.close
in class Handler
SecurityException
- if a security manager exists and if the caller does not have LoggingPermission("control")
.public void setPushLevel(Level newLevel) throws SecurityException
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.newLevel
- the new value of the pushLevel
SecurityException
- if a security manager exists and if the caller does not have LoggingPermission("control")
.public Level getPushLevel()
pushLevel
.pushLevel
public boolean isLoggable(LogRecord record)
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.
isLoggable
in class Handler
record
- a LogRecord
(may be null).LogRecord
would be logged.
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Licensed under the GNU General Public License, version 2, with the Classpath Exception.
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https://docs.oracle.com/en/java/javase/21/docs/api/java.logging/java/util/logging/MemoryHandler.html