java.util.logging

Class Handler

public abstract class Handler extends Object

A Handler publishes LogRecords to a sink, for example a file, the console or a network socket. There are different subclasses of Handler to deal with different kinds of sinks.

FIXME: Are handlers thread-safe, or is the assumption that only loggers are, and a handler can belong only to one single logger? If the latter, should we enforce it? (Spec not clear). In any case, it needs documentation.

Constructor Summary
protected	Handler() Constructs a Handler with a logging severity level of `Level.ALL`, no formatter, no filter, and an instance of `ErrorManager` managing errors.

Method Summary
abstract void	close() Closes this `Handler` after having flushed the buffers.
abstract void	flush() Forces any data that may have been buffered to the underlying output device.
String	getEncoding() Returns the character encoding which this handler uses for publishing log records.
ErrorManager	getErrorManager() Returns the `ErrorManager` that currently deals with errors originating from this Handler.
Filter	getFilter() Returns the `Filter` that currently controls which log records are being published by this `Handler`.
Formatter	getFormatter() Returns the `Formatter` which will be used to localize the text of log messages and to substitute message parameters.
Level	getLevel() Returns the severity level threshold for this `Handler` All log records with a lower severity level will be discarded; a log record of the same or a higher level will be published unless an installed `Filter` decides to discard it.
boolean	isLoggable(LogRecord record) Checks whether a `LogRecord` would be logged if it was passed to this `Handler` for publication.
abstract void	publish(LogRecord record) Publishes a `LogRecord` to an appropriate sink, provided the record passes all tests for being loggable.
protected void	reportError(String message, Exception ex, int code)
void	setEncoding(String encoding) Sets the character encoding which this handler uses for publishing log records.
void	setErrorManager(ErrorManager manager)
void	setFilter(Filter filter) Sets the `Filter` for controlling which log records will be published by this `Handler`.
void	setFormatter(Formatter formatter) Sets the `Formatter` which will be used to localize the text of log messages and to substitute message parameters.
void	setLevel(Level level) Sets the severity level threshold for this `Handler`.

Constructor Detail

Handler

protected Handler()

Constructs a Handler with a logging severity level of Level.ALL, no formatter, no filter, and an instance of ErrorManager managing errors.

Specification Note: The specification of the Java^TM Logging API does not mention which character encoding is to be used by freshly constructed Handlers. The GNU implementation uses the default platform encoding, but other Java implementations might behave differently.

Specification Note: While a freshly constructed Handler is required to have no filter according to the specification, null is not a valid parameter for Handler.setFormatter. Therefore, the following code will throw a java.lang.NullPointerException:

Handler h = new MyConcreteSubclassOfHandler();
h.setFormatter(h.getFormatter());

It seems strange that a freshly constructed Handler is not supposed to provide a Formatter, but this is what the specification says.

Method Detail

close

public abstract void close()

Closes this Handler after having flushed the buffers. As soon as close has been called, a Handler should not be used anymore. Attempts to publish log records, to flush buffers, or to modify the Handler in any other way may throw runtime exceptions after calling close.

In case of an I/O failure, the ErrorManager of this Handler will be informed, but the caller of this method will not receive an exception.

Throws: SecurityException if a security manager exists and the caller is not granted the permission to control the logging infrastructure.

flush

public abstract void flush()

Forces any data that may have been buffered to the underlying output device.

In case of an I/O failure, the ErrorManager of this Handler will be informed, but the caller of this method will not receive an exception.

getEncoding

public String getEncoding()

Returns the character encoding which this handler uses for publishing log records.

Returns: the name of a character encoding, or null for the default platform encoding.

getErrorManager

public ErrorManager getErrorManager()

Returns the ErrorManager that currently deals with errors originating from this Handler.

Throws: SecurityException if a security manager exists and the caller is not granted the permission to control the logging infrastructure.

getFilter

public Filter getFilter()

Returns the Filter that currently controls which log records are being published by this Handler.

Returns: the currently active Filter, or null if no filter has been associated. In the latter case, log records are filtered purely based on their severity level.

getFormatter

public Formatter getFormatter()

Returns the Formatter which will be used to localize the text of log messages and to substitute message parameters. A Handler is encouraged, but not required to actually use an assigned Formatter.

Returns: the Formatter being used, or null if this Handler does not use formatters and no formatter has ever been set by calling setFormatter.

getLevel

public Level getLevel()

Returns the severity level threshold for this Handler All log records with a lower severity level will be discarded; a log record of the same or a higher level will be published unless an installed Filter decides to discard it.

Returns: the severity level below which all log messages will be discarded.

isLoggable

public boolean isLoggable(LogRecord record)

Checks whether a LogRecord would be logged if it was passed to this Handler for publication.

The Handler implementation considers a record as loggable if its level is greater than or equal to the severity level threshold. In a second step, if a {@link Filter} has been installed, its {@link Filter#isLoggable(LogRecord) isLoggable} method is invoked. Subclasses of Handler can override this method to impose their own constraints.

Parameters: record the LogRecord to be checked.

Returns: true if record would be published by {@link #publish(LogRecord) publish}, false if it would be discarded.

Throws: NullPointerException if record is null.

publish

public abstract void publish(LogRecord record)

Publishes a LogRecord to an appropriate sink, provided the record passes all tests for being loggable. The Handler will localize the message of the log record and substitute any message parameters.

Most applications do not need to call this method directly. Instead, they will use use a {@link Logger}, which will create LogRecords and distribute them to registered handlers.

In case of an I/O failure, the ErrorManager of this Handler will be informed, but the caller of this method will not receive an exception.

Parameters: record the log event to be published.

reportError

protected void reportError(String message, Exception ex, int code)

setEncoding

public void setEncoding(String encoding)

Sets the character encoding which this handler uses for publishing log records. The encoding of a Handler must be set before any log records have been published.

Parameters: encoding the name of a character encoding, or null for the default encoding.

Throws: SecurityException if a security manager exists and the caller is not granted the permission to control the logging infrastructure.

setErrorManager

public void setErrorManager(ErrorManager manager)

setFilter

public void setFilter(Filter filter)

Sets the Filter for controlling which log records will be published by this Handler.

Parameters: filter the Filter to use, or null to filter log records purely based on their severity level.

setFormatter

public void setFormatter(Formatter formatter)

Sets the Formatter which will be used to localize the text of log messages and to substitute message parameters. A Handler is encouraged, but not required to actually use an assigned Formatter.

Parameters: formatter the new Formatter to use.

Throws: SecurityException if a security manager exists and the caller is not granted the permission to control the logging infrastructure. NullPointerException if formatter is null.

setLevel

public void setLevel(Level level)

Sets the severity level threshold for this Handler. All log records with a lower severity level will be discarded; a log record of the same or a higher level will be published unless an installed Filter decides to discard it.

Parameters: level the severity level below which all log messages will be discarded.

Throws: SecurityException if a security manager exists and the caller is not granted the permission to control the logging infrastructure. NullPointerException if level is null.