OpenJDK 27 · java.util.logging.StreamHandler · APIdia, the JavaDoc alternative

Stream based logging Handler.

This is primarily intended as a base class or support class to be used in implementing other logging Handlers.

LogRecords are published to a given java.io.OutputStream.

Configuration: By default each StreamHandler 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.

<handler-name>.level specifies the default level for the Handler (defaults to Level.INFO).
<handler-name>.filter specifies the name of a Filter class to use (defaults to no Filter).
<handler-name>.formatter specifies the name of a Formatter class to use (defaults to java.util.logging.SimpleFormatter).
<handler-name>.encoding the name of the character set encoding to use (defaults to the default platform encoding).

For example, the properties for StreamHandler would be:

java.util.logging.StreamHandler.level=INFO
java.util.logging.StreamHandler.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

Field Summary

Modifier and Type	Field and Description
private boolean	doneHeader
private OutputStream	output
private volatile Writer	writer

Constructor Summary

Access	Constructor and Description
public	StreamHandler() Create a `StreamHandler`, with no current output stream.
public	StreamHandler(OutputStream the target output stream out, Formatter Formatter to be used to format output formatter) Create a `StreamHandler` with a given `Formatter` and output stream.
pack-priv	StreamHandler(Level defaultLevel, Formatter defaultFormatter, Formatter specifiedFormatter)

Method Summary

Modifier and Type	Method and Description
public synchronized void	close() Implements abstract java.util.logging.Handler.close. Close the current output stream.
public synchronized void	flush() Implements abstract java.util.logging.Handler.flush. Flush any buffered messages.
private void	flushAndClose()
public boolean	Returns: true if the `LogRecord` would be logged. isLoggable(LogRecord a `LogRecord` (may be null). record) Overrides java.util.logging.Handler.isLoggable. Check if this `Handler` would actually log a given `LogRecord`.
public void	publish(LogRecord description of the log event. A null record is silently ignored and is not published record) Implements abstract java.util.logging.Handler.publish. Format and publish a `LogRecord`.
public synchronized void	setEncoding(String The name of a supported character encoding. May be null, to indicate the default platform encoding. encoding) Overrides java.util.logging.Handler.setEncoding. Set (or change) the character encoding used by this `Handler`.
protected synchronized void	setOutputStream(OutputStream New output stream. May not be null. out) Change the output stream.
pack-priv void	synchronousPostWriteHook() Overridden by other handlers in this package to facilitate synchronous post-write behaviour.

Inherited from java.util.logging.Handler:: getEncoding getErrorManager getFilter getFormatter getLevel reportError setErrorManager setFilter setFormatter setLevel

Field Detail

doneHeader	back to summary
private boolean doneHeader

output	back to summary
private OutputStream output

writer	back to summary
private volatile Writer writer

Constructor Detail

StreamHandler	back to summary
public StreamHandler() Create a `StreamHandler`, with no current output stream.

StreamHandler back to summary

StreamHandler	back to summary
public StreamHandler(OutputStream out, Formatter formatter) Create a `StreamHandler` with a given `Formatter` and output stream. Parameters out:OutputStream the target output stream formatter:Formatter Formatter to be used to format output

public StreamHandler(OutputStream out, Formatter formatter)

Create a StreamHandler with a given Formatter and output stream.

Parameters

out:OutputStream: the target output stream
formatter:Formatter: Formatter to be used to format output

StreamHandler	back to summary
pack-priv StreamHandler(Level defaultLevel, Formatter defaultFormatter, Formatter specifiedFormatter) See Also `Handler#Handler(Level, Formatter, Formatter)`

Method Detail

close back to summary

close	back to summary
public synchronized void close() Implements abstract java.util.logging.Handler.close. Close the current output stream. The `Formatter`'s "tail" string is written to the stream before it is closed. In addition, if the `Formatter`'s "head" string has not yet been written to the stream, it will be written before the "tail" string. Annotations @Override

public synchronized void close()

Implements abstract java.util.logging.Handler.close.

Close the current output stream.

The Formatter's "tail" string is written to the stream before it is closed. In addition, if the Formatter's "head" string has not yet been written to the stream, it will be written before the "tail" string.

Annotations

@Override

flush	back to summary
public synchronized void flush() Implements abstract java.util.logging.Handler.flush. Flush any buffered messages. Annotations @Override

flush

back to summary

public synchronized void flush()

Implements abstract java.util.logging.Handler.flush.

Flush any buffered messages.

Annotations

@Override

flushAndClose	back to summary
private void flushAndClose()

isLoggable back to summary

isLoggable	back to summary
public boolean isLoggable(LogRecord record) Overrides java.util.logging.Handler.isLoggable. Check if this `Handler` would actually log a given `LogRecord`. This method checks if the `LogRecord` has an appropriate level and whether it satisfies any `Filter`. It will also return false if no output stream has been assigned yet or the LogRecord is null. Parameters record:LogRecord a `LogRecord` (may be null). Returns:boolean true if the `LogRecord` would be logged. Annotations @Override

public boolean isLoggable(LogRecord record)

Overrides java.util.logging.Handler.isLoggable.

Check if this Handler would actually log a given LogRecord.

This method checks if the LogRecord has an appropriate level and whether it satisfies any Filter. It will also return false if no output stream has been assigned yet or the LogRecord is null.

Parameters

record:LogRecord: a LogRecord (may be null).

Returns:boolean

true if the LogRecord would be logged.

Annotations

@Override

publish back to summary

publish	back to summary
public void publish(LogRecord record) Implements abstract java.util.logging.Handler.publish. Format and publish a `LogRecord`. The `StreamHandler` first checks if there is an `OutputStream` and if the given `LogRecord` has at least the required log level. If not it silently returns. If so, it calls any associated `Filter` to check if the record should be published. If so, it calls its `Formatter` to format the record and then writes the result to the current output stream. If this is the first `LogRecord` to be written to a given `OutputStream`, the `Formatter`'s "head" string is written to the stream before the `LogRecord` is written. Implementation Specification This method avoids acquiring locks during `LogRecord` formatting, but `this` instance is synchronized when writing to the output stream. To avoid deadlock risk, subclasses must not hold locks while calling `super.publish()`. Specifically, subclasses must not define the overridden `publish()` method to be `synchronized` if they call `super.publish()`. Parameters record:LogRecord description of the log event. A null record is silently ignored and is not published Annotations @Override

public void publish(LogRecord record)

Implements abstract java.util.logging.Handler.publish.

Format and publish a LogRecord.

The StreamHandler first checks if there is an OutputStream and if the given LogRecord has at least the required log level. If not it silently returns. If so, it calls any associated Filter to check if the record should be published. If so, it calls its Formatter to format the record and then writes the result to the current output stream.

If this is the first LogRecord to be written to a given OutputStream, the Formatter's "head" string is written to the stream before the LogRecord is written.

Implementation Specification

This method avoids acquiring locks during LogRecord formatting, but this instance is synchronized when writing to the output stream. To avoid deadlock risk, subclasses must not hold locks while calling super.publish(). Specifically, subclasses must not define the overridden publish() method to be synchronized if they call super.publish().

Parameters

record:LogRecord: description of the log event. A null record is silently ignored and is not published

Annotations

@Override

setEncoding back to summary

setEncoding	back to summary
public synchronized void setEncoding(String encoding) throws UnsupportedEncodingException Overrides java.util.logging.Handler.setEncoding. Set (or change) the character encoding used by this `Handler`. The encoding should be set before any `LogRecords` are written to the `Handler`. Parameters encoding:String The name of a supported character encoding. May be null, to indicate the default platform encoding. Annotations @Override Exceptions UnsupportedEncodingException: if the named encoding is not supported.

public synchronized void setEncoding(String encoding) throws UnsupportedEncodingException

Overrides java.util.logging.Handler.setEncoding.

Set (or change) the character encoding used by this Handler.

The encoding should be set before any LogRecords are written to the Handler.

Parameters

encoding:String: The name of a supported character encoding. May be null, to indicate the default platform encoding.

Annotations

@Override

Exceptions

UnsupportedEncodingException:: if the named encoding is not supported.

setOutputStream back to summary

setOutputStream	back to summary
protected synchronized void setOutputStream(OutputStream out) Change the output stream. If there is a current output stream then the `Formatter`'s tail string is written and the stream is flushed and closed. Then the output stream is replaced with the new output stream. Parameters out:OutputStream New output stream. May not be null.

protected synchronized void setOutputStream(OutputStream out)

Change the output stream.

If there is a current output stream then the Formatter's tail string is written and the stream is flushed and closed. Then the output stream is replaced with the new output stream.

Parameters

out:OutputStream: New output stream. May not be null.

synchronousPostWriteHook	back to summary
pack-priv void synchronousPostWriteHook() Overridden by other handlers in this package to facilitate synchronous post-write behaviour. If other handlers need similar functionality, it might be feasible to make this method protected (see JDK-8349206), but please find a better name if you do ;).

public Class StreamHandler

Field Summary

Constructor Summary

Method Summary

Field Detail

Constructor Detail

Method Detail