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Class StreamHandler

java.lang.Object

java.util.logging.Handler

java.util.logging.StreamHandler

Direct Known Subclasses:: ConsoleHandler, FileHandler, SocketHandler

public class StreamHandler extends Handler

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

Since:: 1.4

Constructor Summary

Constructor	Description
`StreamHandler()`	Create a `StreamHandler`, with no current output stream.
`StreamHandler(OutputStream out, Formatter formatter)`	Create a `StreamHandler` with a given `Formatter` and output stream.

Method Summary

Modifier and Type	Method	Description
`void`	`close()`	Close the current output stream.
`void`	`flush()`	Flush any buffered messages.
`boolean`	`isLoggable(LogRecord record)`	Check if this `Handler` would actually log a given `LogRecord`.
`void`	`publish(LogRecord record)`	Format and publish a `LogRecord`.
`void`	`setEncoding(String encoding)`	Set (or change) the character encoding used by this `Handler`.
`protected void`	`setOutputStream(OutputStream out)`	Change the output stream.

Methods declared in class java.util.logging.Handler

getEncoding, getErrorManager, getFilter, getFormatter, getLevel, reportError, setErrorManager, setFilter, setFormatter, setLevel

Methods declared in class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

StreamHandler

public StreamHandler()

Create a StreamHandler, with no current output stream.

StreamHandler

public StreamHandler(OutputStream out, Formatter formatter)

Create a StreamHandler with a given Formatter and output stream.

Parameters:: out - the target output stream; formatter - Formatter to be used to format output

Method Details

setOutputStream

protected void setOutputStream(OutputStream out) throws SecurityException

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 - New output stream. May not be null.
Throws:: SecurityException - if a security manager exists and if the caller does not have LoggingPermission("control").

setEncoding

public void setEncoding(String encoding) throws SecurityException, UnsupportedEncodingException

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

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

Overrides:: setEncoding in class Handler
Parameters:: encoding - The name of a supported character encoding. May be null, to indicate the default platform encoding.
Throws:: SecurityException - if a security manager exists and if the caller does not have LoggingPermission("control").; UnsupportedEncodingException - if the named encoding is not supported.

publish

public void publish(LogRecord record)

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.

Specified by:: publish in class Handler
Parameters:: record - description of the log event. A null record is silently ignored and is not published

isLoggable

public boolean isLoggable(LogRecord record)

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.

Overrides:: isLoggable in class Handler
Parameters:: record - a LogRecord (may be null).
Returns:: true if the LogRecord would be logged.

flush

public void flush()

Flush any buffered messages.

Specified by:: flush in class Handler

close

public void close() throws SecurityException

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.

Specified by:: close in class Handler
Throws:: SecurityException - if a security manager exists and if the caller does not have LoggingPermission("control").

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Documentation extracted from Debian's OpenJDK Development Kit package.
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/StreamHandler.html