# 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

Constructors
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 Handler

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

### Methods declared in class 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)
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.

### setEncoding

public void setEncoding(String encoding) throws 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:
  `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`
Implementation Requirements:
  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` - 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()
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`