Package org.apache.commons.io.output

Class WriterOutputStream

java.lang.Object
java.io.OutputStream
org.apache.commons.io.output.WriterOutputStream
All Implemented Interfaces:
Closeable, Flushable, AutoCloseable
public class WriterOutputStream extends OutputStream
OutputStream implementation that transforms a byte stream to a character stream using a specified charset encoding and writes the resulting stream to a Writer. The stream is transformed using a CharsetDecoder object, guaranteeing that all charset encodings supported by the JRE are handled correctly.

The output of the CharsetDecoder is buffered using a fixed size buffer. This implies that the data is written to the underlying Writer in chunks that are no larger than the size of this buffer. By default, the buffer is flushed only when it overflows or when flush() or close() is called. In general there is therefore no need to wrap the underlying Writer in a BufferedWriter. WriterOutputStream can also be instructed to flush the buffer after each write operation. In this case, all available data is written immediately to the underlying Writer, implying that the current position of the Writer is correlated to the current position of the WriterOutputStream.

WriterOutputStream implements the inverse transformation of OutputStreamWriter; in the following example, writing to out2 would have the same result as writing to out directly (provided that the byte sequence is legal with respect to the charset encoding):

To build an instance, use WriterOutputStream.Builder. 

 OutputStream out = ...
 Charset cs = ...
 OutputStreamWriter writer = new OutputStreamWriter(out, cs);
 WriterOutputStream out2 = WriterOutputStream.builder()
   .setWriter(writer)
   .setCharset(cs)
   .get();

WriterOutputStream implements the same transformation as InputStreamReader, except that the control flow is reversed: both classes transform a byte stream into a character stream, but InputStreamReader pulls data from the underlying stream, while WriterOutputStream pushes it to the underlying stream.

Note that while there are use cases where there is no alternative to using this class, very often the need to use this class is an indication of a flaw in the design of the code. This class is typically used in situations where an existing API only accepts an OutputStream object, but where the stream is known to represent character data that must be decoded for further use.

Instances of WriterOutputStream are not thread safe.

Since:
2.0
See Also: