org.apache.commons.io.output

Class 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): 

     OutputStream out = ...
 Charset cs = ...
 OutputStreamWriter writer = new OutputStreamWriter(out, cs);
 WriterOutputStream out2 = new WriterOutputStream(writer, cs);
    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:
    ReaderInputStream

    • Constructor Detail

      • WriterOutputStream

        public WriterOutputStream(Writer writer,
                          CharsetDecoder decoder)
        Constructs a new WriterOutputStream with a default output buffer size of characters. The output buffer will only be flushed when it overflows or when flush() or close() is called.
        Parameters:
        writer - the target Writer
        decoder - the charset decoder
        Since:
        2.1

      • WriterOutputStream

        public WriterOutputStream(Writer writer,
                          CharsetDecoder decoder,
                          int bufferSize,
                          boolean writeImmediately)
        Constructs a new WriterOutputStream.
        Parameters:
        writer - the target Writer
        decoder - the charset decoder
        bufferSize - the size of the output buffer in number of characters
        writeImmediately - If true the output buffer will be flushed after each write operation, i.e. all available data will be written to the underlying Writer immediately. If false, the output buffer will only be flushed when it overflows or when flush() or close() is called.
        Since:
        2.1

      • WriterOutputStream

        public WriterOutputStream(Writer writer,
                          Charset charset,
                          int bufferSize,
                          boolean writeImmediately)
        Constructs a new WriterOutputStream.
        Parameters:
        writer - the target Writer
        charset - the charset encoding
        bufferSize - the size of the output buffer in number of characters
        writeImmediately - If true the output buffer will be flushed after each write operation, i.e. all available data will be written to the underlying Writer immediately. If false, the output buffer will only be flushed when it overflows or when flush() or close() is called.

      • WriterOutputStream

        public WriterOutputStream(Writer writer,
                          Charset charset)
        Constructs a new WriterOutputStream with a default output buffer size of characters. The output buffer will only be flushed when it overflows or when flush() or close() is called.
        Parameters:
        writer - the target Writer
        charset - the charset encoding

      • WriterOutputStream

        public WriterOutputStream(Writer writer,
                          String charsetName,
                          int bufferSize,
                          boolean writeImmediately)
        Constructs a new WriterOutputStream.
        Parameters:
        writer - the target Writer
        charsetName - the name of the charset encoding
        bufferSize - the size of the output buffer in number of characters
        writeImmediately - If true the output buffer will be flushed after each write operation, i.e. all available data will be written to the underlying Writer immediately. If false, the output buffer will only be flushed when it overflows or when flush() or close() is called.

      • WriterOutputStream

        public WriterOutputStream(Writer writer,
                          String charsetName)
        Constructs a new WriterOutputStream with a default output buffer size of characters. The output buffer will only be flushed when it overflows or when flush() or close() is called.
        Parameters:
        writer - the target Writer
        charsetName - the name of the charset encoding

    • Method Detail

      • write

        public void write(byte[] b,
                  int off,
                  int len)
           throws IOException
        Write bytes from the specified byte array to the stream.
        Overrides:
        write in class  OutputStream
        Parameters:
        b - the byte array containing the bytes to write
        off - the start offset in the byte array
        len - the number of bytes to write
        Throws:
        IOException - if an I/O error occurs.

      • write

        public void write(byte[] b)
           throws IOException
        Write bytes from the specified byte array to the stream.
        Overrides:
        write in class  OutputStream
        Parameters:
        b - the byte array containing the bytes to write
        Throws:
        IOException - if an I/O error occurs.

      • write

        public void write(int b)
           throws IOException
        Write a single byte to the stream.
        Specified by:
        write in class  OutputStream
        Parameters:
        b - the byte to write
        Throws:
        IOException - if an I/O error occurs.

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Group Id commons-io
Artifact Id commons-io
Version 2.11.0
Last Release 2.11.0
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Last Updated 2021-07-10