Package org.apache.commons.io.output

Class WriterOutputStream

  • All Implemented Interfaces:
    java.io.Closeable, java.io.Flushable, java.lang.AutoCloseable
    public class WriterOutputStream
extends java.io.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

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      void close()
      Close the stream.
      void flush()
      Flush the stream.
      void write​(byte[] b)
      Write bytes from the specified byte array to the stream.
      void write​(byte[] b, int off, int len)
      Write bytes from the specified byte array to the stream.
      void write​(int b)
      Write a single byte to the stream.

      • Methods inherited from class java.io.OutputStream

        nullOutputStream

      • Methods inherited from class java.lang.Object

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

    • Constructor Detail

      • WriterOutputStream

        public WriterOutputStream​(java.io.Writer writer,
                          java.nio.charset.CharsetDecoder decoder)
        Constructs a new WriterOutputStream with a default output buffer size of 1024 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​(java.io.Writer writer,
                          java.nio.charset.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​(java.io.Writer writer,
                          java.nio.charset.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​(java.io.Writer writer,
                          java.nio.charset.Charset charset)
        Constructs a new WriterOutputStream with a default output buffer size of 1024 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​(java.io.Writer writer,
                          java.lang.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​(java.io.Writer writer,
                          java.lang.String charsetName)
        Constructs a new WriterOutputStream with a default output buffer size of 1024 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

      • WriterOutputStream

        @Deprecated
public WriterOutputStream​(java.io.Writer writer)
        Deprecated.
        2.5 use WriterOutputStream(Writer, Charset) instead
        Constructs a new WriterOutputStream that uses the default character encoding and with a default output buffer size of 1024 characters. The output buffer will only be flushed when it overflows or when flush() or close() is called.
        Parameters:
        writer - the target Writer

    • Method Detail

      • write

        public void write​(byte[] b,
                  int off,
                  int len)
           throws java.io.IOException
        Write bytes from the specified byte array to the stream.
        Overrides:
        write in class java.io.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:
        java.io.IOException - if an I/O error occurs.

      • write

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

      • write

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

      • flush

        public void flush()
           throws java.io.IOException
        Flush the stream. Any remaining content accumulated in the output buffer will be written to the underlying Writer. After that Writer.flush() will be called.
        Specified by:
        flush in interface java.io.Flushable
        Overrides:
        flush in class java.io.OutputStream
        Throws:
        java.io.IOException - if an I/O error occurs.

      • close

        public void close()
           throws java.io.IOException
        Close the stream. Any remaining content accumulated in the output buffer will be written to the underlying Writer. After that Writer.close() will be called.
        Specified by:
        close in interface java.lang.AutoCloseable
        Specified by:
        close in interface java.io.Closeable
        Overrides:
        close in class java.io.OutputStream
        Throws:
        java.io.IOException - if an I/O error occurs.