Package org.apache.commons.io.input

Class ReaderInputStream

java.lang.Object
java.io.InputStream
org.apache.commons.io.input.AbstractInputStream
org.apache.commons.io.input.ReaderInputStream
All Implemented Interfaces:
Closeable, AutoCloseable
public class ReaderInputStream extends AbstractInputStream
InputStream implementation that reads a character stream from a Reader and transforms it to a byte stream using a specified charset encoding. The stream is transformed using a CharsetEncoder object, guaranteeing that all charset encodings supported by the JRE are handled correctly. In particular for charsets such as UTF-16, the implementation ensures that one and only one byte order marker is produced.

Since in general it is not possible to predict the number of characters to be read from the Reader to satisfy a read request on the ReaderInputStream, all reads from the Reader are buffered. There is therefore no well defined correlation between the current position of the Reader and that of the ReaderInputStream. This also implies that in general there is no need to wrap the underlying Reader in a BufferedReader.

ReaderInputStream implements the inverse transformation of InputStreamReader; in the following example, reading from in2 would return the same byte sequence as reading from in (provided that the initial byte sequence is legal with respect to the charset encoding):

To build an instance, use ReaderInputStream.Builder. 

 InputStream inputStream = ...
 Charset cs = ...
 InputStreamReader reader = new InputStreamReader(inputStream, cs);
 ReaderInputStream in2 = ReaderInputStream.builder()
   .setReader(reader)
   .setCharset(cs)
   .get();

ReaderInputStream implements the same transformation as OutputStreamWriter, except that the control flow is reversed: both classes transform a character stream into a byte stream, but OutputStreamWriter pushes data to the underlying stream, while ReaderInputStream pulls it from 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 InputStream, but where the most natural way to produce the data is as a character stream, by providing a Reader instance. An example of a situation where this problem may appear is when implementing the javax.activation.DataSource interface from the Java Activation Framework.

The available() method of this class always returns 0. The methods InputStream.mark(int) and InputStream.reset() are not supported.

Instances of ReaderInputStream are not thread safe.

Since:
2.0
See Also:

  • Field Details

    • reader

      private final Reader reader

    • charsetEncoder

      private final CharsetEncoder charsetEncoder

    • encoderIn

      private final CharBuffer encoderIn
      CharBuffer used as input for the decoder. It should be reasonably large as we read data from the underlying Reader into this buffer.

    • encoderOut

      private final ByteBuffer encoderOut
      ByteBuffer used as output for the decoder. This buffer can be small as it is only used to transfer data from the decoder to the buffer provided by the caller.

    • lastCoderResult

      private CoderResult lastCoderResult

    • endOfInput

      private boolean endOfInput

  • Constructor Details

    • ReaderInputStream

      private ReaderInputStream(ReaderInputStream.Builder builder) throws IOException
      Throws:
      IOException

    • ReaderInputStream

      @Deprecated public ReaderInputStream(Reader reader)
      Deprecated.
      Use builder() instead.
      Constructs a new ReaderInputStream that uses the virtual machine's default charset with a default input buffer size of 8192 characters.
      Parameters:
      reader - the target Reader

    • ReaderInputStream

      @Deprecated public ReaderInputStream(Reader reader, Charset charset)
      Deprecated.
      Use builder() instead, will be protected for subclasses.
      Constructs a new ReaderInputStream with a default input buffer size of 8192 characters.

      The encoder created for the specified charset will use CodingErrorAction.REPLACE for malformed input and unmappable characters.

      Parameters:
      reader - the target Reader
      charset - the charset encoding.

    • ReaderInputStream

      @Deprecated public ReaderInputStream(Reader reader, Charset charset, int bufferSize)
      Deprecated.
      Use builder() instead.
      Constructs a new ReaderInputStream.

      The encoder created for the specified charset will use CodingErrorAction.REPLACE for malformed input and unmappable characters.

      Parameters:
      reader - the target Reader.
      charset - the charset encoding.
      bufferSize - the size of the input buffer in number of characters.

    • ReaderInputStream

      @Deprecated public ReaderInputStream(Reader reader, CharsetEncoder charsetEncoder)
      Deprecated.
      Use builder() instead.
      Constructs a new ReaderInputStream.

      This constructor does not call reset on the provided encoder. The caller of this constructor should do this when providing an encoder which had already been in use.

      Parameters:
      reader - the target Reader
      charsetEncoder - the charset encoder.
      Since:
      2.1

    • ReaderInputStream

      @Deprecated public ReaderInputStream(Reader reader, CharsetEncoder charsetEncoder, int bufferSize)
      Deprecated.
      Use builder() instead.
      Constructs a new ReaderInputStream.

      This constructor does not call reset on the provided encoder. The caller of this constructor should do this when providing an encoder which had already been in use.

      Parameters:
      reader - the target Reader
      charsetEncoder - the charset encoder, null defaults to the default Charset encoder.
      bufferSize - the size of the input buffer in number of characters.
      Since:
      2.1

    • ReaderInputStream

      @Deprecated public ReaderInputStream(Reader reader, String charsetName)
      Deprecated.
      Use builder() instead.
      Constructs a new ReaderInputStream with a default input buffer size of 8192 characters.

      The encoder created for the specified charset will use CodingErrorAction.REPLACE for malformed input and unmappable characters.

      Parameters:
      reader - the target Reader
      charsetName - the name of the charset encoding.

    • ReaderInputStream

      @Deprecated public ReaderInputStream(Reader reader, String charsetName, int bufferSize)
      Deprecated.
      Use builder() instead.
      Constructs a new ReaderInputStream.

      The encoder created for the specified charset will use CodingErrorAction.REPLACE for malformed input and unmappable characters.

      Parameters:
      reader - the target Reader
      charsetName - the name of the charset encoding, null maps to the default Charset.
      bufferSize - the size of the input buffer in number of characters.

  • Method Details