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:

  • Constructor Details

    • ReaderInputStream

      @Deprecated public ReaderInputStream(Reader reader)
      Deprecated.
      Use builder() instead
      Constructs a new ReaderInputStream that uses the default character encoding 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

    • builder

      public static ReaderInputStream.Builder builder()
      Constructs a new ReaderInputStream.Builder.
      Returns:
      a new ReaderInputStream.Builder.
      Since:
      2.12.0

    • available

      public int available() throws IOException
      Overrides:
      available in class InputStream
      Throws:
      IOException

    • close

      public void close() throws IOException
      Closes the stream. This method will cause the underlying Reader to be closed.
      Specified by:
      close in interface AutoCloseable
      Specified by:
      close in interface Closeable
      Overrides:
      close in class AbstractInputStream
      Throws:
      IOException - if an I/O error occurs.

    • read

      public int read() throws IOException
      Reads a single byte.
      Specified by:
      read in class InputStream
      Returns:
      either the byte read or -1 if the end of the stream has been reached
      Throws:
      IOException - if an I/O error occurs.

    • read

      public int read(byte[] b) throws IOException
      Reads the specified number of bytes into an array.
      Overrides:
      read in class InputStream
      Parameters:
      b - the byte array to read into
      Returns:
      the number of bytes read or -1 if the end of the stream has been reached
      Throws:
      IOException - if an I/O error occurs.

    • read

      public int read(byte[] array, int off, int len) throws IOException
      Reads the specified number of bytes into an array.
      Overrides:
      read in class InputStream
      Parameters:
      array - the byte array to read into
      off - the offset to start reading bytes into
      len - the number of bytes to read
      Returns:
      the number of bytes read or -1 if the end of the stream has been reached
      Throws:
      IOException - if an I/O error occurs.