public class ReaderInputStream extends InputStream
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):
InputStream in = ... Charset cs = ... InputStreamReader reader = new InputStreamReader(in, cs); ReaderInputStream in2 = new ReaderInputStream(reader, cs);
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, i.e. by providing a
Reader instance. An example of a situation where this problem may appear is when
implementing the DataSource interface from the Java Activation
Framework.
Given the fact that the Reader class doesn't provide any way to predict whether the next
read operation will block or not, it is not possible to provide a meaningful implementation of
the InputStream.available() method. A call to this method will always return 0. Also,
this class doesn't support InputStream.mark(int).
Instances of ReaderInputStream are not thread safe.
| Constructor and Description |
|---|
ReaderInputStream(Reader reader,
Charset charset)
Construct a new
ReaderInputStream with a default input buffer size of
1024 characters. |
| Modifier and Type | Method and Description |
|---|---|
void |
close()
Close the stream.
|
int |
read()
Read a single byte.
|
int |
read(byte[] b)
Read the specified number of bytes into an array.
|
int |
read(byte[] b,
int off,
int len)
Read the specified number of bytes into an array.
|
available, mark, markSupported, reset, skippublic ReaderInputStream(Reader reader, Charset charset)
ReaderInputStream with a default input buffer size of
1024 characters.reader - the target Readercharset - the charset encodingpublic int read(byte[] b,
int off,
int len)
throws IOException
read in class InputStreamb - the byte array to read intooff - the offset to start reading bytes intolen - the number of bytes to read-1 if the end of the stream has been reachedIOException - if an I/O error occurspublic int read(byte[] b)
throws IOException
read in class InputStreamb - the byte array to read into-1 if the end of the stream has been reachedIOException - if an I/O error occurspublic int read()
throws IOException
read in class InputStream-1 if the end of the stream
has been reachedIOException - if an I/O error occurspublic void close()
throws IOException
Reader to be closed.close in interface Closeableclose in interface AutoCloseableclose in class InputStreamIOException - if an I/O error occursCopyright © 2015. All rights reserved.