public class ReaderInputStream
extends java.io.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.
WriterOutputStream| Constructor and Description |
|---|
ReaderInputStream(java.io.Reader reader)
Construct a new
ReaderInputStream that uses the default character encoding
with a default input buffer size of 1024 characters. |
ReaderInputStream(java.io.Reader reader,
java.nio.charset.Charset charset)
Construct a new
ReaderInputStream with a default input buffer size of
1024 characters. |
ReaderInputStream(java.io.Reader reader,
java.nio.charset.CharsetEncoder encoder)
Construct a new
ReaderInputStream. |
ReaderInputStream(java.io.Reader reader,
java.nio.charset.CharsetEncoder encoder,
int bufferSize)
Construct a new
ReaderInputStream. |
ReaderInputStream(java.io.Reader reader,
java.nio.charset.Charset charset,
int bufferSize)
Construct a new
ReaderInputStream. |
ReaderInputStream(java.io.Reader reader,
java.lang.String charsetName)
Construct a new
ReaderInputStream with a default input buffer size of
1024 characters. |
ReaderInputStream(java.io.Reader reader,
java.lang.String charsetName,
int bufferSize)
Construct a new
ReaderInputStream. |
| 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.
|
public ReaderInputStream(java.io.Reader reader,
java.nio.charset.CharsetEncoder encoder)
ReaderInputStream.reader - the target Readerencoder - the charset encoderpublic ReaderInputStream(java.io.Reader reader,
java.nio.charset.CharsetEncoder encoder,
int bufferSize)
ReaderInputStream.reader - the target Readerencoder - the charset encoderbufferSize - the size of the input buffer in number of characterspublic ReaderInputStream(java.io.Reader reader,
java.nio.charset.Charset charset,
int bufferSize)
ReaderInputStream.reader - the target Readercharset - the charset encodingbufferSize - the size of the input buffer in number of characterspublic ReaderInputStream(java.io.Reader reader,
java.nio.charset.Charset charset)
ReaderInputStream with a default input buffer size of
1024 characters.reader - the target Readercharset - the charset encodingpublic ReaderInputStream(java.io.Reader reader,
java.lang.String charsetName,
int bufferSize)
ReaderInputStream.reader - the target ReadercharsetName - the name of the charset encodingbufferSize - the size of the input buffer in number of characterspublic ReaderInputStream(java.io.Reader reader,
java.lang.String charsetName)
ReaderInputStream with a default input buffer size of
1024 characters.reader - the target ReadercharsetName - the name of the charset encodingpublic ReaderInputStream(java.io.Reader reader)
ReaderInputStream that uses the default character encoding
with a default input buffer size of 1024 characters.reader - the target Readerpublic int read(byte[] b,
int off,
int len)
throws java.io.IOException
read in class java.io.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 reachedjava.io.IOException - if an I/O error occurspublic int read(byte[] b)
throws java.io.IOException
read in class java.io.InputStreamb - the byte array to read into-1
if the end of the stream has been reachedjava.io.IOException - if an I/O error occurspublic int read()
throws java.io.IOException
read in class java.io.InputStream-1 if the end of the stream
has been reachedjava.io.IOException - if an I/O error occurspublic void close()
throws java.io.IOException
Reader
to be closed.close in interface java.io.Closeableclose in interface java.lang.AutoCloseableclose in class java.io.InputStreamjava.io.IOException - if an I/O error occurs