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.
ReaderInputStream.Builder,
WriterOutputStream| Modifier and Type | Class and Description |
|---|---|
static class |
ReaderInputStream.Builder
Constructs a new
ReaderInputStream with a default input buffer size of IOUtils.DEFAULT_BUFFER_SIZE characters. |
| Modifier and Type | Method and Description |
|---|---|
int |
available() |
static ReaderInputStream.Builder |
builder()
Constructs a new
ReaderInputStream.Builder. |
(package private) static int |
checkMinBufferSize(CharsetEncoder charsetEncoder,
int bufferSize) |
void |
close()
Closes the stream.
|
(package private) CharsetEncoder |
getCharsetEncoder()
Gets the CharsetEncoder.
|
(package private) static float |
minBufferSize(CharsetEncoder charsetEncoder) |
int |
read()
Reads a single byte.
|
int |
read(byte[] b)
Reads the specified number of bytes into an array.
|
int |
read(byte[] array,
int off,
int len)
Reads the specified number of bytes into an array.
|
checkOpen, isClosed, setClosedmark, markSupported, reset, skippublic int available()
throws IOException
available in class InputStreamIOExceptionpublic static ReaderInputStream.Builder builder()
ReaderInputStream.Builder.ReaderInputStream.Builder.static int checkMinBufferSize(CharsetEncoder charsetEncoder, int bufferSize)
public void close()
throws IOException
Reader to be closed.close in interface Closeableclose in interface AutoCloseableclose in class AbstractInputStreamIOException - if an I/O error occurs.CharsetEncoder getCharsetEncoder()
static float minBufferSize(CharsetEncoder charsetEncoder)
public int read()
throws IOException
read in class InputStream-1 if the end of the stream has been reachedIOException - if an I/O error occurs.public 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 occurs.public int read(byte[] array,
int off,
int len)
throws IOException
read in class InputStreamarray - 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 occurs.