com.networknt.utility.StreamUtils Maven / Gradle / Ivy
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package com.networknt.utility;
import java.io.*;
import java.nio.charset.Charset;
/**
* Simple utility methods for dealing with streams. The copy methods of this class are
* similar to those defined in FileCopyUtils except that all affected streams are
* left open when done. All copy methods use a block size of 4096 bytes.
*
* Mainly for use within the framework, but also useful for application code.
*
* @author Juergen Hoeller
* @author Phillip Webb
* @author Brian Clozel
* @since 3.2.2
*/
public abstract class StreamUtils {
/**
* The default buffer size used when copying bytes.
*/
public static final int BUFFER_SIZE = 4096;
private static final byte[] EMPTY_CONTENT = new byte[0];
/**
* Copy the contents of the given InputStream into a new byte array.
*
Leaves the stream open when done.
* @param in the stream to copy from (may be {@code null} or empty)
* @return the new byte array that has been copied to (possibly empty)
* @throws IOException in case of I/O errors
*/
public static byte[] copyToByteArray(InputStream in) throws IOException {
if (in == null) {
return new byte[0];
}
ByteArrayOutputStream out = new ByteArrayOutputStream(BUFFER_SIZE);
copy(in, out);
return out.toByteArray();
}
/**
* Copy the contents of the given InputStream into a String.
*
Leaves the stream open when done.
* @param in the InputStream to copy from (may be {@code null} or empty)
* @param charset the {@link Charset} to use to decode the bytes
* @return the String that has been copied to (possibly empty)
* @throws IOException in case of I/O errors
*/
public static String copyToString(InputStream in, Charset charset) throws IOException {
if (in == null) {
return "";
}
StringBuilder out = new StringBuilder(BUFFER_SIZE);
InputStreamReader reader = new InputStreamReader(in, charset);
char[] buffer = new char[BUFFER_SIZE];
int charsRead;
while ((charsRead = reader.read(buffer)) != -1) {
out.append(buffer, 0, charsRead);
}
return out.toString();
}
/**
* Copy the contents of the given {@link ByteArrayOutputStream} into a {@link String}.
*
This is a more effective equivalent of {@code new String(baos.toByteArray(), charset)}.
* @param baos the {@code ByteArrayOutputStream} to be copied into a String
* @param charset the {@link Charset} to use to decode the bytes
* @return the String that has been copied to (possibly empty)
* @since 5.2.6
*/
public static String copyToString(ByteArrayOutputStream baos, Charset charset) {
try {
// Can be replaced with toString(Charset) call in Java 10+
return baos.toString(charset.name());
}
catch (UnsupportedEncodingException ex) {
// Should never happen
throw new IllegalArgumentException("Invalid charset name: " + charset, ex);
}
}
/**
* Copy the contents of the given byte array to the given OutputStream.
*
Leaves the stream open when done.
* @param in the byte array to copy from
* @param out the OutputStream to copy to
* @throws IOException in case of I/O errors
*/
public static void copy(byte[] in, OutputStream out) throws IOException {
out.write(in);
out.flush();
}
/**
* Copy the contents of the given String to the given OutputStream.
*
Leaves the stream open when done.
* @param in the String to copy from
* @param charset the Charset
* @param out the OutputStream to copy to
* @throws IOException in case of I/O errors
*/
public static void copy(String in, Charset charset, OutputStream out) throws IOException {
Writer writer = new OutputStreamWriter(out, charset);
writer.write(in);
writer.flush();
}
/**
* Copy the contents of the given InputStream to the given OutputStream.
*
Leaves both streams open when done.
* @param in the InputStream to copy from
* @param out the OutputStream to copy to
* @return the number of bytes copied
* @throws IOException in case of I/O errors
*/
public static int copy(InputStream in, OutputStream out) throws IOException {
int byteCount = 0;
byte[] buffer = new byte[BUFFER_SIZE];
int bytesRead;
while ((bytesRead = in.read(buffer)) != -1) {
out.write(buffer, 0, bytesRead);
byteCount += bytesRead;
}
out.flush();
return byteCount;
}
/**
* Copy a range of content of the given InputStream to the given OutputStream.
*
If the specified range exceeds the length of the InputStream, this copies
* up to the end of the stream and returns the actual number of copied bytes.
*
Leaves both streams open when done.
* @param in the InputStream to copy from
* @param out the OutputStream to copy to
* @param start the position to start copying from
* @param end the position to end copying
* @return the number of bytes copied
* @throws IOException in case of I/O errors
* @since 4.3
*/
public static long copyRange(InputStream in, OutputStream out, long start, long end) throws IOException {
long skipped = in.skip(start);
if (skipped < start) {
throw new IOException("Skipped only " + skipped + " bytes out of " + start + " required");
}
long bytesToCopy = end - start + 1;
byte[] buffer = new byte[(int) Math.min(StreamUtils.BUFFER_SIZE, bytesToCopy)];
while (bytesToCopy > 0) {
int bytesRead = in.read(buffer);
if (bytesRead == -1) {
break;
}
else if (bytesRead <= bytesToCopy) {
out.write(buffer, 0, bytesRead);
bytesToCopy -= bytesRead;
}
else {
out.write(buffer, 0, (int) bytesToCopy);
bytesToCopy = 0;
}
}
return (end - start + 1 - bytesToCopy);
}
/**
* Drain the remaining content of the given InputStream.
*
Leaves the InputStream open when done.
* @param in the InputStream to drain
* @return the number of bytes read
* @throws IOException in case of I/O errors
* @since 4.3
*/
public static int drain(InputStream in) throws IOException {
byte[] buffer = new byte[BUFFER_SIZE];
int bytesRead = -1;
int byteCount = 0;
while ((bytesRead = in.read(buffer)) != -1) {
byteCount += bytesRead;
}
return byteCount;
}
/**
* Return an efficient empty {@link InputStream}.
* @return a {@link ByteArrayInputStream} based on an empty byte array
* @since 4.2.2
*/
public static InputStream emptyInput() {
return new ByteArrayInputStream(EMPTY_CONTENT);
}
/**
* Return a variant of the given {@link InputStream} where calling
* {@link InputStream#close() close()} has no effect.
* @param in the InputStream to decorate
* @return a version of the InputStream that ignores calls to close
*/
public static InputStream nonClosing(InputStream in) {
return new NonClosingInputStream(in);
}
/**
* Return a variant of the given {@link OutputStream} where calling
* {@link OutputStream#close() close()} has no effect.
* @param out the OutputStream to decorate
* @return a version of the OutputStream that ignores calls to close
*/
public static OutputStream nonClosing(OutputStream out) {
return new NonClosingOutputStream(out);
}
private static class NonClosingInputStream extends FilterInputStream {
public NonClosingInputStream(InputStream in) {
super(in);
}
@Override
public void close() throws IOException {
}
}
private static class NonClosingOutputStream extends FilterOutputStream {
public NonClosingOutputStream(OutputStream out) {
super(out);
}
@Override
public void write(byte[] b, int off, int let) throws IOException {
// It is critical that we override this method for performance
this.out.write(b, off, let);
}
@Override
public void close() throws IOException {
}
}
}