org.springframework.util.StreamUtils Maven / Gradle / Ivy
/*
* Copyright 2002-2017 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.util;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.FilterInputStream;
import java.io.FilterOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.Writer;
import java.nio.charset.Charset;
/**
* Simple utility methods for dealing with streams. The copy methods of this class are
* similar to those defined in {@link 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
* @see FileCopyUtils
*/
public abstract class StreamUtils {
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)
* @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();
InputStreamReader reader = new InputStreamReader(in, charset);
char[] buffer = new char[BUFFER_SIZE];
int bytesRead = -1;
while ((bytesRead = reader.read(buffer)) != -1) {
out.append(buffer, 0, bytesRead);
}
return out.toString();
}
/**
* 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 {
Assert.notNull(in, "No input byte array specified");
Assert.notNull(out, "No OutputStream specified");
out.write(in);
}
/**
* Copy the contents of the given String to the given output 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 {
Assert.notNull(in, "No input String specified");
Assert.notNull(charset, "No charset specified");
Assert.notNull(out, "No OutputStream specified");
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 {
Assert.notNull(in, "No InputStream specified");
Assert.notNull(out, "No OutputStream specified");
int byteCount = 0;
byte[] buffer = new byte[BUFFER_SIZE];
int bytesRead = -1;
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 {
Assert.notNull(in, "No InputStream specified");
Assert.notNull(out, "No OutputStream specified");
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[StreamUtils.BUFFER_SIZE];
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 {
Assert.notNull(in, "No InputStream specified");
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) {
Assert.notNull(in, "No InputStream specified");
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) {
Assert.notNull(out, "No OutputStream specified");
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
out.write(b, off, let);
}
@Override
public void close() throws IOException {
}
}
}