org.apache.commons.io.CopyUtils Maven / Gradle / Ivy
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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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
*
* http://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.apache.commons.io;
import static org.apache.commons.io.IOUtils.EOF;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.Reader;
import java.io.StringReader;
import java.io.Writer;
import java.nio.charset.Charset;
/**
* This class provides static utility methods for buffered
* copying between sources ({@link InputStream}, {@link Reader},
* {@link String} and {@code byte[]}) and destinations
* ({@link OutputStream}, {@link Writer}, {@link String} and
* {@code byte[]}).
*
* Unless otherwise noted, these {@code copy} methods do not
* flush or close the streams. Often doing so would require making non-portable
* assumptions about the streams' origin and further use. This means that both
* streams' {@code close()} methods must be called after copying. if one
* omits this step, then the stream resources (sockets, file descriptors) are
* released when the associated Stream is garbage-collected. It is not a good
* idea to rely on this mechanism. For a good overview of the distinction
* between "memory management" and "resource management", see
* this
* UnixReview article.
*
* For byte-to-char methods, a {@code copy} variant allows the encoding
* to be selected (otherwise the platform default is used). We would like to
* encourage you to always specify the encoding because relying on the platform
* default can lead to unexpected results.
*
* We don't provide special variants for the {@code copy} methods that
* let you specify the buffer size because in modern VMs the impact on speed
* seems to be minimal. We're using a default buffer size of 4 KB.
*
* The {@code copy} methods use an internal buffer when copying. It is
* therefore advisable not to deliberately wrap the stream arguments
* to the {@code copy} methods in {@code Buffered*} streams. For
* example, don't do the following:
*
* copy( new BufferedInputStream( in ), new BufferedOutputStream( out ) );
*
* The rationale is as follows:
*
* Imagine that an InputStream's read() is a very expensive operation, which
* would usually suggest wrapping in a BufferedInputStream. The
* BufferedInputStream works by issuing infrequent
* {@link java.io.InputStream#read(byte[] b, int off, int len)} requests on the
* underlying InputStream, to fill an internal buffer, from which further
* {@code read} requests can inexpensively get their data (until the buffer
* runs out).
*
* However, the {@code copy} methods do the same thing, keeping an
* internal buffer, populated by
* {@link InputStream#read(byte[] b, int off, int len)} requests. Having two
* buffers (or three if the destination stream is also buffered) is pointless,
* and the unnecessary buffer management hurts performance slightly (about 3%,
* according to some simple experiments).
*
* Behold, intrepid explorers; a map of this class:
*
* Method Input Output Dependency
* ------ ----- ------ -------
* 1 copy InputStream OutputStream (primitive)
* 2 copy Reader Writer (primitive)
*
* 3 copy InputStream Writer 2
*
* 4 copy Reader OutputStream 2
*
* 5 copy String OutputStream 2
* 6 copy String Writer (trivial)
*
* 7 copy byte[] Writer 3
* 8 copy byte[] OutputStream (trivial)
*
*
* Note that only the first two methods shuffle bytes; the rest use these
* two, or (if possible) copy using native Java copy methods. As there are
* method variants to specify the encoding, each row may
* correspond to up to 2 methods.
*
* Provenance: Excalibur.
*
* @deprecated Use IOUtils. Will be removed in 3.0.
* Methods renamed to IOUtils.write() or IOUtils.copy().
* Null handling behavior changed in IOUtils (null data does not
* throw NullPointerException).
*/
@Deprecated
public class CopyUtils {
/**
* Copies bytes from a {@code byte[]} to an {@link OutputStream}.
* @param input the byte array to read from
* @param output the {@link OutputStream} to write to
* @throws IOException In case of an I/O problem
*/
public static void copy(final byte[] input, final OutputStream output) throws IOException {
output.write(input);
}
/**
* Copies and convert bytes from a {@code byte[]} to chars on a
* {@link Writer}.
* The platform's default encoding is used for the byte-to-char conversion.
*
* @param input the byte array to read from
* @param output the {@link Writer} to write to
* @throws IOException In case of an I/O problem
* @deprecated Use {@link #copy(byte[], Writer, String)} instead
*/
@Deprecated
public static void copy(final byte[] input, final Writer output) throws IOException {
final ByteArrayInputStream inputStream = new ByteArrayInputStream(input);
copy(inputStream, output);
}
/**
* Copies and convert bytes from a {@code byte[]} to chars on a
* {@link Writer}, using the specified encoding.
*
* @param input the byte array to read from
* @param output the {@link Writer} to write to
* @param encoding The name of a supported character encoding. See the
* IANA
* Charset Registry for a list of valid encoding types.
* @throws IOException In case of an I/O problem
*/
public static void copy(final byte[] input, final Writer output, final String encoding) throws IOException {
final ByteArrayInputStream inputStream = new ByteArrayInputStream(input);
copy(inputStream, output, encoding);
}
/**
* Copies bytes from an {@link InputStream} to an
* {@link OutputStream}.
*
* @param input the {@link InputStream} to read from
* @param output the {@link OutputStream} to write to
* @return the number of bytes copied
* @throws IOException In case of an I/O problem
*/
public static int copy(final InputStream input, final OutputStream output) throws IOException {
final byte[] buffer = IOUtils.byteArray();
int count = 0;
int n;
while (EOF != (n = input.read(buffer))) {
output.write(buffer, 0, n);
count += n;
}
return count;
}
/**
* Copies and convert bytes from an {@link InputStream} to chars on a
* {@link Writer}.
* The platform's default encoding is used for the byte-to-char conversion.
*
* @param input the {@link InputStream} to read from
* @param output the {@link Writer} to write to
* @throws IOException In case of an I/O problem
* @deprecated Use {@link #copy(InputStream, Writer, String)} instead
*/
@Deprecated
public static void copy(
final InputStream input,
final Writer output)
throws IOException {
// make explicit the dependency on the default encoding
final InputStreamReader in = new InputStreamReader(input, Charset.defaultCharset());
copy(in, output);
}
/**
* Copies and convert bytes from an {@link InputStream} to chars on a
* {@link Writer}, using the specified encoding.
*
* @param input the {@link InputStream} to read from
* @param output the {@link Writer} to write to
* @param encoding The name of a supported character encoding. See the
* IANA
* Charset Registry for a list of valid encoding types.
* @throws IOException In case of an I/O problem
*/
public static void copy(
final InputStream input,
final Writer output,
final String encoding)
throws IOException {
final InputStreamReader in = new InputStreamReader(input, encoding);
copy(in, output);
}
/**
* Serialize chars from a {@link Reader} to bytes on an
* {@link OutputStream}, and flush the {@link OutputStream}.
* Uses the default platform encoding.
*
* @param input the {@link Reader} to read from
* @param output the {@link OutputStream} to write to
* @throws IOException In case of an I/O problem
* @deprecated Use {@link #copy(Reader, OutputStream, String)} instead
*/
@Deprecated
public static void copy(
final Reader input,
final OutputStream output)
throws IOException {
// make explicit the dependency on the default encoding
final OutputStreamWriter out = new OutputStreamWriter(output, Charset.defaultCharset());
copy(input, out);
// XXX Unless anyone is planning on rewriting OutputStreamWriter, we
// have to flush here.
out.flush();
}
/**
* Serialize chars from a {@link Reader} to bytes on an
* {@link OutputStream}, and flush the {@link OutputStream}.
*
* @param input the {@link Reader} to read from
* @param output the {@link OutputStream} to write to
* @param encoding The name of a supported character encoding. See the
* IANA
* Charset Registry for a list of valid encoding types.
* @throws IOException In case of an I/O problem
* @since 2.5
*/
public static void copy(
final Reader input,
final OutputStream output,
final String encoding)
throws IOException {
final OutputStreamWriter out = new OutputStreamWriter(output, encoding);
copy(input, out);
// XXX Unless anyone is planning on rewriting OutputStreamWriter, we
// have to flush here.
out.flush();
}
/**
* Copies chars from a {@link Reader} to a {@link Writer}.
*
* @param input the {@link Reader} to read from
* @param output the {@link Writer} to write to
* @return the number of characters copied
* @throws IOException In case of an I/O problem
*/
public static int copy(
final Reader input,
final Writer output)
throws IOException {
final char[] buffer = IOUtils.getScratchCharArray();
int count = 0;
int n;
while (EOF != (n = input.read(buffer))) {
output.write(buffer, 0, n);
count += n;
}
return count;
}
/**
* Serialize chars from a {@link String} to bytes on an
* {@link OutputStream}, and
* flush the {@link OutputStream}.
* Uses the platform default encoding.
*
* @param input the {@link String} to read from
* @param output the {@link OutputStream} to write to
* @throws IOException In case of an I/O problem
* @deprecated Use {@link #copy(String, OutputStream, String)} instead
*/
@Deprecated
public static void copy(
final String input,
final OutputStream output)
throws IOException {
final StringReader in = new StringReader(input);
// make explicit the dependency on the default encoding
final OutputStreamWriter out = new OutputStreamWriter(output, Charset.defaultCharset());
copy(in, out);
// XXX Unless anyone is planning on rewriting OutputStreamWriter, we
// have to flush here.
out.flush();
}
/**
* Serialize chars from a {@link String} to bytes on an
* {@link OutputStream}, and
* flush the {@link OutputStream}.
*
* @param input the {@link String} to read from
* @param output the {@link OutputStream} to write to
* @param encoding The name of a supported character encoding. See the
* IANA
* Charset Registry for a list of valid encoding types.
* @throws IOException In case of an I/O problem
* @since 2.5
*/
public static void copy(
final String input,
final OutputStream output,
final String encoding)
throws IOException {
final StringReader in = new StringReader(input);
final OutputStreamWriter out = new OutputStreamWriter(output, encoding);
copy(in, out);
// XXX Unless anyone is planning on rewriting OutputStreamWriter, we
// have to flush here.
out.flush();
}
/**
* Copies chars from a {@link String} to a {@link Writer}.
*
* @param input the {@link String} to read from
* @param output the {@link Writer} to write to
* @throws IOException In case of an I/O problem
*/
public static void copy(final String input, final Writer output)
throws IOException {
output.write(input);
}
/**
* Instances should NOT be constructed in standard programming.
*
* @deprecated TODO Make private in 3.0.
*/
@Deprecated
public CopyUtils() {
// empty
}
}