org.apache.maven.shared.utils.io.IOUtil Maven / Gradle / Ivy
package org.apache.maven.shared.utils.io;
/*
* 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.
*/
import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import java.io.BufferedInputStream;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
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.StringWriter;
import java.io.Writer;
import java.nio.channels.Channel;
/**
* General IO Stream manipulation.
*
* This class provides static utility methods for input/output operations, particularly buffered
* copying between sources (InputStream, Reader, String and
* byte[]) and destinations (OutputStream, Writer,
* String and byte[]).
*
*
* Unless otherwise noted, these 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' 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 each copy method, a variant is provided that allows the caller to specify the
* buffer size (the default is 4k). As the buffer size can have a fairly large impact on speed, this
* may be worth tweaking. Often "large buffer -> faster" does not hold, even for large data
* transfers.
*
* For byte-to-char methods, a copy variant allows the encoding to be selected
* (otherwise the platform default is used).
*
* The copy methods use an internal buffer when copying. It is therefore advisable
* not to deliberately wrap the stream arguments to the copy methods in
* 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 read requests can inexpensively get
* their data (until the buffer runs out).
* However, the 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).
*
* @author Peter Donald
* @author Jeff Turner
* @version CVS $Revision: 1750548 $ $Date: 2016-06-28 19:32:21 +0200 (Tue, 28 Jun 2016) $
*
*/
public final class IOUtil
/*
* 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 toString InputStream String 3
* 5 toByteArray InputStream byte[] 1
*
* 6 copy Reader OutputStream 2
* 7 toString Reader String 2
* 8 toByteArray Reader byte[] 6
*
* 9 copy String OutputStream 2
* 10 copy String Writer (trivial)
* 11 toByteArray String byte[] 9
*
* 12 copy byte[] Writer 3
* 13 toString byte[] String 12
* 14 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 buffer size and encoding,
* each row may correspond to up to 4 methods.
*
*/
{
private static final int DEFAULT_BUFFER_SIZE = 1024 * 4;
/**
* Private constructor to prevent instantiation.
*/
private IOUtil()
{
}
///////////////////////////////////////////////////////////////
// Core copy methods
///////////////////////////////////////////////////////////////
/**
* Copy bytes from an InputStream to an OutputStream.
* @param input The input size.
* @param output The resulting output.
* @throws IOException in case of an error.
*/
public static void copy( @Nonnull final InputStream input, @Nonnull final OutputStream output )
throws IOException
{
copy( input, output, DEFAULT_BUFFER_SIZE );
}
/**
* Copy bytes from an InputStream to an OutputStream.
*
* @param input The input size.
* @param output The resulting output.
* @param bufferSize Size of internal buffer to use.
* @throws IOException in case of an error.
*/
public static void copy( @Nonnull final InputStream input, @Nonnull final OutputStream output,
final int bufferSize )
throws IOException
{
final byte[] buffer = new byte[bufferSize];
int n;
while ( -1 != ( n = input.read( buffer ) ) )
{
output.write( buffer, 0, n );
}
}
/**
* Copy chars from a Reader to a Writer.
* @param input The input size.
* @param output The resulting output.
* @throws IOException in case of failure.
*/
public static void copy( @Nonnull final Reader input, @Nonnull final Writer output )
throws IOException
{
copy( input, output, DEFAULT_BUFFER_SIZE );
}
/**
* Copy chars from a Reader to a Writer.
*
* @param input The input size.
* @param output The resulting output.
* @param bufferSize Size of internal buffer to use.
* @throws IOException in case of failure.
*/
public static void copy( @Nonnull final Reader input, @Nonnull final Writer output, final int bufferSize )
throws IOException
{
final char[] buffer = new char[bufferSize];
int n;
while ( -1 != ( n = input.read( buffer ) ) )
{
output.write( buffer, 0, n );
}
output.flush();
}
///////////////////////////////////////////////////////////////
// Derived copy methods
// InputStream -> *
///////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////
// InputStream -> Writer
/**
* Copy and convert bytes from an InputStream to chars on a
* Writer.
* The platform's default encoding is used for the byte-to-char conversion.
* @param input The input size.
* @param output The resulting output.
* @throws IOException in case of failure.
*/
public static void copy( @Nonnull final InputStream input, @Nonnull final Writer output )
throws IOException
{
copy( input, output, DEFAULT_BUFFER_SIZE );
}
/**
* Copy and convert bytes from an InputStream to chars on a
* Writer.
* The platform's default encoding is used for the byte-to-char conversion.
*
* @param input The input size.
* @param output The resulting output.
* @param bufferSize Size of internal buffer to use.
* @throws IOException in case of failure.
*/
public static void copy( @Nonnull final InputStream input, @Nonnull final Writer output, final int bufferSize )
throws IOException
{
final InputStreamReader in = new InputStreamReader( input );
copy( in, output, bufferSize );
}
/**
* Copy and convert bytes from an InputStream to chars on a
* Writer, using the specified encoding.
*
* @param input The input size.
* @param output The resulting output.
* @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 failure.
*/
public static void copy( @Nonnull final InputStream input, @Nonnull final Writer output,
@Nonnull final String encoding )
throws IOException
{
final InputStreamReader in = new InputStreamReader( input, encoding );
copy( in, output );
}
/**
* Copy and convert bytes from an InputStream to chars on a
* Writer, using the specified encoding.
*
* @param encoding The name of a supported character encoding. See the
* IANA
* Charset Registry for a list of valid encoding types.
* @param input The input size.
* @param output The resulting output.
* @param bufferSize Size of internal buffer to use.
* @throws IOException in case of failure.
*/
public static void copy( @Nonnull final InputStream input, @Nonnull final Writer output,
@Nonnull final String encoding, final int bufferSize )
throws IOException
{
final InputStreamReader in = new InputStreamReader( input, encoding );
copy( in, output, bufferSize );
}
///////////////////////////////////////////////////////////////
// InputStream -> String
/**
* Get the contents of an InputStream as a String.
* The platform's default encoding is used for the byte-to-char conversion.
* @param input The input size.
* @return The resulting string.
* @throws IOException in case of failure.
*/
@Nonnull public static String toString( @Nonnull final InputStream input )
throws IOException
{
return toString( input, DEFAULT_BUFFER_SIZE );
}
/**
* Get the contents of an InputStream as a String.
* The platform's default encoding is used for the byte-to-char conversion.
*
* @param input The input size.
* @param bufferSize Size of internal buffer to use.
* @return the resulting string.
* @throws IOException in case of failure.
*/
@Nonnull public static String toString( @Nonnull final InputStream input, final int bufferSize )
throws IOException
{
final StringWriter sw = new StringWriter();
copy( input, sw, bufferSize );
return sw.toString();
}
/**
* Get the contents of an InputStream as a String.
*
* @param input The input size.
* @param encoding The name of a supported character encoding. See the
* IANA
* Charset Registry for a list of valid encoding types.
* @return the converted string.
* @throws IOException in case of failure.
*/
@Nonnull public static String toString( @Nonnull final InputStream input, @Nonnull final String encoding )
throws IOException
{
return toString( input, encoding, DEFAULT_BUFFER_SIZE );
}
/**
* Get the contents of an InputStream as a String.
*
* @param input The input size.
* @param encoding The name of a supported character encoding. See the
* IANA
* Charset Registry for a list of valid encoding types.
* @param bufferSize Size of internal buffer to use.
* @return The converted string.
* @throws IOException in case of failure.
*/
@Nonnull public static String toString( @Nonnull final InputStream input, @Nonnull final String encoding,
final int bufferSize )
throws IOException
{
final StringWriter sw = new StringWriter();
copy( input, sw, encoding, bufferSize );
return sw.toString();
}
///////////////////////////////////////////////////////////////
// InputStream -> byte[]
/**
* Get the contents of an InputStream as a byte[].
* @param input The input size.
* @return the resulting byte array.
* @throws IOException in case of failure.
*/
@Nonnull public static byte[] toByteArray( @Nonnull final InputStream input )
throws IOException
{
return toByteArray( input, DEFAULT_BUFFER_SIZE );
}
/**
* Get the contents of an InputStream as a byte[].
*
* @param input The input size.
* @param bufferSize Size of internal buffer to use.
* @return the resulting byte array.
* @throws IOException in case of failure.
*/
@Nonnull public static byte[] toByteArray( @Nonnull final InputStream input, final int bufferSize )
throws IOException
{
final ByteArrayOutputStream output = new ByteArrayOutputStream();
copy( input, output, bufferSize );
return output.toByteArray();
}
///////////////////////////////////////////////////////////////
// Derived copy methods
// Reader -> *
///////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////
// Reader -> OutputStream
/**
* Serialize chars from a Reader to bytes on an OutputStream, and
* flush the OutputStream.
* @param input The input size.
* @param output The resulting output.
* @throws IOException in case of failure.
*/
public static void copy( @Nonnull final Reader input, @Nonnull final OutputStream output )
throws IOException
{
copy( input, output, DEFAULT_BUFFER_SIZE );
}
/**
* Serialize chars from a Reader to bytes on an OutputStream, and
* flush the OutputStream.
*
* @param input The input size.
* @param output The resulting output.
* @param bufferSize Size of internal buffer to use.
* @throws IOException in case of failure.
*/
public static void copy( @Nonnull final Reader input, @Nonnull final OutputStream output, final int bufferSize )
throws IOException
{
final OutputStreamWriter out = new OutputStreamWriter( output );
copy( input, out, bufferSize );
// NOTE: Unless anyone is planning on rewriting OutputStreamWriter, we have to flush
// here.
out.flush();
}
///////////////////////////////////////////////////////////////
// Reader -> String
/**
* Get the contents of a Reader as a String.
* @param input The input size.
* @return The converted string.
* @throws IOException in case of failure.
*/
@Nonnull public static String toString( @Nonnull final Reader input )
throws IOException
{
return toString( input, DEFAULT_BUFFER_SIZE );
}
/**
* Get the contents of a Reader as a String.
*
* @param input The input size.
* @param bufferSize Size of internal buffer to use.
* @return the resulting byte array.
* @throws IOException in case of failure.
*/
@Nonnull public static String toString( @Nonnull final Reader input, final int bufferSize )
throws IOException
{
final StringWriter sw = new StringWriter();
copy( input, sw, bufferSize );
return sw.toString();
}
///////////////////////////////////////////////////////////////
// Reader -> byte[]
/**
* Get the contents of a Reader as a byte[].
* @param input The input size.
* @return the resulting byte array.
* @throws IOException in case of failure.
*/
@Nonnull public static byte[] toByteArray( @Nonnull final Reader input )
throws IOException
{
return toByteArray( input, DEFAULT_BUFFER_SIZE );
}
/**
* Get the contents of a Reader as a byte[].
*
* @param input The input size.
* @param bufferSize Size of internal buffer to use.
* @return the resulting byte array.
* @throws IOException in case of failure.
*/
@Nonnull public static byte[] toByteArray( @Nonnull final Reader input, final int bufferSize )
throws IOException
{
ByteArrayOutputStream output = new ByteArrayOutputStream();
copy( input, output, bufferSize );
return output.toByteArray();
}
///////////////////////////////////////////////////////////////
// Derived copy methods
// String -> *
///////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////
// String -> OutputStream
/**
* Serialize chars from a String to bytes on an OutputStream, and
* flush the OutputStream.
* @param input The input size.
* @param output The resulting output.
* @throws IOException in case of failure.
*/
public static void copy( @Nonnull final String input, @Nonnull final OutputStream output )
throws IOException
{
copy( input, output, DEFAULT_BUFFER_SIZE );
}
/**
* Serialize chars from a String to bytes on an OutputStream, and
* flush the OutputStream.
*
* @param input The input size.
* @param output The resulting output.
* @param bufferSize Size of internal buffer to use.
* @throws IOException in case of failure.
*/
public static void copy( @Nonnull final String input, @Nonnull final OutputStream output, final int bufferSize )
throws IOException
{
final StringReader in = new StringReader( input );
final OutputStreamWriter out = new OutputStreamWriter( output );
copy( in, out, bufferSize );
// NOTE: Unless anyone is planning on rewriting OutputStreamWriter, we have to flush
// here.
out.flush();
}
///////////////////////////////////////////////////////////////
// String -> Writer
/**
* Copy chars from a String to a Writer.
* @param input Input string.
* @param output resulting output {@link Writer}
* @throws IOException in case of failure.
*/
public static void copy( @Nonnull final String input, @Nonnull final Writer output )
throws IOException
{
output.write( input );
}
///////////////////////////////////////////////////////////////
// String -> byte[]
/**
* Get the contents of a String as a byte[].
* @param input The input size.
* @return The resulting byte array.
* @throws IOException in case of failure.
*/
@Nonnull public static byte[] toByteArray( @Nonnull final String input )
throws IOException
{
return toByteArray( input, DEFAULT_BUFFER_SIZE );
}
/**
* Get the contents of a String as a byte[].
*
* @param input The input size.
* @param bufferSize Size of internal buffer to use.
* @return The resulting byte array.
* @throws IOException in case of failure.
*/
@Nonnull public static byte[] toByteArray( @Nonnull final String input, final int bufferSize )
throws IOException
{
ByteArrayOutputStream output = new ByteArrayOutputStream();
copy( input, output, bufferSize );
return output.toByteArray();
}
///////////////////////////////////////////////////////////////
// Derived copy methods
// byte[] -> *
///////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////
// byte[] -> Writer
/**
* Copy and convert bytes from a byte[] to chars on a
* Writer.
* The platform's default encoding is used for the byte-to-char conversion.
* @param input The input size.
* @param output The resulting output.
* @throws IOException in case of failure.
*/
public static void copy( @Nonnull final byte[] input, @Nonnull final Writer output )
throws IOException
{
copy( input, output, DEFAULT_BUFFER_SIZE );
}
/**
* Copy and convert bytes from a byte[] to chars on a
* Writer.
* The platform's default encoding is used for the byte-to-char conversion.
*
* @param input The input size.
* @param output The resulting output.
* @param bufferSize Size of internal buffer to use.
* @throws IOException in case of failure.
*/
public static void copy( @Nonnull final byte[] input, @Nonnull final Writer output, final int bufferSize )
throws IOException
{
final ByteArrayInputStream in = new ByteArrayInputStream( input );
copy( in, output, bufferSize );
}
/**
* Copy and convert bytes from a byte[] to chars on a
* Writer, using the specified encoding.
*
* @param encoding The name of a supported character encoding. See the
* IANA
* Charset Registry for a list of valid encoding types.
* @param input The input size.
* @param output The resulting output.
* @throws IOException in case of failure.
*/
public static void copy( @Nonnull final byte[] input, @Nonnull final Writer output, final String encoding )
throws IOException
{
final ByteArrayInputStream in = new ByteArrayInputStream( input );
copy( in, output, encoding );
}
/**
* Copy and convert bytes from a byte[] to chars on a
* Writer, using the specified encoding.
*
* @param encoding The name of a supported character encoding. See the
* IANA
* Charset Registry for a list of valid encoding types.
* @param input The input bytes.
* @param output The output buffer {@link Writer}
* @param bufferSize Size of internal buffer to use.
* @throws IOException in case of failure.
*/
public static void copy( @Nonnull final byte[] input, @Nonnull final Writer output, @Nonnull final String encoding,
final int bufferSize )
throws IOException
{
final ByteArrayInputStream in = new ByteArrayInputStream( input );
copy( in, output, encoding, bufferSize );
}
///////////////////////////////////////////////////////////////
// byte[] -> String
/**
* Get the contents of a byte[] as a String.
* The platform's default encoding is used for the byte-to-char conversion.
* @param input The input bytes.
* @return The resulting string.
* @throws IOException in case of failure.
*/
@Nonnull public static String toString( @Nonnull final byte[] input )
throws IOException
{
return toString( input, DEFAULT_BUFFER_SIZE );
}
/**
* Get the contents of a byte[] as a String.
* The platform's default encoding is used for the byte-to-char conversion.
*
* @param bufferSize Size of internal buffer to use.
* @param input The input bytes.
* @return The created string.
* @throws IOException in case of failure.
*/
@Nonnull public static String toString( @Nonnull final byte[] input, final int bufferSize )
throws IOException
{
final StringWriter sw = new StringWriter();
copy( input, sw, bufferSize );
return sw.toString();
}
/**
* Get the contents of a byte[] as a String.
*
* @param encoding The name of a supported character encoding. See the
* IANA
* Charset Registry for a list of valid encoding types.
* @param input The input bytes.
* @return The resulting string.
* @throws IOException in case of failure.
*/
@Nonnull public static String toString( @Nonnull final byte[] input, @Nonnull final String encoding )
throws IOException
{
return toString( input, encoding, DEFAULT_BUFFER_SIZE );
}
/**
* Get the contents of a byte[] as a String.
*
* @param encoding The name of a supported character encoding. See the
* IANA
* Charset Registry for a list of valid encoding types.
* @param bufferSize Size of internal buffer to use.
* @param input Input bytes.
* @return The resulting string.
* @throws IOException in case of failure.
*/
@Nonnull public static String toString( @Nonnull final byte[] input, @Nonnull final String encoding,
final int bufferSize )
throws IOException
{
final StringWriter sw = new StringWriter();
copy( input, sw, encoding, bufferSize );
return sw.toString();
}
///////////////////////////////////////////////////////////////
// byte[] -> OutputStream
/**
* Copy bytes from a byte[] to an OutputStream.
* @param input Input byte array.
* @param output output stream {@link OutputStream}
* @throws IOException in case of failure.
*/
public static void copy( @Nonnull final byte[] input, @Nonnull final OutputStream output )
throws IOException
{
output.write( input );
}
/**
* Compare the contents of two Streams to determine if they are equal or not.
*
* @param input1 the first stream
* @param input2 the second stream
* @return true if the content of the streams are equal or they both don't exist, false otherwise
* @throws IOException in case of failure.
*/
public static boolean contentEquals( @Nonnull final InputStream input1, @Nonnull final InputStream input2 )
throws IOException
{
final InputStream bufferedInput1 = new BufferedInputStream( input1 );
final InputStream bufferedInput2 = new BufferedInputStream( input2 );
int ch = bufferedInput1.read();
while ( -1 != ch )
{
final int ch2 = bufferedInput2.read();
if ( ch != ch2 )
{
return false;
}
ch = bufferedInput1.read();
}
final int ch2 = bufferedInput2.read();
return -1 == ch2;
}
// ----------------------------------------------------------------------
// closeXXX()
// ----------------------------------------------------------------------
/**
* Closes a {@code Channel} suppressing any {@code IOException}.
*
* Note:
The usecase justifying this method is a shortcoming of the Java language up to but not including
* Java 7. For any code targetting Java 7 or later use of this method is highly discouraged and the
* {@code try-with-resources} statement should be used instead. Care must be taken to not use this method in a way
* {@code IOException}s get suppressed incorrectly.
* You must close all resources in use inside the {@code try} block to not suppress exceptions in the
* {@code finally} block incorrectly by using this method.
*
*
* Example:
*
* // Introduce variables for the resources and initialize them to null. This cannot throw an exception.
* Closeable resource1 = null;
* Closeable resource2 = null;
* try
* {
* // Obtain a resource object and assign it to variable resource1. This may throw an exception.
* // If successful, resource1 != null.
* resource1 = ...
*
* // Obtain a resource object and assign it to variable resource2. This may throw an exception.
* // If successful, resource2 != null. Not reached if an exception has been thrown above.
* resource2 = ...
*
* // Perform operations on the resources. This may throw an exception. Not reached if an exception has been
* // thrown above. Note: Treat the variables resource1 and resource2 the same way as if they would have been
* // declared with the final modifier - that is - do NOT write anyting like resource1 = something else or
* // resource2 = something else here.
* resource1 ...
* resource2 ...
*
* // Finally, close the resources and set the variables to null indicating successful completion.
* // This may throw an exception. Not reached if an exception has been thrown above.
* resource1.close();
* resource1 = null;
* // Not reached if an exception has been thrown above.
* resource2.close();
* resource2 = null;
*
* // All resources are closed at this point and all operations (up to here) completed successfully without
* // throwing an exception we would need to handle (by letting it propagate or by catching and handling it).
* }
* finally
* {
* // Cleanup any resource not closed in the try block due to an exception having been thrown and suppress any
* // exception this may produce to not stop the exception from the try block to be propagated. If the try
* // block completed successfully, all variables will have been set to null there and this will not do
* // anything. This is just to cleanup properly in case of an exception.
*
* IOUtil.close( resource1 );
* IOUtil.close( resource2 );
*
* // Without that utility method you would need to write the following:
* //
* // try
* // {
* // if ( resource1 != null )
* // {
* // resource1.close();
* // }
* // }
* // catch( IOException e )
* // {
* // Suppressed. If resource1 != null, an exception has already been thrown in the try block we need to
* // propagate instead of this one.
* // }
* // finally
* // {
* // try
* // {
* // if ( resource2 != null )
* // {
* // resource2.close();
* // }
* // }
* // catch ( IOException e )
* // {
* // Suppressed. If resource2 != null, an exception has already been thrown in the try block we need to
* // propagate instead of this one.
* // }
* // }
* }
*
*
*
* @param channel The channel to close or {@code null}.
*/
public static void close( @Nullable Channel channel )
{
try
{
if ( channel != null )
{
channel.close();
}
}
catch ( IOException ex )
{
// Suppressed
}
}
/**
* Closes an {@code InputStream} suppressing any {@code IOException}.
*
* Note:
The usecase justifying this method is a shortcoming of the Java language up to but not including
* Java 7. For any code targeting Java 7 or later use of this method is highly discouraged and the
* {@code try-with-resources} statement should be used instead. Care must be taken to not use this method in a way
* {@code IOException}s get suppressed incorrectly.
* You must close all resources in use inside the {@code try} block to not suppress exceptions in the
* {@code finally} block incorrectly by using this method.
*
*
* Example:
*
* // Introduce variables for the resources and initialize them to null. This cannot throw an exception.
* Closeable resource1 = null;
* Closeable resource2 = null;
* try
* {
* // Obtain a resource object and assign it to variable resource1. This may throw an exception.
* // If successful, resource1 != null.
* resource1 = ...
*
* // Obtain a resource object and assign it to variable resource2. This may throw an exception.
* // If successful, resource2 != null. Not reached if an exception has been thrown above.
* resource2 = ...
*
* // Perform operations on the resources. This may throw an exception. Not reached if an exception has been
* // thrown above. Note: Treat the variables resource1 and resource2 the same way as if they would have been
* // declared with the final modifier - that is - do NOT write anyting like resource1 = something else or
* // resource2 = something else here.
* resource1 ...
* resource2 ...
*
* // Finally, close the resources and set the variables to null indicating successful completion.
* // This may throw an exception. Not reached if an exception has been thrown above.
* resource1.close();
* resource1 = null;
* // This may throw an exception. Not reached if an exception has been thrown above.
* resource2.close();
* resource2 = null;
*
* // All resources are closed at this point and all operations (up to here) completed successfully without
* // throwing an exception we would need to handle (by letting it propagate or by catching and handling it).
* }
* finally
* {
* // Cleanup any resource not closed in the try block due to an exception having been thrown and suppress any
* // exception this may produce to not stop the exception from the try block to be propagated. If the try
* // block completed successfully, all variables will have been set to null there and this will not do
* // anything. This is just to cleanup properly in case of an exception.
*
* IOUtil.close( resource1 );
* IOUtil.close( resource2 );
*
* // Without that utility method you would need to write the following:
* //
* // try
* // {
* // if ( resource1 != null )
* // {
* // resource1.close();
* // }
* // }
* // catch( IOException e )
* // {
* // Suppressed. If resource1 != null, an exception has already been thrown in the try block we need to
* // propagate instead of this one.
* // }
* // finally
* // {
* // try
* // {
* // if ( resource2 != null )
* // {
* // resource2.close();
* // }
* // }
* // catch ( IOException e )
* // {
* // Suppressed. If resource2 != null, an exception has already been thrown in the try block we need to
* // propagate instead of this one.
* // }
* // }
* }
*
*
*
* @param inputStream The stream to close or {@code null}.
*/
public static void close( @Nullable InputStream inputStream )
{
try
{
if ( inputStream != null )
{
inputStream.close();
}
}
catch ( IOException ex )
{
// Suppressed
}
}
/**
* Closes an {@code OutputStream} suppressing any {@code IOException}.
*
* Note:
The usecase justifying this method is a shortcoming of the Java language up to but not including
* Java 7. For any code targeting Java 7 or later use of this method is highly discouraged and the
* {@code try-with-resources} statement should be used instead. Care must be taken to not use this method in a way
* {@code IOException}s get suppressed incorrectly.
* You must close all resources in use inside the {@code try} block to not suppress exceptions in the
* {@code finally} block incorrectly by using this method.
*
*
* Example:
*
* // Introduce variables for the resources and initialize them to null. This cannot throw an exception.
* Closeable resource1 = null;
* Closeable resource2 = null;
* try
* {
* // Obtain a resource object and assign it to variable resource1. This may throw an exception.
* // If successful, resource1 != null.
* resource1 = ...
*
* // Obtain a resource object and assign it to variable resource2. This may throw an exception.
* // If successful, resource2 != null. Not reached if an exception has been thrown above.
* resource2 = ...
*
* // Perform operations on the resources. This may throw an exception. Not reached if an exception has been
* // thrown above. Note: Treat the variables resource1 and resource2 the same way as if they would have been
* // declared with the final modifier - that is - do NOT write anyting like resource1 = something else or
* // resource2 = something else here.
* resource1 ...
* resource2 ...
*
* // Finally, close the resources and set the variables to null indicating successful completion.
* // This may throw an exception. Not reached if an exception has been thrown above.
* resource1.close();
* resource1 = null;
* // This may throw an exception. Not reached if an exception has been thrown above.
* resource2.close();
* resource2 = null;
*
* // All resources are closed at this point and all operations (up to here) completed successfully without
* // throwing an exception we would need to handle (by letting it propagate or by catching and handling it).
* }
* finally
* {
* // Cleanup any resource not closed in the try block due to an exception having been thrown and suppress any
* // exception this may produce to not stop the exception from the try block to be propagated. If the try
* // block completed successfully, all variables will have been set to null there and this will not do
* // anything. This is just to cleanup properly in case of an exception.
*
* IOUtil.close( resource1 );
* IOUtil.close( resource2 );
*
* // Without that utility method you would need to write the following:
* //
* // try
* // {
* // if ( resource1 != null )
* // {
* // resource1.close();
* // }
* // }
* // catch( IOException e )
* // {
* // Suppressed. If resource1 != null, an exception has already been thrown in the try block we need to
* // propagate instead of this one.
* // }
* // finally
* // {
* // try
* // {
* // if ( resource2 != null )
* // {
* // resource2.close();
* // }
* // }
* // catch ( IOException e )
* // {
* // Suppressed. If resource2 != null, an exception has already been thrown in the try block we need to
* // propagate instead of this one.
* // }
* // }
* }
*
*
*
* @param outputStream The stream to close or {@code null}.
*/
public static void close( @Nullable OutputStream outputStream )
{
try
{
if ( outputStream != null )
{
outputStream.close();
}
}
catch ( IOException ex )
{
// Suppressed
}
}
/**
* Closes a {@code Reader} suppressing any {@code IOException}.
*
* Note:
The usecase justifying this method is a shortcoming of the Java language up to but not including
* Java 7. For any code targeting Java 7 or later use of this method is highly discouraged and the
* {@code try-with-resources} statement should be used instead. Care must be taken to not use this method in a way
* {@code IOException}s get suppressed incorrectly.
* You must close all resources in use inside the {@code try} block to not suppress exceptions in the
* {@code finally} block incorrectly by using this method.
*
*
* Example:
*
* // Introduce variables for the resources and initialize them to null. This cannot throw an exception.
* Closeable resource1 = null;
* Closeable resource2 = null;
* try
* {
* // Obtain a resource object and assign it to variable resource1. This may throw an exception.
* // If successful, resource1 != null.
* resource1 = ...
*
* // Obtain a resource object and assign it to variable resource2. This may throw an exception.
* // If successful, resource2 != null. Not reached if an exception has been thrown above.
* resource2 = ...
*
* // Perform operations on the resources. This may throw an exception. Not reached if an exception has been
* // thrown above. Note: Treat the variables resource1 and resource2 the same way as if they would have been
* // declared with the final modifier - that is - do NOT write anyting like resource1 = something else or
* // resource2 = something else here.
* resource1 ...
* resource2 ...
*
* // Finally, close the resources and set the variables to null indicating successful completion.
* // This may throw an exception. Not reached if an exception has been thrown above.
* resource1.close();
* resource1 = null;
* // This may throw an exception. Not reached if an exception has been thrown above.
* resource2.close();
* resource2 = null;
*
* // All resources are closed at this point and all operations (up to here) completed successfully without
* // throwing an exception we would need to handle (by letting it propagate or by catching and handling it).
* }
* finally
* {
* // Cleanup any resource not closed in the try block due to an exception having been thrown and suppress any
* // exception this may produce to not stop the exception from the try block to be propagated. If the try
* // block completed successfully, all variables will have been set to null there and this will not do
* // anything. This is just to cleanup properly in case of an exception.
*
* IOUtil.close( resource1 );
* IOUtil.close( resource2 );
*
* // Without that utility method you would need to write the following:
* //
* // try
* // {
* // if ( resource1 != null )
* // {
* // resource1.close();
* // }
* // }
* // catch( IOException e )
* // {
* // Suppressed. If resource1 != null, an exception has already been thrown in the try block we need to
* // propagate instead of this one.
* // }
* // finally
* // {
* // try
* // {
* // if ( resource2 != null )
* // {
* // resource2.close();
* // }
* // }
* // catch ( IOException e )
* // {
* // Suppressed. If resource2 != null, an exception has already been thrown in the try block we need to
* // propagate instead of this one.
* // }
* // }
* }
*
*
*
* @param reader The reader to close or {@code null}.
*/
public static void close( @Nullable Reader reader )
{
try
{
if ( reader != null )
{
reader.close();
}
}
catch ( IOException ex )
{
// Suppressed
}
}
/**
* Closes a {@code Writer} suppressing any {@code IOException}.
*
* Note:
The usecase justifying this method is a shortcoming of the Java language up to but not including
* Java 7. For any code targeting Java 7 or later use of this method is highly discouraged and the
* {@code try-with-resources} statement should be used instead. Care must be taken to not use this method in a way
* {@code IOException}s get suppressed incorrectly.
* You must close all resources in use inside the {@code try} block to not suppress exceptions in the
* {@code finally} block incorrectly by using this method.
*
*
* Example:
*
* // Introduce variables for the resources and initialize them to null. This cannot throw an exception.
* Closeable resource1 = null;
* Closeable resource2 = null;
* try
* {
* // Obtain a resource object and assign it to variable resource1. This may throw an exception.
* // If successful, resource1 != null.
* resource1 = ...
*
* // Obtain a resource object and assign it to variable resource2. This may throw an exception.
* // If successful, resource2 != null. Not reached if an exception has been thrown above.
* resource2 = ...
*
* // Perform operations on the resources. This may throw an exception. Not reached if an exception has been
* // thrown above. Note: Treat the variables resource1 and resource2 the same way as if they would have been
* // declared with the final modifier - that is - do NOT write anyting like resource1 = something else or
* // resource2 = something else here.
* resource1 ...
* resource2 ...
*
* // Finally, close the resources and set the variables to null indicating successful completion.
* // This may throw an exception. Not reached if an exception has been thrown above.
* resource1.close();
* resource1 = null;
* // This may throw an exception. Not reached if an exception has been thrown above.
* resource2.close();
* resource2 = null;
*
* // All resources are closed at this point and all operations (up to here) completed successfully without
* // throwing an exception we would need to handle (by letting it propagate or by catching and handling it).
* }
* finally
* {
* // Cleanup any resource not closed in the try block due to an exception having been thrown and suppress any
* // exception this may produce to not stop the exception from the try block to be propagated. If the try
* // block completed successfully, all variables will have been set to null there and this will not do
* // anything. This is just to cleanup properly in case of an exception.
*
* IOUtil.close( resource1 );
* IOUtil.close( resource2 );
*
* // Without that utility method you would need to write the following:
* //
* // try
* // {
* // if ( resource1 != null )
* // {
* // resource1.close();
* // }
* // }
* // catch( IOException e )
* // {
* // Suppressed. If resource1 != null, an exception has already been thrown in the try block we need to
* // propagate instead of this one.
* // }
* // finally
* // {
* // try
* // {
* // if ( resource2 != null )
* // {
* // resource2.close();
* // }
* // }
* // catch ( IOException e )
* // {
* // Suppressed. If resource2 != null, an exception has already been thrown in the try block we need to
* // propagate instead of this one.
* // }
* // }
* }
*
*
*
* @param writer The writer to close or {@code null}.
*/
public static void close( @Nullable Writer writer )
{
try
{
if ( writer != null )
{
writer.close();
}
}
catch ( IOException ex )
{
// Suppressed
}
}
}
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