Java tutorial
/* * Copyright 2002-2018 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.File; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.io.Reader; import java.io.StringWriter; import java.io.Writer; import java.nio.file.Files; import org.springframework.lang.Nullable; /** * Simple utility methods for file and stream copying. All copy methods use a block size * of 4096 bytes, and close all affected streams when done. A variation of the copy * methods from this class that leave streams open can be found in {@link StreamUtils}. * * <p>Mainly for use within the framework, but also useful for application code. * * @author Juergen Hoeller * @since 06.10.2003 * @see StreamUtils * @see FileSystemUtils */ public abstract class FileCopyUtils { /** * The default buffer size used when copying bytes. */ public static final int BUFFER_SIZE = StreamUtils.BUFFER_SIZE; //--------------------------------------------------------------------- // Copy methods for java.io.File //--------------------------------------------------------------------- /** * Copy the contents of the given input File to the given output File. * @param in the file to copy from * @param out the file to copy to * @return the number of bytes copied * @throws IOException in case of I/O errors */ public static int copy(File in, File out) throws IOException { Assert.notNull(in, "No input File specified"); Assert.notNull(out, "No output File specified"); return copy(Files.newInputStream(in.toPath()), Files.newOutputStream(out.toPath())); } /** * Copy the contents of the given byte array to the given output File. * @param in the byte array to copy from * @param out the file to copy to * @throws IOException in case of I/O errors */ public static void copy(byte[] in, File out) throws IOException { Assert.notNull(in, "No input byte array specified"); Assert.notNull(out, "No output File specified"); copy(new ByteArrayInputStream(in), Files.newOutputStream(out.toPath())); } /** * Copy the contents of the given input File into a new byte array. * @param in the file to copy from * @return the new byte array that has been copied to * @throws IOException in case of I/O errors */ public static byte[] copyToByteArray(File in) throws IOException { Assert.notNull(in, "No input File specified"); return copyToByteArray(Files.newInputStream(in.toPath())); } //--------------------------------------------------------------------- // Copy methods for java.io.InputStream / java.io.OutputStream //--------------------------------------------------------------------- /** * Copy the contents of the given InputStream to the given OutputStream. * Closes both streams when done. * @param in the stream to copy from * @param out the stream 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"); try { return StreamUtils.copy(in, out); } finally { try { in.close(); } catch (IOException ex) { } try { out.close(); } catch (IOException ex) { } } } /** * Copy the contents of the given byte array to the given OutputStream. * Closes the stream 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"); try { out.write(in); } finally { try { out.close(); } catch (IOException ex) { } } } /** * Copy the contents of the given InputStream into a new byte array. * Closes the stream 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(@Nullable InputStream in) throws IOException { if (in == null) { return new byte[0]; } ByteArrayOutputStream out = new ByteArrayOutputStream(BUFFER_SIZE); copy(in, out); return out.toByteArray(); } //--------------------------------------------------------------------- // Copy methods for java.io.Reader / java.io.Writer //--------------------------------------------------------------------- /** * Copy the contents of the given Reader to the given Writer. * Closes both when done. * @param in the Reader to copy from * @param out the Writer to copy to * @return the number of characters copied * @throws IOException in case of I/O errors */ public static int copy(Reader in, Writer out) throws IOException { Assert.notNull(in, "No Reader specified"); Assert.notNull(out, "No Writer specified"); try { int byteCount = 0; char[] buffer = new char[BUFFER_SIZE]; int bytesRead = -1; while ((bytesRead = in.read(buffer)) != -1) { out.write(buffer, 0, bytesRead); byteCount += bytesRead; } out.flush(); return byteCount; } finally { try { in.close(); } catch (IOException ex) { } try { out.close(); } catch (IOException ex) { } } } /** * Copy the contents of the given String to the given output Writer. * Closes the writer when done. * @param in the String to copy from * @param out the Writer to copy to * @throws IOException in case of I/O errors */ public static void copy(String in, Writer out) throws IOException { Assert.notNull(in, "No input String specified"); Assert.notNull(out, "No Writer specified"); try { out.write(in); } finally { try { out.close(); } catch (IOException ex) { } } } /** * Copy the contents of the given Reader into a String. * Closes the reader when done. * @param in the reader 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(@Nullable Reader in) throws IOException { if (in == null) { return ""; } StringWriter out = new StringWriter(); copy(in, out); return out.toString(); } }