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.core.io; import java.io.File; import java.io.FileNotFoundException; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.net.URI; import java.net.URL; import java.nio.channels.FileChannel; import java.nio.channels.ReadableByteChannel; import java.nio.channels.WritableByteChannel; import java.nio.file.FileSystem; import java.nio.file.Files; import java.nio.file.NoSuchFileException; import java.nio.file.Path; import java.nio.file.StandardOpenOption; import org.springframework.lang.Nullable; import org.springframework.util.Assert; import org.springframework.util.StringUtils; /** * {@link Resource} implementation for {@code java.io.File} and * {@code java.nio.file.Path} handles with a file system target. * Supports resolution as a {@code File} and also as a {@code URL}. * Implements the extended {@link WritableResource} interface. * * <p>Note: As of Spring Framework 5.0, this {@link Resource} implementation uses * NIO.2 API for read/write interactions. As of 5.1, it may be constructed with a * {@link java.nio.file.Path} handle in which case it will perform all file system * interactions via NIO.2, only resorting to {@link File} on {@link #getFile()}. * * @author Juergen Hoeller * @since 28.12.2003 * @see #FileSystemResource(File) * @see #FileSystemResource(Path) * @see java.io.File * @see java.nio.file.Files */ public class FileSystemResource extends AbstractResource implements WritableResource { private final String path; @Nullable private final File file; private final Path filePath; /** * Create a new {@code FileSystemResource} from a file path. * <p>Note: When building relative resources via {@link #createRelative}, * it makes a difference whether the specified resource base path here * ends with a slash or not. In the case of "C:/dir1/", relative paths * will be built underneath that root: e.g. relative path "dir2" -> * "C:/dir1/dir2". In the case of "C:/dir1", relative paths will apply * at the same directory level: relative path "dir2" -> "C:/dir2". * @param path a file path * @see #FileSystemResource(Path) */ public FileSystemResource(String path) { Assert.notNull(path, "Path must not be null"); this.path = StringUtils.cleanPath(path); this.file = new File(path); this.filePath = this.file.toPath(); } /** * Create a new {@code FileSystemResource} from a {@link File} handle. * <p>Note: When building relative resources via {@link #createRelative}, * the relative path will apply <i>at the same directory level</i>: * e.g. new File("C:/dir1"), relative path "dir2" -> "C:/dir2"! * If you prefer to have relative paths built underneath the given root directory, * use the {@link #FileSystemResource(String) constructor with a file path} * to append a trailing slash to the root path: "C:/dir1/", which indicates * this directory as root for all relative paths. * @param file a File handle * @see #FileSystemResource(Path) * @see #getFile() */ public FileSystemResource(File file) { Assert.notNull(file, "File must not be null"); this.path = StringUtils.cleanPath(file.getPath()); this.file = file; this.filePath = file.toPath(); } /** * Create a new {@code FileSystemResource} from a {@link Path} handle, * performing all file system interactions via NIO.2 instead of {@link File}. * <p>In contrast to {@link PathResource}, this variant strictly follows the * general {@link FileSystemResource} conventions, in particular in terms of * path cleaning and {@link #createRelative(String)} handling. * @param filePath a Path handle to a file * @since 5.1 * @see #FileSystemResource(File) */ public FileSystemResource(Path filePath) { Assert.notNull(filePath, "Path must not be null"); this.path = StringUtils.cleanPath(filePath.toString()); this.file = null; this.filePath = filePath; } /** * Create a new {@code FileSystemResource} from a {@link FileSystem} handle, * locating the specified path. * <p>This is an alternative to {@link #FileSystemResource(String)}, * performing all file system interactions via NIO.2 instead of {@link File}. * @param fileSystem the FileSystem to locate the path within * @param path a file path * @since 5.1.1 * @see #FileSystemResource(File) */ public FileSystemResource(FileSystem fileSystem, String path) { Assert.notNull(fileSystem, "FileSystem must not be null"); Assert.notNull(path, "Path must not be null"); this.path = StringUtils.cleanPath(path); this.file = null; this.filePath = fileSystem.getPath(this.path).normalize(); } /** * Return the file path for this resource. */ public final String getPath() { return this.path; } /** * This implementation returns whether the underlying file exists. * @see java.io.File#exists() */ @Override public boolean exists() { return (this.file != null ? this.file.exists() : Files.exists(this.filePath)); } /** * This implementation checks whether the underlying file is marked as readable * (and corresponds to an actual file with content, not to a directory). * @see java.io.File#canRead() * @see java.io.File#isDirectory() */ @Override public boolean isReadable() { return (this.file != null ? this.file.canRead() && !this.file.isDirectory() : Files.isReadable(this.filePath) && !Files.isDirectory(this.filePath)); } /** * This implementation opens a NIO file stream for the underlying file. * @see java.io.FileInputStream */ @Override public InputStream getInputStream() throws IOException { try { return Files.newInputStream(this.filePath); } catch (NoSuchFileException ex) { throw new FileNotFoundException(ex.getMessage()); } } /** * This implementation checks whether the underlying file is marked as writable * (and corresponds to an actual file with content, not to a directory). * @see java.io.File#canWrite() * @see java.io.File#isDirectory() */ @Override public boolean isWritable() { return (this.file != null ? this.file.canWrite() && !this.file.isDirectory() : Files.isWritable(this.filePath) && !Files.isDirectory(this.filePath)); } /** * This implementation opens a FileOutputStream for the underlying file. * @see java.io.FileOutputStream */ @Override public OutputStream getOutputStream() throws IOException { return Files.newOutputStream(this.filePath); } /** * This implementation returns a URL for the underlying file. * @see java.io.File#toURI() */ @Override public URL getURL() throws IOException { return (this.file != null ? this.file.toURI().toURL() : this.filePath.toUri().toURL()); } /** * This implementation returns a URI for the underlying file. * @see java.io.File#toURI() */ @Override public URI getURI() throws IOException { return (this.file != null ? this.file.toURI() : this.filePath.toUri()); } /** * This implementation always indicates a file. */ @Override public boolean isFile() { return true; } /** * This implementation returns the underlying File reference. */ @Override public File getFile() { return (this.file != null ? this.file : this.filePath.toFile()); } /** * This implementation opens a FileChannel for the underlying file. * @see java.nio.channels.FileChannel */ @Override public ReadableByteChannel readableChannel() throws IOException { try { return FileChannel.open(this.filePath, StandardOpenOption.READ); } catch (NoSuchFileException ex) { throw new FileNotFoundException(ex.getMessage()); } } /** * This implementation opens a FileChannel for the underlying file. * @see java.nio.channels.FileChannel */ @Override public WritableByteChannel writableChannel() throws IOException { return FileChannel.open(this.filePath, StandardOpenOption.WRITE); } /** * This implementation returns the underlying File/Path length. */ @Override public long contentLength() throws IOException { if (this.file != null) { long length = this.file.length(); if (length == 0L && !this.file.exists()) { throw new FileNotFoundException(getDescription() + " cannot be resolved in the file system for checking its content length"); } return length; } else { try { return Files.size(this.filePath); } catch (NoSuchFileException ex) { throw new FileNotFoundException(ex.getMessage()); } } } /** * This implementation returns the underlying File/Path last-modified time. */ @Override public long lastModified() throws IOException { if (this.file != null) { return super.lastModified(); } else { try { return Files.getLastModifiedTime(this.filePath).toMillis(); } catch (NoSuchFileException ex) { throw new FileNotFoundException(ex.getMessage()); } } } /** * This implementation creates a FileSystemResource, applying the given path * relative to the path of the underlying file of this resource descriptor. * @see org.springframework.util.StringUtils#applyRelativePath(String, String) */ @Override public Resource createRelative(String relativePath) { String pathToUse = StringUtils.applyRelativePath(this.path, relativePath); return (this.file != null ? new FileSystemResource(pathToUse) : new FileSystemResource(this.filePath.getFileSystem(), pathToUse)); } /** * This implementation returns the name of the file. * @see java.io.File#getName() */ @Override public String getFilename() { return (this.file != null ? this.file.getName() : this.filePath.getFileName().toString()); } /** * This implementation returns a description that includes the absolute * path of the file. * @see java.io.File#getAbsolutePath() */ @Override public String getDescription() { return "file [" + (this.file != null ? this.file.getAbsolutePath() : this.filePath.toAbsolutePath()) + "]"; } /** * This implementation compares the underlying File references. */ @Override public boolean equals(@Nullable Object other) { return (this == other || (other instanceof FileSystemResource && this.path.equals(((FileSystemResource) other).path))); } /** * This implementation returns the hash code of the underlying File reference. */ @Override public int hashCode() { return this.path.hashCode(); } }