/*
* Copyright (c) 2007, 2011, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*
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*/
package java.nio.file.spi;
import java.nio.file.Path;
import java.io.IOException;
/**
* A file type detector for probing a file to guess its file type.
*
* <p> A file type detector is a concrete implementation of this class, has a
* zero-argument constructor, and implements the abstract methods specified
* below.
*
* <p> The means by which a file type detector determines the file type is
* highly implementation specific. A simple implementation might examine the
* <em>file extension</em> (a convention used in some platforms) and map it to
* a file type. In other cases, the file type may be stored as a file <a
* href="../attribute/package-summary.html"> attribute</a> or the bytes in a
* file may be examined to guess its file type.
*
* @see java.nio.file.Files#probeContentType(Path)
*
* @since 1.7
*/
public abstract class FileTypeDetector {
private static Void checkPermission() {
SecurityManager sm = System.getSecurityManager();
if (sm != null)
sm.checkPermission(new RuntimePermission("fileTypeDetector"));
return null;
}
private FileTypeDetector(Void ignore) { }
/**
* Initializes a new instance of this class.
*
* @throws SecurityException
* If a security manager has been installed and it denies
* {@link RuntimePermission}<tt>("fileTypeDetector")</tt>
*/
protected FileTypeDetector() {
this(checkPermission());
}
/**
* Probes the given file to guess its content type.
*
* <p> The means by which this method determines the file type is highly
* implementation specific. It may simply examine the file name, it may use
* a file <a href="../attribute/package-summary.html">attribute</a>,
* or it may examines bytes in the file.
*
* <p> The probe result is the string form of the value of a
* Multipurpose Internet Mail Extension (MIME) content type as
* defined by <a href="http://www.ietf.org/rfc/rfc2045.txt"><i>RFC 2045:
* Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet
* Message Bodies</i></a>. The string must be parsable according to the
* grammar in the RFC 2045.
*
* @param path
* the path to the file to probe
*
* @return The content type or {@code null} if the file type is not
* recognized
*
* @throws IOException
* An I/O error occurs
* @throws SecurityException
* If the implementation requires to access the file, and a
* security manager is installed, and it denies an unspecified
* permission required by a file system provider implementation.
* If the file reference is associated with the default file system
* provider then the {@link SecurityManager#checkRead(String)} method
* is invoked to check read access to the file.
*
* @see java.nio.file.Files#probeContentType
*/
public abstract String probeContentType(Path path)
throws IOException;
}