001// Copyright (C) 2002 by Jason Hunter <jhunter_AT_acm_DOT_org>. 002// All rights reserved. Use of this class is limited. 003// Please see the LICENSE for more information. 004 005package com.oreilly.servlet.multipart; 006 007import java.io.*; 008 009/** 010 * Implements a renaming policy that adds increasing integers to the body of 011 * any file that collides. For example, if foo.gif is being uploaded and a 012 * file by the same name already exists, this logic will rename the upload 013 * foo1.gif. A second upload by the same name would be foo2.gif. 014 * Note that for safety the rename() method creates a zero-length file with 015 * the chosen name to act as a marker that the name is taken even before the 016 * upload starts writing the bytes. 017 * 018 * @author Jason Hunter 019 * @version 1.1, 2002/11/05, making thread safe with createNewFile() 020 * @version 1.0, 2002/04/30, initial revision, thanks to Yoonjung Lee 021 * for this idea 022 */ 023public class DefaultFileRenamePolicy implements FileRenamePolicy { 024 025 // This method does not need to be synchronized because createNewFile() 026 // is atomic and used here to mark when a file name is chosen 027 public File rename(File f) { 028 if (createNewFile(f)) { 029 return f; 030 } 031 String name = f.getName(); 032 String body = null; 033 String ext = null; 034 035 int dot = name.lastIndexOf("."); 036 if (dot != -1) { 037 body = name.substring(0, dot); 038 ext = name.substring(dot); // includes "." 039 } 040 else { 041 body = name; 042 ext = ""; 043 } 044 045 // Increase the count until an empty spot is found. 046 // Max out at 9999 to avoid an infinite loop caused by a persistent 047 // IOException, like when the destination dir becomes non-writable. 048 // We don't pass the exception up because our job is just to rename, 049 // and the caller will hit any IOException in normal processing. 050 int count = 0; 051 while (!createNewFile(f) && count < 9999) { 052 count++; 053 String newName = body + count + ext; 054 f = new File(f.getParent(), newName); 055 } 056 057 return f; 058 } 059 060 private boolean createNewFile(File f) { 061 try { 062 return f.createNewFile(); 063 } 064 catch (IOException ignored) { 065 return false; 066 } 067 } 068}