001 /*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017
018 package org.apache.commons.net.ftp;
019
020 import java.io.BufferedReader;
021 import java.io.IOException;
022 import java.io.InputStream;
023 import java.io.InputStreamReader;
024 import java.util.ArrayList;
025 import java.util.Iterator;
026 import java.util.LinkedList;
027 import java.util.List;
028 import java.util.ListIterator;
029
030
031 /**
032 * This class handles the entire process of parsing a listing of
033 * file entries from the server.
034 * <p>
035 * This object defines a two-part parsing mechanism.
036 * <p>
037 * The first part is comprised of reading the raw input into an internal
038 * list of strings. Every item in this list corresponds to an actual
039 * file. All extraneous matter emitted by the server will have been
040 * removed by the end of this phase. This is accomplished in conjunction
041 * with the FTPFileEntryParser associated with this engine, by calling
042 * its methods <code>readNextEntry()</code> - which handles the issue of
043 * what delimits one entry from another, usually but not always a line
044 * feed and <code>preParse()</code> - which handles removal of
045 * extraneous matter such as the preliminary lines of a listing, removal
046 * of duplicates on versioning systems, etc.
047 * <p>
048 * The second part is composed of the actual parsing, again in conjunction
049 * with the particular parser used by this engine. This is controlled
050 * by an iterator over the internal list of strings. This may be done
051 * either in block mode, by calling the <code>getNext()</code> and
052 * <code>getPrevious()</code> methods to provide "paged" output of less
053 * than the whole list at one time, or by calling the
054 * <code>getFiles()</code> method to return the entire list.
055 * <p>
056 * Examples:
057 * <p>
058 * Paged access:
059 * <pre>
060 * FTPClient f=FTPClient();
061 * f.connect(server);
062 * f.login(username, password);
063 * FTPListParseEngine engine = f.initiateListParsing(directory);
064 *
065 * while (engine.hasNext()) {
066 * FTPFile[] files = engine.getNext(25); // "page size" you want
067 * //do whatever you want with these files, display them, etc.
068 * //expensive FTPFile objects not created until needed.
069 * }
070 * </pre>
071 * <p>
072 * For unpaged access, simply use FTPClient.listFiles(). That method
073 * uses this class transparently.
074 * @version $Id: FTPListParseEngine.java 1299238 2012-03-10 17:12:28Z sebb $
075 */
076 public class FTPListParseEngine {
077 private List<String> entries = new LinkedList<String>();
078 private ListIterator<String> _internalIterator = entries.listIterator();
079
080 private final FTPFileEntryParser parser;
081
082 public FTPListParseEngine(FTPFileEntryParser parser) {
083 this.parser = parser;
084 }
085
086 /**
087 * handle the initial reading and preparsing of the list returned by
088 * the server. After this method has completed, this object will contain
089 * a list of unparsed entries (Strings) each referring to a unique file
090 * on the server.
091 *
092 * @param stream input stream provided by the server socket.
093 * @param encoding the encoding to be used for reading the stream
094 *
095 * @exception IOException
096 * thrown on any failure to read from the sever.
097 */
098 public void readServerList(InputStream stream, String encoding)
099 throws IOException
100 {
101 this.entries = new LinkedList<String>();
102 readStream(stream, encoding);
103 this.parser.preParse(this.entries);
104 resetIterator();
105 }
106
107 /**
108 * Internal method for reading the input into the <code>entries</code> list.
109 * After this method has completed, <code>entries</code> will contain a
110 * collection of entries (as defined by
111 * <code>FTPFileEntryParser.readNextEntry()</code>), but this may contain
112 * various non-entry preliminary lines from the server output, duplicates,
113 * and other data that will not be part of the final listing.
114 *
115 * @param stream The socket stream on which the input will be read.
116 * @param encoding The encoding to use.
117 *
118 * @exception IOException
119 * thrown on any failure to read the stream
120 */
121 private void readStream(InputStream stream, String encoding) throws IOException
122 {
123 BufferedReader reader;
124 if (encoding == null)
125 {
126 reader = new BufferedReader(new InputStreamReader(stream));
127 }
128 else
129 {
130 reader = new BufferedReader(new InputStreamReader(stream, encoding));
131 }
132
133 String line = this.parser.readNextEntry(reader);
134
135 while (line != null)
136 {
137 this.entries.add(line);
138 line = this.parser.readNextEntry(reader);
139 }
140 reader.close();
141 }
142
143 /**
144 * Returns an array of at most <code>quantityRequested</code> FTPFile
145 * objects starting at this object's internal iterator's current position.
146 * If fewer than <code>quantityRequested</code> such
147 * elements are available, the returned array will have a length equal
148 * to the number of entries at and after after the current position.
149 * If no such entries are found, this array will have a length of 0.
150 *
151 * After this method is called this object's internal iterator is advanced
152 * by a number of positions equal to the size of the array returned.
153 *
154 * @param quantityRequested
155 * the maximum number of entries we want to get.
156 *
157 * @return an array of at most <code>quantityRequested</code> FTPFile
158 * objects starting at the current position of this iterator within its
159 * list and at least the number of elements which exist in the list at
160 * and after its current position.
161 * <p><b>
162 * NOTE:</b> This array may contain null members if any of the
163 * individual file listings failed to parse. The caller should
164 * check each entry for null before referencing it.
165 */
166 public FTPFile[] getNext(int quantityRequested) {
167 List<FTPFile> tmpResults = new LinkedList<FTPFile>();
168 int count = quantityRequested;
169 while (count > 0 && this._internalIterator.hasNext()) {
170 String entry = this._internalIterator.next();
171 FTPFile temp = this.parser.parseFTPEntry(entry);
172 tmpResults.add(temp);
173 count--;
174 }
175 return tmpResults.toArray(new FTPFile[tmpResults.size()]);
176
177 }
178
179 /**
180 * Returns an array of at most <code>quantityRequested</code> FTPFile
181 * objects starting at this object's internal iterator's current position,
182 * and working back toward the beginning.
183 *
184 * If fewer than <code>quantityRequested</code> such
185 * elements are available, the returned array will have a length equal
186 * to the number of entries at and after after the current position.
187 * If no such entries are found, this array will have a length of 0.
188 *
189 * After this method is called this object's internal iterator is moved
190 * back by a number of positions equal to the size of the array returned.
191 *
192 * @param quantityRequested
193 * the maximum number of entries we want to get.
194 *
195 * @return an array of at most <code>quantityRequested</code> FTPFile
196 * objects starting at the current position of this iterator within its
197 * list and at least the number of elements which exist in the list at
198 * and after its current position. This array will be in the same order
199 * as the underlying list (not reversed).
200 * <p><b>
201 * NOTE:</b> This array may contain null members if any of the
202 * individual file listings failed to parse. The caller should
203 * check each entry for null before referencing it.
204 */
205 public FTPFile[] getPrevious(int quantityRequested) {
206 List<FTPFile> tmpResults = new LinkedList<FTPFile>();
207 int count = quantityRequested;
208 while (count > 0 && this._internalIterator.hasPrevious()) {
209 String entry = this._internalIterator.previous();
210 FTPFile temp = this.parser.parseFTPEntry(entry);
211 tmpResults.add(0,temp);
212 count--;
213 }
214 return tmpResults.toArray(new FTPFile[tmpResults.size()]);
215 }
216
217 /**
218 * Returns an array of FTPFile objects containing the whole list of
219 * files returned by the server as read by this object's parser.
220 *
221 * @return an array of FTPFile objects containing the whole list of
222 * files returned by the server as read by this object's parser.
223 * None of the entries will be null
224 * @exception IOException - not ever thrown, may be removed in a later release
225 */
226 public FTPFile[] getFiles()
227 throws IOException // TODO remove; not actually thrown
228 {
229 return getFiles(FTPFileFilters.NON_NULL);
230 }
231
232 /**
233 * Returns an array of FTPFile objects containing the whole list of
234 * files returned by the server as read by this object's parser.
235 * The files are filtered before being added to the array.
236 *
237 * @param filter FTPFileFilter, must not be <code>null</code>.
238 *
239 * @return an array of FTPFile objects containing the whole list of
240 * files returned by the server as read by this object's parser.
241 * <p><b>
242 * NOTE:</b> This array may contain null members if any of the
243 * individual file listings failed to parse. The caller should
244 * check each entry for null before referencing it, or use the
245 * a filter such as {@link FTPFileFilters#NON_NULL} which does not
246 * allow null entries.
247 * @since 2.2
248 * @exception IOException - not ever thrown, may be removed in a later release
249 */
250 public FTPFile[] getFiles(FTPFileFilter filter)
251 throws IOException // TODO remove; not actually thrown
252 {
253 List<FTPFile> tmpResults = new ArrayList<FTPFile>();
254 Iterator<String> iter = this.entries.iterator();
255 while (iter.hasNext()) {
256 String entry = iter.next();
257 FTPFile temp = this.parser.parseFTPEntry(entry);
258 if (filter.accept(temp)){
259 tmpResults.add(temp);
260 }
261 }
262 return tmpResults.toArray(new FTPFile[tmpResults.size()]);
263
264 }
265
266 /**
267 * convenience method to allow clients to know whether this object's
268 * internal iterator's current position is at the end of the list.
269 *
270 * @return true if internal iterator is not at end of list, false
271 * otherwise.
272 */
273 public boolean hasNext() {
274 return _internalIterator.hasNext();
275 }
276
277 /**
278 * convenience method to allow clients to know whether this object's
279 * internal iterator's current position is at the beginning of the list.
280 *
281 * @return true if internal iterator is not at beginning of list, false
282 * otherwise.
283 */
284 public boolean hasPrevious() {
285 return _internalIterator.hasPrevious();
286 }
287
288 /**
289 * resets this object's internal iterator to the beginning of the list.
290 */
291 public void resetIterator() {
292 this._internalIterator = this.entries.listIterator();
293 }
294
295 // DEPRECATED METHODS - for API compatibility only - DO NOT USE
296
297 /**
298 * Do not use.
299 * @deprecated use {@link #readServerList(InputStream, String)} instead
300 */
301 @Deprecated
302 public void readServerList(InputStream stream)
303 throws IOException
304 {
305 readServerList(stream, null);
306 }
307
308 }