    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    }