    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 1085209 2011-03-25 00:08:04Z 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         *
    094         * @exception IOException
    095         *                   thrown on any failure to read from the sever.
    096         */
    097        public void readServerList(InputStream stream, String encoding)
    098        throws IOException
    099        {
    100            this.entries = new LinkedList<String>();
    101            readStream(stream, encoding);
    102            this.parser.preParse(this.entries);
    103            resetIterator();
    104        }
    105
    106        /**
    107         * Internal method for reading the input into the <code>entries</code> list.
    108         * After this method has completed, <code>entries</code> will contain a
    109         * collection of entries (as defined by
    110         * <code>FTPFileEntryParser.readNextEntry()</code>), but this may contain
    111         * various non-entry preliminary lines from the server output, duplicates,
    112         * and other data that will not be part of the final listing.
    113         *
    114         * @param stream The socket stream on which the input will be read.
    115         * @param encoding The encoding to use.
    116         *
    117         * @exception IOException
    118         *                   thrown on any failure to read the stream
    119         */
    120        private void readStream(InputStream stream, String encoding) throws IOException
    121        {
    122            BufferedReader reader;
    123            if (encoding == null)
    124            {
    125                reader = new BufferedReader(new InputStreamReader(stream));
    126            }
    127            else
    128            {
    129                reader = new BufferedReader(new InputStreamReader(stream, encoding));
    130            }
    131
    132            String line = this.parser.readNextEntry(reader);
    133
    134            while (line != null)
    135            {
    136                this.entries.add(line);
    137                line = this.parser.readNextEntry(reader);
    138            }
    139            reader.close();
    140        }
    141
    142        /**
    143         * Returns an array of at most <code>quantityRequested</code> FTPFile
    144         * objects starting at this object's internal iterator's current position.
    145         * If fewer than <code>quantityRequested</code> such
    146         * elements are available, the returned array will have a length equal
    147         * to the number of entries at and after after the current position.
    148         * If no such entries are found, this array will have a length of 0.
    149         *
    150         * After this method is called this object's internal iterator is advanced
    151         * by a number of positions equal to the size of the array returned.
    152         *
    153         * @param quantityRequested
    154         * the maximum number of entries we want to get.
    155         *
    156         * @return an array of at most <code>quantityRequested</code> FTPFile
    157         * objects starting at the current position of this iterator within its
    158         * list and at least the number of elements which  exist in the list at
    159         * and after its current position.
    160         * <p><b>
    161         * NOTE:</b> This array may contain null members if any of the
    162         * individual file listings failed to parse.  The caller should
    163         * check each entry for null before referencing it.
    164         */
    165        public FTPFile[] getNext(int quantityRequested) {
    166            List<FTPFile> tmpResults = new LinkedList<FTPFile>();
    167            int count = quantityRequested;
    168            while (count > 0 && this._internalIterator.hasNext()) {
    169                String entry = this._internalIterator.next();
    170                FTPFile temp = this.parser.parseFTPEntry(entry);
    171                tmpResults.add(temp);
    172                count--;
    173            }
    174            return tmpResults.toArray(new FTPFile[tmpResults.size()]);
    175
    176        }
    177
    178        /**
    179         * Returns an array of at most <code>quantityRequested</code> FTPFile
    180         * objects starting at this object's internal iterator's current position,
    181         * and working back toward the beginning.
    182         *
    183         * If fewer than <code>quantityRequested</code> such
    184         * elements are available, the returned array will have a length equal
    185         * to the number of entries at and after after the current position.
    186         * If no such entries are found, this array will have a length of 0.
    187         *
    188         * After this method is called this object's internal iterator is moved
    189         * back by a number of positions equal to the size of the array returned.
    190         *
    191         * @param quantityRequested
    192         * the maximum number of entries we want to get.
    193         *
    194         * @return an array of at most <code>quantityRequested</code> FTPFile
    195         * objects starting at the current position of this iterator within its
    196         * list and at least the number of elements which  exist in the list at
    197         * and after its current position.  This array will be in the same order
    198         * as the underlying list (not reversed).
    199         * <p><b>
    200         * NOTE:</b> This array may contain null members if any of the
    201         * individual file listings failed to parse.  The caller should
    202         * check each entry for null before referencing it.
    203         */
    204        public FTPFile[] getPrevious(int quantityRequested) {
    205            List<FTPFile> tmpResults = new LinkedList<FTPFile>();
    206            int count = quantityRequested;
    207            while (count > 0 && this._internalIterator.hasPrevious()) {
    208                String entry = this._internalIterator.previous();
    209                FTPFile temp = this.parser.parseFTPEntry(entry);
    210                tmpResults.add(0,temp);
    211                count--;
    212            }
    213            return tmpResults.toArray(new FTPFile[tmpResults.size()]);
    214        }
    215
    216        /**
    217         * Returns an array of FTPFile objects containing the whole list of
    218         * files returned by the server as read by this object's parser.
    219         *
    220         * @return an array of FTPFile objects containing the whole list of
    221         *         files returned by the server as read by this object's parser.
    222         * None of the entries will be null
    223         * @exception IOException
    224         */
    225        public FTPFile[] getFiles()
    226        throws IOException
    227        {
    228            return getFiles(FTPFileFilters.NON_NULL);
    229        }
    230
    231        /**
    232         * Returns an array of FTPFile objects containing the whole list of
    233         * files returned by the server as read by this object's parser.
    234         * The files are filtered before being added to the array.
    235         *
    236         * @param filter FTPFileFilter, must not be <code>null</code>.
    237         *
    238         * @return an array of FTPFile objects containing the whole list of
    239         *         files returned by the server as read by this object's parser.
    240         * <p><b>
    241         * NOTE:</b> This array may contain null members if any of the
    242         * individual file listings failed to parse.  The caller should
    243         * check each entry for null before referencing it, or use the
    244         * a filter such as {@link FTPFileFilters#NON_NULL} which does not
    245         * allow null entries.
    246         * @since 2.2
    247         * @exception IOException
    248         */
    249        public FTPFile[] getFiles(FTPFileFilter filter)
    250        throws IOException
    251        {
    252            List<FTPFile> tmpResults = new ArrayList<FTPFile>();
    253            Iterator<String> iter = this.entries.iterator();
    254            while (iter.hasNext()) {
    255                String entry = iter.next();
    256                FTPFile temp = this.parser.parseFTPEntry(entry);
    257                if (filter.accept(temp)){
    258                    tmpResults.add(temp);
    259                }
    260            }
    261            return tmpResults.toArray(new FTPFile[tmpResults.size()]);
    262
    263        }
    264
    265        /**
    266         * convenience method to allow clients to know whether this object's
    267         * internal iterator's current position is at the end of the list.
    268         *
    269         * @return true if internal iterator is not at end of list, false
    270         * otherwise.
    271         */
    272        public boolean hasNext() {
    273            return _internalIterator.hasNext();
    274        }
    275
    276        /**
    277         * convenience method to allow clients to know whether this object's
    278         * internal iterator's current position is at the beginning of the list.
    279         *
    280         * @return true if internal iterator is not at beginning of list, false
    281         * otherwise.
    282         */
    283        public boolean hasPrevious() {
    284            return _internalIterator.hasPrevious();
    285        }
    286
    287        /**
    288         * resets this object's internal iterator to the beginning of the list.
    289         */
    290        public void resetIterator() {
    291            this._internalIterator = this.entries.listIterator();
    292        }
    293
    294        // DEPRECATED METHODS - for API compatibility only - DO NOT USE
    295
    296        /**
    297         * Do not use.
    298         * @deprecated use {@link #readServerList(InputStream, String)} instead
    299        */
    300        @Deprecated
    301        public void readServerList(InputStream stream)
    302        throws IOException
    303        {
    304            readServerList(stream, null);
    305        }
    306
    307    }