FTPListParseEngine.java
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.net.ftp;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.LinkedList;
import java.util.List;
import java.util.ListIterator;
import java.util.stream.Collectors;
import org.apache.commons.net.util.Charsets;
/**
* This class handles the entire process of parsing a listing of file entries from the server.
* <p>
* This object defines a two-part parsing mechanism.
* <p>
* The first part consists of reading the raw input into an internal list of strings. Every item in this list corresponds to an actual file. All extraneous
* matter emitted by the server will have been removed by the end of this phase. This is accomplished in conjunction with the FTPFileEntryParser associated with
* this engine, by calling its methods <code>readNextEntry()</code> - which handles the issue of what delimits one entry from another, usually but not always a
* line feed and <code>preParse()</code> - which handles removal of extraneous matter such as the preliminary lines of a listing, removal of duplicates on
* versioning systems, etc.
* <p>
* The second part is composed of the actual parsing, again in conjunction with the particular parser used by this engine. This is controlled by an iterator
* over the internal list of strings. This may be done either in block mode, by calling the <code>getNext()</code> and <code>getPrevious()</code> methods to
* provide "paged" output of less than the whole list at one time, or by calling the <code>getFiles()</code> method to return the entire list.
* <p>
* Examples:
* <p>
* Paged access:
*
* <pre>
* FTPClient f = FTPClient();
* f.connect(server);
* f.login(user, password);
* FTPListParseEngine engine = f.initiateListParsing(directory);
*
* while (engine.hasNext()) {
* FTPFile[] files = engine.getNext(25); // "page size" you want
* // do whatever you want with these files, display them, etc.
* // expensive FTPFile objects not created until needed.
* }
* </pre>
* <p>
* For unpaged access, simply use FTPClient.listFiles(). That method uses this class transparently.
*/
public class FTPListParseEngine {
/**
* An empty immutable {@code FTPFile} array.
*/
private static final FTPFile[] EMPTY_FTP_FILE_ARRAY = {};
private List<String> entries = new LinkedList<>();
private ListIterator<String> internalIterator = entries.listIterator();
private final FTPFileEntryParser parser;
// Should invalid files (parse failures) be allowed?
private final boolean saveUnparseableEntries;
public FTPListParseEngine(final FTPFileEntryParser parser) {
this(parser, null);
}
/**
* Intended for use by FTPClient only
*
* @since 3.4
*/
FTPListParseEngine(final FTPFileEntryParser parser, final FTPClientConfig configuration) {
this.parser = parser;
if (configuration != null) {
this.saveUnparseableEntries = configuration.getUnparseableEntries();
} else {
this.saveUnparseableEntries = false;
}
}
/**
* Returns a list of FTPFile objects containing the whole list of files returned by the server as read by this object's parser. The files are filtered
* before being added to the array.
*
* @param filter FTPFileFilter, must not be <code>null</code>.
*
* @return a list of FTPFile objects containing the whole list of files returned by the server as read by this object's parser.
* <p>
* <b> NOTE:</b> This array may contain null members if any of the individual file listings failed to parse. The caller should check each entry for
* null before referencing it, or use a filter such as {@link FTPFileFilters#NON_NULL} which does not allow null entries.
* @since 3.9.0
*/
public List<FTPFile> getFileList(final FTPFileFilter filter) {
return entries.stream().map(e -> {
final FTPFile file = parser.parseFTPEntry(e);
return file == null && saveUnparseableEntries ? new FTPFile(e) : file;
}).filter(filter::accept).collect(Collectors.toList());
}
/**
* Returns an array of FTPFile objects containing the whole list of files returned by the server as read by this object's parser.
*
* @return an array of FTPFile objects containing the whole list of files returned by the server as read by this object's parser. None of the entries will
* be null
* @throws IOException - not ever thrown, may be removed in a later release
*/
public FTPFile[] getFiles() throws IOException // TODO remove; not actually thrown
{
return getFiles(FTPFileFilters.NON_NULL);
}
/**
* Returns an array of FTPFile objects containing the whole list of files returned by the server as read by this object's parser. The files are filtered
* before being added to the array.
*
* @param filter FTPFileFilter, must not be <code>null</code>.
*
* @return an array of FTPFile objects containing the whole list of files returned by the server as read by this object's parser.
* <p>
* <b> NOTE:</b> This array may contain null members if any of the individual file listings failed to parse. The caller should check each entry for
* null before referencing it, or use a filter such as {@link FTPFileFilters#NON_NULL} which does not allow null entries.
* @since 2.2
* @throws IOException - not ever thrown, may be removed in a later release
*/
public FTPFile[] getFiles(final FTPFileFilter filter) throws IOException // TODO remove; not actually thrown
{
return getFileList(filter).toArray(EMPTY_FTP_FILE_ARRAY);
}
/**
* Returns an array of at most <code>quantityRequested</code> FTPFile objects starting at this object's internal iterator's current position. If fewer than
* <code>quantityRequested</code> such elements are available, the returned array will have a length equal to the number of entries at and after the
* current position. If no such entries are found, this array will have a length of 0.
*
* After this method is called this object's internal iterator is advanced by a number of positions equal to the size of the array returned.
*
* @param quantityRequested the maximum number of entries we want to get.
*
* @return an array of at most <code>quantityRequested</code> FTPFile objects starting at the current position of this iterator within its list and at least
* the number of elements which exist in the list at and after its current position.
* <p>
* <b> NOTE:</b> This array may contain null members if any of the individual file listings failed to parse. The caller should check each entry for
* null before referencing it.
*/
public FTPFile[] getNext(final int quantityRequested) {
final List<FTPFile> tmpResults = new LinkedList<>();
int count = quantityRequested;
while (count > 0 && this.internalIterator.hasNext()) {
final String entry = this.internalIterator.next();
FTPFile temp = this.parser.parseFTPEntry(entry);
if (temp == null && saveUnparseableEntries) {
temp = new FTPFile(entry);
}
tmpResults.add(temp);
count--;
}
return tmpResults.toArray(EMPTY_FTP_FILE_ARRAY);
}
/**
* Returns an array of at most <code>quantityRequested</code> FTPFile objects starting at this object's internal iterator's current position, and working
* back toward the beginning.
*
* If fewer than <code>quantityRequested</code> such elements are available, the returned array will have a length equal to the number of entries at and
* after the current position. If no such entries are found, this array will have a length of 0.
*
* After this method is called this object's internal iterator is moved back by a number of positions equal to the size of the array returned.
*
* @param quantityRequested the maximum number of entries we want to get.
*
* @return an array of at most <code>quantityRequested</code> FTPFile objects starting at the current position of this iterator within its list and at least
* the number of elements which exist in the list at and after its current position. This array will be in the same order as the underlying list
* (not reversed).
* <p>
* <b> NOTE:</b> This array may contain null members if any of the individual file listings failed to parse. The caller should check each entry for
* null before referencing it.
*/
public FTPFile[] getPrevious(final int quantityRequested) {
final List<FTPFile> tmpResults = new LinkedList<>();
int count = quantityRequested;
while (count > 0 && this.internalIterator.hasPrevious()) {
final String entry = this.internalIterator.previous();
FTPFile temp = this.parser.parseFTPEntry(entry);
if (temp == null && saveUnparseableEntries) {
temp = new FTPFile(entry);
}
tmpResults.add(0, temp);
count--;
}
return tmpResults.toArray(EMPTY_FTP_FILE_ARRAY);
}
/**
* convenience method to allow clients to know whether this object's internal iterator's current position is at the end of the list.
*
* @return true if internal iterator is not at end of list, false otherwise.
*/
public boolean hasNext() {
return internalIterator.hasNext();
}
/**
* convenience method to allow clients to know whether this object's internal iterator's current position is at the beginning of the list.
*
* @return true if internal iterator is not at beginning of list, false otherwise.
*/
public boolean hasPrevious() {
return internalIterator.hasPrevious();
}
/**
* Internal method for reading (and closing) the input into the <code>entries</code> list. After this method has completed, <code>entries</code> will
* contain a collection of entries (as defined by <code>FTPFileEntryParser.readNextEntry()</code>), but this may contain various non-entry preliminary lines
* from the server output, duplicates, and other data that will not be part of the final listing.
*
* @param inputStream The socket stream on which the input will be read.
* @param charsetName The encoding to use.
*
* @throws IOException thrown on any failure to read the stream
*/
private void read(final InputStream inputStream, final String charsetName) throws IOException {
try (final BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream, Charsets.toCharset(charsetName)))) {
String line = this.parser.readNextEntry(reader);
while (line != null) {
this.entries.add(line);
line = this.parser.readNextEntry(reader);
}
}
}
/**
* Do not use.
*
* @param inputStream the stream from which to read
* @throws IOException on error
* @deprecated use {@link #readServerList(InputStream, String)} instead
*/
@Deprecated
public void readServerList(final InputStream inputStream) throws IOException {
readServerList(inputStream, null);
}
/**
* Reads (and closes) the initial reading and preparsing of the list returned by the server. After this method has completed, this object will contain a
* list of unparsed entries (Strings) each referring to a unique file on the server.
*
* @param inputStream input stream provided by the server socket.
* @param charsetName the encoding to be used for reading the stream
*
* @throws IOException thrown on any failure to read from the sever.
*/
public void readServerList(final InputStream inputStream, final String charsetName) throws IOException {
this.entries = new LinkedList<>();
read(inputStream, charsetName);
this.parser.preParse(this.entries);
resetIterator();
}
// DEPRECATED METHODS - for API compatibility only - DO NOT USE
/**
* resets this object's internal iterator to the beginning of the list.
*/
public void resetIterator() {
this.internalIterator = this.entries.listIterator();
}
}