com.google.api.client.xml.atom.AbstractAtomFeedParser Maven / Gradle / Ivy
/*
* Copyright (c) 2010 Google Inc.
*
* Licensed 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 com.google.api.client.xml.atom;
import com.google.api.client.util.Beta;
import com.google.api.client.util.Preconditions;
import com.google.api.client.util.Types;
import com.google.api.client.xml.Xml;
import com.google.api.client.xml.XmlNamespaceDictionary;
import java.io.IOException;
import java.io.InputStream;
import org.xmlpull.v1.XmlPullParser;
import org.xmlpull.v1.XmlPullParserException;
/**
* {@link Beta}
* Abstract base class for an Atom feed parser when the feed type is known in advance.
*
* Implementation is not thread-safe.
*
* @param feed type
* @since 1.0
* @author Yaniv Inbar
*/
@Beta
public abstract class AbstractAtomFeedParser {
/** Whether the feed has been parsed. */
private boolean feedParsed;
/** XML pull parser to use. */
private final XmlPullParser parser;
/** Input stream to read. */
private final InputStream inputStream;
/** Feed class to parse. */
private final Class feedClass;
/** XML namespace dictionary. */
private final XmlNamespaceDictionary namespaceDictionary;
/**
* @param namespaceDictionary XML namespace dictionary
* @param parser XML pull parser to use
* @param inputStream input stream to read
* @param feedClass feed class to parse
* @since 1.5
*/
protected AbstractAtomFeedParser(
XmlNamespaceDictionary namespaceDictionary,
XmlPullParser parser,
InputStream inputStream,
Class feedClass) {
this.namespaceDictionary = Preconditions.checkNotNull(namespaceDictionary);
this.parser = Preconditions.checkNotNull(parser);
this.inputStream = Preconditions.checkNotNull(inputStream);
this.feedClass = Preconditions.checkNotNull(feedClass);
}
/**
* Returns the XML pull parser to use.
*
* @since 1.5
*/
public final XmlPullParser getParser() {
return parser;
}
/**
* Returns the input stream to read.
*
* @since 1.5
*/
public final InputStream getInputStream() {
return inputStream;
}
/**
* Returns the feed class to parse.
*
* @since 1.5
*/
public final Class getFeedClass() {
return feedClass;
}
/**
* Returns the XML namespace dictionary.
*
* @since 1.5
*/
public final XmlNamespaceDictionary getNamespaceDictionary() {
return namespaceDictionary;
}
/**
* Parse the feed and return a new parsed instance of the feed type. This method can be skipped if
* all you want are the items.
*
* @throws IOException I/O exception
* @throws XmlPullParserException XML pull parser exception
*/
public T parseFeed() throws IOException, XmlPullParserException {
boolean close = true;
try {
this.feedParsed = true;
T result = Types.newInstance(feedClass);
Xml.parseElement(parser, result, namespaceDictionary, Atom.StopAtAtomEntry.INSTANCE);
close = false;
return result;
} finally {
if (close) {
close();
}
}
}
/**
* Parse the next item in the feed and return a new parsed instance of the item type. If there is
* no item to parse, it will return {@code null} and automatically close the parser (in which case
* there is no need to call {@link #close()}.
*
* @throws IOException I/O exception
* @throws XmlPullParserException XML pull parser exception
*/
public Object parseNextEntry() throws IOException, XmlPullParserException {
if (!feedParsed) {
feedParsed = true;
Xml.parseElement(parser, null, namespaceDictionary, Atom.StopAtAtomEntry.INSTANCE);
}
boolean close = true;
try {
if (parser.getEventType() == XmlPullParser.START_TAG) {
Object result = parseEntryInternal();
parser.next();
close = false;
return result;
}
} finally {
if (close) {
close();
}
}
return null;
}
/** Closes the underlying parser. */
public void close() throws IOException {
inputStream.close();
}
/**
* Parses a single entry.
*
* @return object representing the entry
* @throws IOException I/O exception
* @throws XmlPullParserException XML pull parser exception
*/
protected abstract Object parseEntryInternal() throws IOException, XmlPullParserException;
}