org.apache.tika.sax.StandardsExtractingContentHandler Maven / Gradle / Ivy
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/*
* 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.tika.sax;
import java.util.Arrays;
import java.util.List;
import org.xml.sax.ContentHandler;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;
import org.apache.tika.metadata.Metadata;
/**
* StandardsExtractingContentHandler is a Content Handler used to extract
* standard references while parsing.
*
* This handler relies on complex regular expressions which can be slow on some types of
* input data.
*/
public class StandardsExtractingContentHandler extends ContentHandlerDecorator {
public static final String STANDARD_REFERENCES = "standard_references";
private final Metadata metadata;
private final StringBuilder stringBuilder;
private int maxBufferLength = 100000;
private double threshold = 0;
/**
* Creates a decorator for the given SAX event handler and Metadata object.
*
* @param handler SAX event handler to be decorated.
* @param metadata {@link Metadata} object.
*/
public StandardsExtractingContentHandler(ContentHandler handler, Metadata metadata) {
super(handler);
this.metadata = metadata;
this.stringBuilder = new StringBuilder();
}
/**
* Creates a decorator that by default forwards incoming SAX events to a
* dummy content handler that simply ignores all the events. Subclasses
* should use the {@link #setContentHandler(ContentHandler)} method to
* switch to a more usable underlying content handler. Also creates a dummy
* Metadata object to store phone numbers in.
*/
protected StandardsExtractingContentHandler() {
this(new DefaultHandler(), new Metadata());
}
/**
* Gets the threshold to be used for selecting the standard references found
* within the text based on their score.
*
* @return the threshold to be used for selecting the standard references
* found within the text based on their score.
*/
public double getThreshold() {
return threshold;
}
/**
* Sets the score to be used as threshold.
*
* @param score the score to be used as threshold.
*/
public void setThreshold(double score) {
this.threshold = score;
}
/**
* The characters method is called whenever a Parser wants to pass raw
* characters to the ContentHandler. However, standard references are often
* split across different calls to characters, depending on the specific
* Parser used. Therefore, we simply add all characters to a StringBuilder
* and analyze it once the document is finished.
*/
@Override
public void characters(char[] ch, int start, int length) throws SAXException {
try {
if (maxBufferLength > -1) {
int remaining = maxBufferLength - stringBuilder.length();
length = remaining > length ? length : remaining;
}
String text = new String(Arrays.copyOfRange(ch, start, start + length));
stringBuilder.append(text);
super.characters(ch, start, length);
} catch (SAXException e) {
handleException(e);
}
}
/**
* This method is called whenever the Parser is done parsing the file. So,
* we check the output for any standard references.
*/
@Override
public void endDocument() throws SAXException {
super.endDocument();
List standards =
StandardsText.extractStandardReferences(stringBuilder.toString(), threshold);
for (StandardReference standardReference : standards) {
metadata.add(STANDARD_REFERENCES, standardReference.toString());
}
}
/**
* The number of characters to store in memory for checking for standards.
*
* If this is unbounded, the complex regular expressions can take a long time
* to process some types of data. Only increase this limit with great caution.
*/
public void setMaxBufferLength(int maxBufferLength) {
this.maxBufferLength = maxBufferLength;
}
}