trunk/tika-parsers/src/main/java/org/apache/tika/parser/pdf/PDF2XHTML.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.tika.parser.pdf;

import java.io.IOException;
import java.io.Writer;

import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.pdmodel.PDPage;
import org.apache.pdfbox.util.PDFTextStripper;
import org.apache.pdfbox.util.TextPosition;
import org.apache.tika.exception.TikaException;
import org.apache.tika.io.IOExceptionWithCause;
import org.apache.tika.metadata.Metadata;
import org.apache.tika.sax.XHTMLContentHandler;
import org.xml.sax.ContentHandler;
import org.xml.sax.SAXException;

/**
 * Utility class that overrides the {@link PDFTextStripper} functionality
 * to produce a semi-structured XHTML SAX events instead of a plain text
 * stream.
 */
class PDF2XHTML extends PDFTextStripper {

    /**
     * Converts the given PDF document (and related metadata) to a stream
     * of XHTML SAX events sent to the given content handler.
     *
     * @param document PDF document
     * @param handler SAX content handler
     * @param metadata PDF metadata
     * @throws SAXException if the content handler fails to process SAX events
     * @throws TikaException if the PDF document can not be processed
     */
    public static void process(
            PDDocument document, ContentHandler handler, Metadata metadata)
            throws SAXException, TikaException {
        try {
            // Extract text using a dummy Writer as we override the
            // key methods to output to the given content handler.
            new PDF2XHTML(handler, metadata).writeText(document, new Writer() {
                @Override
                public void write(char[] cbuf, int off, int len) {
                }
                @Override
                public void flush() {
                }
                @Override
                public void close() {
                }
            });
        } catch (IOException e) {
            if (e.getCause() instanceof SAXException) {
                throw (SAXException) e.getCause();
            } else {
                throw new TikaException("Unable to extract PDF content", e);
            }
        }
    }

    private final XHTMLContentHandler handler;

    private PDF2XHTML(ContentHandler handler, Metadata metadata)
            throws IOException {
        this.handler = new XHTMLContentHandler(handler, metadata);
        setForceParsing(true);
        setSortByPosition(true);
    }

    @Override
    protected void startDocument(PDDocument pdf) throws IOException {
        try {
            handler.startDocument();
        } catch (SAXException e) {
            throw new IOExceptionWithCause("Unable to start a document", e);
        }
    }

    @Override
    protected void endDocument(PDDocument pdf) throws IOException {
        try {
            handler.endDocument();
        } catch (SAXException e) {
            throw new IOExceptionWithCause("Unable to end a document", e);
        }
    }

    @Override
    protected void startPage(PDPage page) throws IOException {
        try {
            handler.startElement("div", "class", "page");
            handler.startElement("p");
        } catch (SAXException e) {
            throw new IOExceptionWithCause("Unable to start a page", e);
        }
    }

    @Override
    protected void endPage(PDPage page) throws IOException {
        try {
            handler.endElement("p");
            handler.endElement("div");
        } catch (SAXException e) {
            throw new IOExceptionWithCause("Unable to end a page", e);
        }
    }

    @Override
    protected void writeString(String text) throws IOException {
        try {
            handler.characters(text);
        } catch (SAXException e) {
            throw new IOExceptionWithCause(
                    "Unable to write a string: " + text, e);
        }
    }

    @Override
    protected void writeCharacters(TextPosition text) throws IOException {
        try {
            handler.characters(text.getCharacter());
        } catch (SAXException e) {
            throw new IOExceptionWithCause(
                    "Unable to write a character: " + text.getCharacter(), e);
        }
    }

    @Override
    protected void writeWordSeparator() throws IOException {
        try {
            handler.characters(" ");
        } catch (SAXException e) {
            throw new IOExceptionWithCause(
                    "Unable to write a space character", e);
        }
    }

    @Override
    protected void writeLineSeparator() throws IOException {
        try {
            handler.characters("\n");
        } catch (SAXException e) {
            throw new IOExceptionWithCause(
                    "Unable to write a newline character", e);
        }
    }

}