Creating your own Text extractor

You can create your own Text Extractor.

Conditions:

• The new Text Extractor class must implement the “TextExtractor” interface.
• The new Text Extractor class must be declared in the package “com.openkm.plugin.extractor”.
• The new Text Extractor class must be annotated with “@PluginImplementation”.
• The new Text Extractor class must extend “AbstractTextExtractor”.

Text Extractor interface:

package com.openkm.plugin.extractor;

import net.xeoh.plugins.base.Plugin;

import java.io.IOException;
import java.io.InputStream;

public interface TextExtractor extends Plugin {

    String[] getContentTypes();

    String extractText(InputStream stream, String mimeType, String encoding) throws IOException;
}

The new class must be loaded into the package com.openkm.plugin.extractor because the application plugin system will try to load it from there.

Caution

Do not omit the tag @PluginImplementation; otherwise, the application plugin system will not be able to retrieve the new class.

Note

More information is available at Register a new plugin.

Method descriptions

Method	Type	Description
getContentTypes()	String[]	Returns the MIME types supported by this extractor. The returned strings must be in lower case, and the returned array must not be empty.
extractText(InputStream stream, String mimeType, String encoding)	String	Returns a reader for the text content of the given binary document. The content type and character encoding (if available and applicable) are given as arguments.

Example of the Text Extractor implementation

package com.openkm.plugin.extractor;

import net.xeoh.plugins.base.annotations.PluginImplementation;
import org.apache.commons.io.IOUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;
import java.nio.charset.StandardCharsets;

/**
 * Text extractor for plain text.
 */
@PluginImplementation
public class PlainTextExtractor extends AbstractTextExtractor {

    private static final Logger log = LoggerFactory.getLogger(PlainTextExtractor.class);

    /**
     * Creates a new <code>PlainTextExtractor</code> instance.
     */
    public PlainTextExtractor() {
        super(new String[]{"text/plain"});
    }

    // -------------------------------------------------------< TextExtractor >
    /**
     * Wraps the given input stream to an {@link InputStreamReader} using the
     * given encoding, or the platform default encoding if the encoding is not
     * given or is unsupported. Closes the stream and returns an empty reader if
     * the given encoding is not supported.
     *
     * @param stream binary stream
     * @param type ignored
     * @param encoding character encoding, optional
     * @return reader for the plain text content
     * @throws IOException if the binary stream can not be closed in case of an
     * encoding issue
     */
    @Override
    public String extractText(InputStream stream, String type, String encoding) throws IOException {
        log.debug("extractText({}, {}, {})", stream, type, encoding);

        try {
            if (encoding != null) {
                return IOUtils.toString(stream, encoding);
            }
        } catch (UnsupportedEncodingException e) {
            log.warn("Unsupported encoding '{}', using default ({}) instead.", encoding, System.getProperty("file.encoding"));
        }

        return IOUtils.toString(stream, StandardCharsets.UTF_8);
    }
}