org.culturegraph.mf.stream.pipe.TripleObjectRetriever.java Source code

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Here is the source code for org.culturegraph.mf.stream.pipe.TripleObjectRetriever.java

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/*
 *  Copyright 2013, 2014 Deutsche Nationalbibliothek
 *
 *  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 org.culturegraph.mf.stream.pipe;

import java.io.IOException;
import java.net.URL;
import java.net.URLConnection;

import org.apache.commons.io.IOUtils;
import org.culturegraph.mf.exceptions.MetafactureException;
import org.culturegraph.mf.framework.DefaultObjectPipe;
import org.culturegraph.mf.framework.ObjectReceiver;
import org.culturegraph.mf.framework.annotations.Description;
import org.culturegraph.mf.framework.annotations.In;
import org.culturegraph.mf.framework.annotations.Out;
import org.culturegraph.mf.types.Triple;
import org.culturegraph.mf.types.Triple.ObjectType;

/**
 * Uses the object value of the triple as a URL and emits a new triple
 * in which the object value is replaced with the contents of the resource
 * identified by the URL.
 * 
 * @author Christoph Bhme
 */
@Description("Uses the object value of the triple as a URL and emits a new triple "
        + "in which the object value is replaced with the contents of the resource " + "identified by the URL.")
@In(Triple.class)
@Out(Triple.class)
public final class TripleObjectRetriever extends DefaultObjectPipe<Triple, ObjectReceiver<Triple>> {

    private String defaultEncoding = "UTF-8";

    /**
     * Returns the default encoding used when no encoding is
     * provided by the server. The default setting is UTF-8.
     * 
     * @return current default setting
     */
    public String getDefaultEncoding() {
        return defaultEncoding;
    }

    /**
     * Sets the default encoding to use when no encoding is 
     * provided by the server. The default setting is UTF-8.
     * 
     * @param defaultEncoding new default encoding
     */
    public void setDefaultEncoding(final String defaultEncoding) {
        this.defaultEncoding = defaultEncoding;
    }

    @Override
    public void process(final Triple triple) {
        assert !isClosed();

        if (triple.getObjectType() != ObjectType.STRING) {
            return;
        }

        final String objectValue;
        try {
            final URL url = new URL(triple.getObject());
            final URLConnection con = url.openConnection();
            String enc = con.getContentEncoding();
            if (enc == null) {
                enc = defaultEncoding;
            }
            objectValue = IOUtils.toString(con.getInputStream(), enc);
        } catch (IOException e) {
            throw new MetafactureException(e);
        }

        getReceiver().process(new Triple(triple.getSubject(), triple.getPredicate(), objectValue));
    }

}