HttpOpener.java

/*
 * 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.io;

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

import org.culturegraph.mf.framework.FluxCommand;
import org.culturegraph.mf.framework.MetafactureException;
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.framework.helpers.DefaultObjectPipe;


/**
 * Opens a {@link URLConnection} and passes a reader to the receiver.
 *
 * @author Christoph Böhme
 * @author Jan Schnasse
 *
 */
@Description("Opens a http resource. Supports the setting of Accept and Accept-Charset as http header fields.")
@In(String.class)
@Out(java.io.Reader.class)
@FluxCommand("open-http")
public final class HttpOpener
		extends DefaultObjectPipe<String, ObjectReceiver<Reader>> {

	private String encoding = "UTF-8";
	private String accept = "*/*";

	/**
	 * Sets the HTTP accept header value. This is a mime-type such as text/plain
	 * or text/html. The default value of the accept is */* which means
	 * any mime-type.
	 */
	public void setAccept(final String accept) {
		this.accept = accept;
	}

	/**
	 * Sets the preferred encoding of the HTTP response. This value is in the
	 * accept-charset header. Additonally, the encoding is used for reading the
	 * HTTP resonse if it does not  specify an encoding. The default value for
	 * the encoding is UTF-8.
	 */
	public void setEncoding(final String encoding) {
		this.encoding = encoding;
	}

	@Override
	public void process(final String urlStr) {
		try {
			final URL url = new URL(urlStr);
			final URLConnection con = url.openConnection();
			con.addRequestProperty("Accept", accept);
			con.addRequestProperty("Accept-Charset", encoding);
			String enc = con.getContentEncoding();
			if (enc == null) {
				enc = encoding;
			}
			getReceiver().process(new InputStreamReader(con.getInputStream(), enc));
		} catch (IOException e) {
			throw new MetafactureException(e);
		}
	}
}