muscle.core.conduit.terminal.JSONSource.java Source code

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Here is the source code for muscle.core.conduit.terminal.JSONSource.java

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/*
* Copyright 2008, 2009 Complex Automata Simulation Technique (COAST) consortium
* Copyright 2010-2013 Multiscale Applications on European e-Infrastructures (MAPPER) project
*
* GNU Lesser General Public License
* 
* This file is part of MUSCLE (Multiscale Coupling Library and Environment).
* 
* MUSCLE is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
* 
* MUSCLE is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
* GNU Lesser General Public License for more details.
* 
* You should have received a copy of the GNU Lesser General Public License
* along with MUSCLE.  If not, see <http://www.gnu.org/licenses/>.
*/
package muscle.core.conduit.terminal;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.HashMap;
import java.util.logging.Level;
import java.util.logging.Logger;
import muscle.core.model.Observation;
import muscle.core.model.Timestamp;
import org.json.simple.JSONObject;
import org.json.simple.JSONValue;

/**
 * Reads JSON data from a URL
 * @author Joris Borgdorff
 */
public class JSONSource extends Source<HashMap<String, Object>> {
    int iteration = 0;
    URL url;

    @Override
    public void beforeExecute() {
        try {
            // Get data from web
            url = new URL(getProperty("url"));
        } catch (MalformedURLException ex) {
            Logger.getLogger(JSONSource.class.getName()).log(Level.SEVERE,
                    "Could not parse url parameter to use with JSON source", ex);
            throw new RuntimeException(ex);
        }
    }

    @Override
    /**
     * Get the JSON HashMap from the given URL.
     * The keys of the hashmap are keys, the objects should be tested for their
     * datatype, which can be Boolean, Long, String, HashMap or Double, ArrayList or null.
     */
    protected Observation<HashMap<String, Object>> generate() throws InterruptedException {
        BufferedReader in = null;
        Observation<HashMap<String, Object>> obs = null;

        try {
            in = new BufferedReader(new InputStreamReader(url.openStream()));
            JSONObject jsonHash = (JSONObject) JSONValue.parse(in);

            // Will only work if the keys of the JSON object are strings, which
            // they always are.
            @SuppressWarnings("unchecked")
            HashMap<String, Object> map = new HashMap<String, Object>(jsonHash);

            // Each iteration simply takes the old timestamp and a new timestamp
            obs = new Observation<HashMap<String, Object>>(map, new Timestamp(iteration),
                    new Timestamp(++iteration));
        } catch (IOException ex) {
            Logger.getLogger(JSONSource.class.getName()).log(Level.SEVERE,
                    "Can not connect to URL <" + url + "> with JSON source.", ex);
        } finally {
            try {
                if (in != null)
                    in.close();
            } catch (IOException ex) {
            }
        }

        return obs;
    }

    @Override
    /** Will always be able to get a new data point by polling the URL again, so never empty */
    public boolean isEmpty() {
        return false;
    }
}