cc.vidr.datum.util.FreebaseUtils.java Source code

Introduction

Here is the source code for cc.vidr.datum.util.FreebaseUtils.java

Source

/*
 * Copyright (C) 2010  David Roberts <d@vidr.cc>
 * 
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 * 
 * This program 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 Affero General Public License for more details.
 * 
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

package cc.vidr.datum.util;

import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.net.URL;
import java.net.URLConnection;
import java.util.List;

import org.json.simple.JSONObject;
import org.json.simple.JSONValue;
import org.json.simple.parser.ParseException;

import cc.vidr.datum.term.Atom;
import cc.vidr.datum.term.DateTimeTerm;
import cc.vidr.datum.term.FloatTerm;
import cc.vidr.datum.term.IntegerTerm;
import cc.vidr.datum.term.StringTerm;
import cc.vidr.datum.term.Term;

/**
 * Methods for interacting with Freebase.com
 * 
 * @author  David Roberts
 */
public final class FreebaseUtils {
    private static final String endpoint = "http://api.freebase.com/api/";

    /**
     * Prevent instantiation.
     */
    private FreebaseUtils() {
    }

    /**
     * Return the list of JSON objects returned by the API for the given query.
     * 
     * @param path  the API service path
     * @return      the list of JSON objects
     * @throws      IOException if there was an error communicating with the
     *              server
     * @throws      ParseException if the server returns malformed JSON
     */
    @SuppressWarnings("unchecked")
    public static List<JSONObject> getResultList(String path) throws IOException, ParseException {
        URLConnection connection = new URL(endpoint + path).openConnection();
        connection.connect();
        InputStream stream = connection.getInputStream();
        Reader reader = new InputStreamReader(stream);
        JSONObject o = (JSONObject) JSONValue.parse(reader);
        return (List<JSONObject>) o.get("result");
    }

    /**
     * Return the MQL/JSON string representation of the given term.
     * 
     * @param term  the term
     * @return      the string representation
     */
    public static String termToString(Term term) {
        if (term.isVariable())
            return "null";
        if (term instanceof Atom) {
            String s = term.toString();
            if (s.startsWith("freebase:guid:"))
                return "\"/guid/" + s.substring("freebase:guid:".length()) + "\"";
            return "\"/en/" + s + "\"";
        }
        if (term instanceof DateTimeTerm)
            return '"' + term.toString() + '"';
        if (term instanceof StringTerm || term instanceof FloatTerm || term instanceof IntegerTerm)
            return term.toString();
        throw new IllegalArgumentException("Unsupported type: " + term);
    }

    /**
     * Return the MQL/JSON object representation for the given term.
     * 
     * @param term  the term
     * @param type  the type of the MQL object
     * @return      the JSON representation
     */
    public static String termToJSON(Term term, String type) {
        if (type.equals("object"))
            return "{\"id\":" + termToString(term) + "}";
        if (type.equals("text"))
            return "{\"lang\":\"/lang/en\"," + "\"value\":" + termToString(term) + "}";
        if (type.equals("datetime") || type.equals("float") || type.equals("int"))
            return "{\"value\":" + termToString(term) + "}";
        throw new IllegalArgumentException("Invalid type: " + type);
    }

    /**
     * Return the term represented by the given MQL/JSON object.
     * 
     * @param o     the JSON object
     * @param type  the type of the MQL object
     * @return      the term
     */
    public static Term termFromJSON(JSONObject o, String type) {
        if (type.equals("object"))
            return FreebaseUtils.atomFromID((String) o.get("id"));
        if (type.equals("text"))
            return new StringTerm((String) o.get("value"));
        if (type.equals("datetime"))
            return new DateTimeTerm((String) o.get("value"));
        if (type.equals("float"))
            return new FloatTerm((Number) o.get("value"));
        if (type.equals("int"))
            return new IntegerTerm((Number) o.get("value"));
        throw new IllegalArgumentException("Invalid type: " + type);
    }

    /**
     * Return the atom corresponding to the given Freebase ID.
     * 
     * @param id  the Freebase ID
     * @return    the atom
     */
    public static Atom atomFromID(String id) {
        if (id.startsWith("/en/"))
            return new Atom(id.substring("/en/".length()));
        if (id.startsWith("/guid/"))
            return new Atom("freebase:guid:" + id.substring("/guid/".length()));
        throw new IllegalArgumentException("Unsupported domain: " + id);
    }
}