net.ontopia.topicmaps.query.impl.basic.JavaModule.java Source code

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Here is the source code for net.ontopia.topicmaps.query.impl.basic.JavaModule.java

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/*
 * #!
 * Ontopia Engine
 * #-
 * Copyright (C) 2001 - 2013 The Ontopia Project
 * #-
 * 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 net.ontopia.topicmaps.query.impl.basic;

import java.util.HashMap;
import java.util.Map;
import net.ontopia.topicmaps.core.TopicMapIF;
import net.ontopia.topicmaps.query.parser.ModuleIF;
import net.ontopia.topicmaps.query.parser.PredicateIF;
import net.ontopia.topicmaps.query.spi.JavaPredicate;
import net.ontopia.topicmaps.query.spi.SearcherIF;
import net.ontopia.utils.OntopiaRuntimeException;
import org.apache.commons.lang3.StringUtils;

/**
 * EXPERIMENTAL: A query module that is able to instantiate predicates
 * when given a java class name.<p>
 */
public class JavaModule implements ModuleIF {

    public static final String MODULE_PREFIX = "urn:x-java:";

    protected TopicMapIF topicmap;
    protected String moduleURI;

    public JavaModule(TopicMapIF topicmap, String moduleURI) {
        this.topicmap = topicmap;
        this.moduleURI = moduleURI;
    }

    @Override
    public PredicateIF getPredicate(String name) {
        // figure out which class to use
        String className = moduleURI.substring(MODULE_PREFIX.length());
        int qmix = className.indexOf('?');
        String parameters = null;
        if (qmix >= 0) {
            parameters = className.substring(qmix + 1);
            className = className.substring(0, qmix);
        }
        Class klass = null;
        try {
            ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
            klass = Class.forName(className, true, classLoader);
        } catch (Exception e) {
            throw new OntopiaRuntimeException("Java module class '" + className + "' cannot be found.", e);
        }

        try {
            Object o = klass.newInstance();
            if (o instanceof SearcherIF) {
                SearcherIF searcher = (SearcherIF) o;
                searcher.setModuleURI(moduleURI);
                searcher.setPredicateName(name);
                searcher.setTopicMap(topicmap);
                searcher.setParameters(parseParameters(parameters));
                return new JavaSearcherPredicate(name, topicmap, searcher);
            } else if (o instanceof JavaPredicate) {
                JavaPredicate pred = (JavaPredicate) o;
                pred.setModuleURI(moduleURI);
                pred.setPredicateName(name);
                pred.setTopicMap(topicmap);
                pred.setParameters(parseParameters(parameters));
                return pred;
            }

        } catch (Exception e) {
            throw new OntopiaRuntimeException("Java module class '" + className + "' cannot be instantiated.", e);
        }
        throw new OntopiaRuntimeException("Java module class '" + className + "' of unknown type.");
    }

    protected Map parseParameters(String parameters) {
        Map result = new HashMap();
        if (parameters != null) {
            String[] tokens = StringUtils.split(parameters, "&");
            for (int i = 0; i < tokens.length; i++) {
                String[] vals = StringUtils.split(tokens[i], "=");
                result.put(vals[0], vals[1]);
            }
        }
        return result;
    }

}