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Groovy: A powerful, dynamic language for the JVM

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/*
 * Copyright 2003-2012 the original author or authors.
 *
 * 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.codehaus.groovy.control;

import groovy.lang.GroovyRuntimeException;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.URL;
import java.util.Enumeration;
import java.util.LinkedHashSet;
import java.util.Set;

/**
 * Looks for source file extensions in META-INF/services/org.codehaus.groovy.source.Extensions
 */
public class SourceExtensionHandler {

    public static Set getRegisteredExtensions(ClassLoader loader) {
        Set extensions = new LinkedHashSet();
        extensions.add("groovy");
        try {
            Enumeration globalServices = loader.getResources("META-INF/services/org.codehaus.groovy.source.Extensions");
            while (globalServices.hasMoreElements()) {
                BufferedReader svcIn = null;
                URL service = globalServices.nextElement();
                try {
                    svcIn = new BufferedReader(new InputStreamReader(service.openStream()));
                    String extension = svcIn.readLine();
                    while (extension != null) {
                        extension = extension.trim();
                        if (!extension.startsWith("#") && extension.length() > 0) {
                            extensions.add(extension);
                        }
                        extension = svcIn.readLine();
                    }
                } catch (IOException ex) {
                    throw new GroovyRuntimeException("IO Exception attempting to load registered source extension " +
                            service.toExternalForm() + ". Exception: " + ex.toString());
                } finally {
                    if (svcIn != null) svcIn.close();
                }
            }
        } catch (IOException ex) {
            throw new GroovyRuntimeException("IO Exception getting registered source extensions. Exception: " + ex.toString());
        }
        return extensions;
    }
}