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javaFMI is a Java Library for the functional mock-up interface (or FMI). FMI defines a standardized interface to be used in computer simulations. The FMI Standard has beed developed by a large number of software companies and research centers that have worked in a cooperation project under the name of MODELISAR. This library addresses the connection of a java application with a FMU (functional mock-up unit).

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/*
 *  Copyright 2013-2016 SIANI - ULPGC
 *
 *  This File is part of JavaFMI Project
 *
 *  JavaFMI Project 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.
 *
 *  JavaFMI Project 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 JavaFMI. If not, see .
 */

package org.javafmi.kernel;

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.net.URLConnection;
import java.nio.file.Files;
import java.nio.file.Path;

import static org.javafmi.kernel.Files.close;
import static org.javafmi.kernel.Files.copyFromTo;

public class JarClassLoader extends ClassLoader {
    private File jarFile;
    private File outFolder;

    public JarClassLoader(File jarFile) {
        this.jarFile = jarFile;
        this.outFolder = getTempDirectory().toFile();
    }

    public Path getTempDirectory() {
        try {
            return Files.createTempDirectory(getClass().getName());
        } catch(IOException e) {
            throw new RuntimeException("Impossible to create temp directory to extract " + jarFile.getName());
        }
    }

    public Class loadClass(String className) {
        if(isAFrameworkClass(className) || isAJavaClass(className)) return loadCLassUsingSuperClassLoader(className);
        byte[] classData = getClassBytes(getClassUrl(replaceDotWithSlash(className)));
        return defineClass(className, classData, 0, classData.length);
    }

    public boolean isAFrameworkClass(String className) {
        return className.startsWith("org.javafmi.framework");
    }

    public boolean isAJavaClass(String className) {
        return className.startsWith("java");
    }

    private Class loadCLassUsingSuperClassLoader(String className) {
        try {
            return super.loadClass(className);
        } catch(ClassNotFoundException e) {
            try {
                return this.getClass().getClassLoader().loadClass(className);
            } catch (ClassNotFoundException e1) {
            }
            throw new RuntimeException(e);
        }
    }

    private String replaceDotWithSlash(String className) {
        while(className.indexOf('.') > 0)
            className = className.replace('.', '/');
        return className;
    }

    public URL getClassUrl(String className) {
        try {
            return new Unzipper(jarFile).unzip(className + ".class", outFolder).toURI().toURL();
        } catch(IOException e) {
            throw new RuntimeException("Problem getting the class URL " + className);
        }
    }

    private byte[] getClassBytes(URL classUrl) {
        InputStream input = getInputStreamFromConnection(classUrl);
        ByteArrayOutputStream buffer = new ByteArrayOutputStream();
        copyFromTo(input, buffer);
        close(input);
        close(buffer);
        return buffer.toByteArray();
    }

    private URLConnection openConnection(URL classUrl) {
        try {
            return classUrl.openConnection();
        } catch(IOException e) {
            throw new RuntimeException(e);
        }
    }

    private InputStream getInputStreamFromConnection(URL classUrl) {
        try {
            return openConnection(classUrl).getInputStream();
        } catch(IOException e) {
            throw new RuntimeException(e);
        }
    }
}