Java example source code file (JavaWrapper.java)

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class, classnotfoundexception, javawrapper, nosuchmethodexception, object, reflection, string

The JavaWrapper.java Java example source code

/*
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package com.sun.org.apache.bcel.internal.util;

/* ====================================================================
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2001 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
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 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
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 *    notice, this list of conditions and the following disclaimer in
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 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
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 * 4. The names "Apache" and "Apache Software Foundation" and
 *    "Apache BCEL" must not be used to endorse or promote products
 *    derived from this software without prior written permission. For
 *    written permission, please contact apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache",
 *    "Apache BCEL", nor may "Apache" appear in their name, without
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 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */

import java.lang.reflect.*;

/**
 * Java interpreter replacement, i.e., wrapper that uses its own ClassLoader
 * to modify/generate classes as they're requested. You can take this as a template
 * for your own applications.<br>
 * Call this wrapper with
 * <pre>java com.sun.org.apache.bcel.internal.util.JavaWrapper <real.class.name> [arguments]

* <p> * To use your own class loader you can set the "bcel.classloader" system property * which defaults to "com.sun.org.apache.bcel.internal.util.ClassLoader", e.g., with * <pre>java com.sun.org.apache.bcel.internal.util.JavaWrapper -Dbcel.classloader=foo.MyLoader <real.class.name> [arguments] * </p> * * @version $Id: JavaWrapper.java,v 1.3 2007-07-19 04:34:52 ofung Exp $ * @author <A HREF="mailto:markus.dahm@berlin.de">M. Dahm * @see ClassLoader */ public class JavaWrapper { private java.lang.ClassLoader loader; private static java.lang.ClassLoader getClassLoader() { String s = SecuritySupport.getSystemProperty("bcel.classloader"); if((s == null) || "".equals(s)) s = "com.sun.org.apache.bcel.internal.util.ClassLoader"; try { return (java.lang.ClassLoader)Class.forName(s).newInstance(); } catch(Exception e) { throw new RuntimeException(e.toString()); } } public JavaWrapper(java.lang.ClassLoader loader) { this.loader = loader; } public JavaWrapper() { this(getClassLoader()); } /** Runs the _main method of the given class with the arguments passed in argv * * @param class_name the fully qualified class name * @param argv the arguments just as you would pass them directly */ public void runMain(String class_name, String[] argv) throws ClassNotFoundException { Class cl = loader.loadClass(class_name); Method method = null; try { method = cl.getMethod("_main", new Class[] { argv.getClass() }); /* Method _main is sane ? */ int m = method.getModifiers(); Class r = method.getReturnType(); if(!(Modifier.isPublic(m) && Modifier.isStatic(m)) || Modifier.isAbstract(m) || (r != Void.TYPE)) throw new NoSuchMethodException(); } catch(NoSuchMethodException no) { System.out.println("In class " + class_name + ": public static void _main(String[] argv) is not defined"); return; } try { method.invoke(null, new Object[] { argv }); } catch(Exception ex) { ex.printStackTrace(); } } /** Default _main method used as wrapper, expects the fully qualified class name * of the real class as the first argument. */ public static void _main(String[] argv) throws Exception { /* Expects class name as first argument, other arguments are by-passed. */ if(argv.length == 0) { System.out.println("Missing class name."); return; } String class_name = argv[0]; String[] new_argv = new String[argv.length - 1]; System.arraycopy(argv, 1, new_argv, 0, new_argv.length); JavaWrapper wrapper = new JavaWrapper(); wrapper.runMain(class_name, new_argv); } }