1   package org.apache.bcel.util;
2   
3   /* ====================================================================
4    * The Apache Software License, Version 1.1
5    *
6    * Copyright (c) 2001 The Apache Software Foundation.  All rights
7    * reserved.
8    *
9    * Redistribution and use in source and binary forms, with or without
10   * modification, are permitted provided that the following conditions
11   * are met:
12   *
13   * 1. Redistributions of source code must retain the above copyright
14   *    notice, this list of conditions and the following disclaimer.
15   *
16   * 2. Redistributions in binary form must reproduce the above copyright
17   *    notice, this list of conditions and the following disclaimer in
18   *    the documentation and/or other materials provided with the
19   *    distribution.
20   *
21   * 3. The end-user documentation included with the redistribution,
22   *    if any, must include the following acknowledgment:
23   *       "This product includes software developed by the
24   *        Apache Software Foundation (http://www.apache.org/)."
25   *    Alternately, this acknowledgment may appear in the software itself,
26   *    if and wherever such third-party acknowledgments normally appear.
27   *
28   * 4. The names "Apache" and "Apache Software Foundation" and
29   *    "Apache BCEL" must not be used to endorse or promote products
30   *    derived from this software without prior written permission. For
31   *    written permission, please contact apache@apache.org.
32   *
33   * 5. Products derived from this software may not be called "Apache",
34   *    "Apache BCEL", nor may "Apache" appear in their name, without
35   *    prior written permission of the Apache Software Foundation.
36   *
37   * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
38   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
39   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
40   * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
41   * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
42   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
43   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
44   * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
45   * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
46   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
47   * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
48   * SUCH DAMAGE.
49   * ====================================================================
50   *
51   * This software consists of voluntary contributions made by many
52   * individuals on behalf of the Apache Software Foundation.  For more
53   * information on the Apache Software Foundation, please see
54   * <http://www.apache.org/>.
55   */
56  
57  import java.lang.reflect.*;
58  
59  /***
60   * Java interpreter replacement, i.e., wrapper that uses its own ClassLoader
61   * to modify/generate classes as they're requested. You can take this as a template
62   * for your own applications.<br>
63   * Call this wrapper with
64   * <pre>java org.apache.bcel.util.JavaWrapper <real.class.name> [arguments]</pre>
65   * <p>
66   * To use your own class loader you can set the "bcel.classloader" system property
67   * which defaults to "org.apache.bcel.util.ClassLoader", e.g., with
68   * <pre>java org.apache.bcel.util.JavaWrapper -Dbcel.classloader=foo.MyLoader <real.class.name> [arguments]</pre>
69   * </p>
70   *
71   * @version $Id: JavaWrapper.java,v 1.1.1.1 2001/10/29 20:00:30 jvanzyl Exp $
72   * @author  <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A>
73   * @see ClassLoader
74   */
75  public class JavaWrapper {
76    private java.lang.ClassLoader loader;
77  
78    private static java.lang.ClassLoader getClassLoader() {
79      String s = System.getProperty("bcel.classloader");
80  
81      if((s == null) || "".equals(s))
82        s = "org.apache.bcel.util.ClassLoader";
83  
84      try {
85        return (java.lang.ClassLoader)Class.forName(s).newInstance();
86      } catch(Exception e) {
87        throw new RuntimeException(e.toString());
88      }
89    }
90        
91    public JavaWrapper(java.lang.ClassLoader loader) {
92      this.loader = loader;
93    }
94  
95    public JavaWrapper() {
96      this(getClassLoader());
97    }
98  
99    /*** Runs the main method of the given class with the arguments passed in argv
100    *
101    * @param class_name the fully qualified class name
102    * @param argv the arguments just as you would pass them directly
103    */
104   public void runMain(String class_name, String[] argv) throws ClassNotFoundException
105   {
106     Class   cl    = loader.loadClass(class_name);
107     Method method = null;
108 
109     try {
110       method = cl.getMethod("main",  new Class[] { argv.getClass() });
111       
112       /* Method main is sane ?
113        */
114       int   m = method.getModifiers();
115       Class r = method.getReturnType();
116       
117       if(!(Modifier.isPublic(m) && Modifier.isStatic(m)) ||
118 	 Modifier.isAbstract(m) || (r != Void.TYPE))
119 	throw new NoSuchMethodException();
120     } catch(NoSuchMethodException no) {
121       System.out.println("In class " + class_name +
122 			 ": public static void main(String[] argv) is not defined");
123       return;
124     }
125     
126     try {
127       method.invoke(null, new Object[] { argv });
128     } catch(Exception ex) {
129       ex.printStackTrace();
130     }
131   }
132 
133   /*** Default main method used as wrapper, expects the fully qualified class name
134    * of the real class as the first argument.
135    */
136   public static void main(String[] argv) throws Exception {
137     /* Expects class name as first argument, other arguments are by-passed.
138      */
139     if(argv.length == 0) {
140       System.out.println("Missing class name.");
141       return;
142     }
143 
144     String class_name = argv[0];
145     String[] new_argv = new String[argv.length - 1];
146     System.arraycopy(argv, 1, new_argv, 0, new_argv.length);
147 
148     JavaWrapper wrapper = new JavaWrapper();
149     wrapper.runMain(class_name, new_argv);
150   }
151 }
152 
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