src/examples/Id.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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
 *
 *   https://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.
 */

import org.apache.bcel.Repository;
import org.apache.bcel.classfile.ClassParser;
import org.apache.bcel.classfile.Field;
import org.apache.bcel.classfile.JavaClass;
import org.apache.bcel.classfile.Method;
import org.apache.bcel.generic.ClassGen;
import org.apache.bcel.generic.FieldGen;
import org.apache.bcel.generic.MethodGen;

/**
 * Test BCEL if an input file is identical to the outfile generated with BCEL. Of course there may some small
 * differences, for example, because BCEL generates local variable tables by default.
 *
 * Try to:
 *
 * <pre>
 * % java Id <someclass> % java listclass -code <someclass> &gt; foo % java listclass -code <someclass>.clazz &gt; bar %
 * diff foo bar | more
 *
 * <pre>
 */
public class Id {

    public static void main(final String[] argv) throws Exception {
        JavaClass clazz;

        if ((clazz = Repository.lookupClass(argv[0])) == null) {
            clazz = new ClassParser(argv[0]).parse(); // May throw IOException
        }

        final ClassGen cg = new ClassGen(clazz);

        for (final Method method : clazz.getMethods()) {
            final MethodGen mg = new MethodGen(method, cg.getClassName(), cg.getConstantPool());
            cg.replaceMethod(method, mg.getMethod());
        }

        for (final Field field : clazz.getFields()) {
            final FieldGen fg = new FieldGen(field, cg.getConstantPool());
            cg.replaceField(field, fg.getField());
        }

        cg.getJavaClass().dump(clazz.getClassName() + ".clazz");
    }
}