https://github.com/cglib/cglib/cglib: cglib is a powerful, high performance and quality Code Generation Library, It is used to extend JAVA classes and implements interfaces at runtime. 
/*
 * Copyright 2003 The Apache Software Foundation
 *
 *  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 net.sf.cglib.transform;

import net.sf.cglib.core.ClassGenerator;
import net.sf.cglib.core.Transformer;
import org.objectweb.asm.ClassVisitor;

public class TransformingClassGenerator implements ClassGenerator {
    private ClassGenerator gen;
    private ClassTransformer t;
    
    public TransformingClassGenerator(ClassGenerator gen, ClassTransformer t) {
        this.gen = gen;
        this.t = t;
    }
    
    public void generateClass(ClassVisitor v) throws Exception {
        t.setTarget(v);
        gen.generateClass(t);
    }
}