javassist生成动态代理有两种方式：

• 方式一：代理工厂方式，与JDk动态代理和CGLIB类似

    // 代理工厂方式
    public static void testJavassistFactoryProxy() {
        // 创建代理工厂
        ProxyFactory proxyFactory = new ProxyFactory();
        // 设置被代理类型
        proxyFactory.setSuperclass(User.class);
        // 创建代理类的class
        Class<ProxyObject> proxyClass = proxyFactory.createClass();
        // 创建对象
        User userProxy = null;
        try {
             userProxy= (User)proxyClass.newInstance();
        } catch (InstantiationException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        }
        if(userProxy != null) {
            ((ProxyObject)userProxy).setHandler(new MethodHandler() {
                // 真实主题
                User user = new User();
                @Override
                public Object invoke(Object self, Method thisMethod, Method proceed, Object[] args) throws Throwable {
                    String beforeStr = "before";
                    Object str = thisMethod.invoke(user, args);
                    String afterStr = "after";
                    return beforeStr + str + afterStr;
                }
            });
            String exeStr = userProxy.exe();
            System.out.println(exeStr);
        }
    }

• 方式二：动态代码

    // 动态代码方式
    public static void testJavassistDefineClass() throws NotFoundException, CannotCompileException, IllegalAccessException, InstantiationException {
        // 创建类池, TRUE表示使用默认路径
        ClassPool classPool = new ClassPool();

        String className = User.class.getName();
        // 创建一个类 UserJavassistProxy
        CtClass ctClass = classPool.makeClass(className + "JavassistProxy");
        // 添加超类
        // 设置 UserJavassistProxy的父类是User
        ctClass.setSuperclass(classPool.get(User.class.getName()));
        // 添加默认的构造函数
        ctClass.addConstructor(CtNewConstructor.defaultConstructor(ctClass));
        // 添加属性
        ctClass.addField(CtField.make("public " + className
        + " real = new " + className + "()",ctClass));
        // 添加方法，里面进行动态代理逻辑
        ctClass.addMethod(CtMethod.make("public String exe() {return \"before \" + real.exe() + \" after\";}",ctClass));
        Class<User> userProxyClass = ctClass.toClass();
        User user = userProxyClass.newInstance();
        String exeStr = user.exe();
        System.out.println(exeStr);
    }

相关类：

package org.crown.lin;

import lombok.Data;

/**
 * @author ljq
 * @create 2019/10/18 0018
 */
@Data
public class User {

    private String name;
    private String sex;
    private String age;
    public String exe() {
        return "this is User.exe()";
    }

}