动态代理中的调用处理器接口（InvocationHandler）invoke方法的参数args为啥不能传递自定义类对象

Question

正在学习core java的第六章中的proxy这一小节，感觉非常有意思，下面是书中举例的代码

package proxy;

import java.lang.reflect.*;
import java.util.*;

public class ProxyTest
{
   public static void main(String[] args)
   {
      Object[] elements = new Object[1000];

      // fill elements with proxies for the integers 1 ... 1000
      for (int i = 0; i < elements.length; i++)
      {
         Integer value = i + 1;
         InvocationHandler handler = new TraceHandler(value);
         Object proxy = Proxy.newProxyInstance(null, new Class[] { Comparable.class } , handler);
         elements[i] = proxy;
      }

      // construct a random integer
      Integer key = new Random().nextInt(elements.length) + 1;

      // search for the key
      int result = Arrays.binarySearch(elements, key);

      // print match if found
      if (result >= 0) System.out.println(elements[result]);
   }
}

/**
 * An invocation handler that prints out the method name and parameters, then
 * invokes the original method
 */
class TraceHandler implements InvocationHandler
{
   private Object target;

   /**
    * Constructs a TraceHandler
    * @param t the implicit parameter of the method call
    */
   public TraceHandler(Object t)
   {
      target = t;
   }

   public Object invoke(Object proxy, Method m, Object[] args) throws Throwable
   {
      // print implicit argument
      System.out.print(target);
      // print method name
      System.out.print("." + m.getName() + "(");
      // print explicit arguments
      if (args != null)
      {
         for (int i = 0; i < args.length; i++)
         {
            System.out.print(args[i]);
            if (i < args.length - 1) System.out.print(", ");
         }
      }
      System.out.println(")");

      // invoke actual method
      return m.invoke(target, args);
   }
}

---

我测试了代码后，突然想到如果不用包装类Integer，直接用自定义类，然后实现接口Comparable，能不能也可以用二分查找函数来实现代理调用，下面是我的代码。

package wwydr.chapter6;/*

import java.lang.reflect.*;
import java.util.*;


public class ProxyTest
{
    public static void main(String[] args)
    {
        Object[] elements = new Object[1000];

        // fill elements with proxies for the integers 1 ... 1000
        for (int i = 0; i < elements.length; i++)
        {
//            Integer value = i + 1;
            int rAge = new Random().nextInt(65) + 1;
            Comparable value = new Employee32(rAge);
            InvocationHandler handler = new TraceHandler(value);
            ClassLoader loader=value.getClass().getClassLoader();
            Class [] interfaces=value.getClass().getInterfaces();
            Object proxy = Proxy.newProxyInstance(loader, interfaces , handler);
            elements[i] = proxy;
        }

        // construct a random integer
        Integer key = new Random().nextInt(65) + 1;

        // search for the key
        //binarySearch函数的返回值：
        // 如果key在数组中，则返回搜索值的索引；否则返回-1或者”-“(插入点)。插入点是索引键将要插入数组的那一点，即第一个大于该键的元素索引。
        int result = Arrays.binarySearch(elements, key);

        // print match if found
        if (result >= 0) System.out.println(elements[result]);
    }
}

/**
 * An invocation handler that prints out the method name and parameters, then
 * invokes the original method
 */
class TraceHandler implements InvocationHandler
{
    private Object target;
    
    /**
     * Constructs a TraceHandler
     * @param t the implicit parameter of the method call
     */
    public TraceHandler(Object t)
    {
        target = t;
    }

    @Override
    public Object invoke(Object proxy, Method m, Object[] args) throws Throwable
    {


        // print implicit argument
        System.out.print(target);
        // print method name
        System.out.print("^" + m.getName() + "(");
        // print explicit arguments
        if (args != null)
        {
            for (int i = 0; i < args.length; i++)
            {
                System.out.print(args[i]);
                if (i < args.length - 1) {
                    System.out.print(", ");
                }
            }
        }
        System.out.println(")");

        try {
            return m.invoke(target, args);
        } catch (InvocationTargetException e) {
            throw e.getCause();
        }
    }
}

class Employee32 implements Comparable<Employee32>
{
    private int age;

    @Override
    public int compareTo(Employee32 o) {
        return this.age - o.age;
    }

    public Employee32(int age) {
        this.age = age;
    }
}

---

相像是美好的，结果却很残酷，编译没有问题，运行时报错如下：

wwydr.chapter6.Employee32@5cad8086^compareTo(65)
Exception in thread "main" java.lang.ClassCastException: java.lang.Integer cannot be cast to wwydr.chapter6.Employee32
at wwydr.chapter6.Employee32.compareTo(ProxyTest.java:95)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at wwydr.chapter6.TraceHandler.invoke(ProxyTest.java:88)
at com.sun.proxy.$Proxy0.compareTo(Unknown Source)
at java.util.Arrays.binarySearch0(Arrays.java:2439)
at java.util.Arrays.binarySearch(Arrays.java:2379)
at wwydr.chapter6.ProxyTest.main(ProxyTest.java:41)

---

错误出现在这一句：return m.invoke(target, args);
args参数是Integer类型，target参数是Employee32类型，和我相像的两个都是Employee32类型不一致，我查了好多资料，居然都没有合适的解决办法，只能来此向各位请教，这究竟是什么原因，我该如何来解决这个问题.

Answer 1

用模板类型T