今天在學習動態代理,在調試的過程中出現了非法參數異常的問題,先看下異常:
Exception in thread "main" java.lang.IllegalArgumentException: object is not an instance of declaring class
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at com.test.Application.WorkHandler.invoke(WorkHandler.java:24)
at com.sun.proxy.$Proxy0.time(Unknown Source)
at com.test.Application.Test.main(Test.java:18)
後來發下原來是我把代理調用處理程序用調用真實對象方法的時候invoke方法的第一個參數寫成了method,應該寫真實的代理對象:
//錯誤的寫法
method.invoke(method, args);
正確的寫法如下:
package com.test.Application;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
public class WorkHandler implements InvocationHandler{
private Object obj;
public WorkHandler(Object obj) {
this.obj = obj;
}
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
System.out.println("before 動態代理...");
System.out.println(proxy.getClass().getName());
System.out.println(this.obj.getClass().getName());
if(method.getName().equals("work")) {
method.invoke(this.obj, args);
System.out.println("after 動態代理...");
return proxy;
} else {
System.out.println("after 動態代理...");
return method.invoke(this.obj, args);
}
}
}