java - 使用反射 api 时抛出 NoSuchMethodException

Question

我正在使用反射 api 从类的实例调用方法。一切正常，我一步一步地遵循了许多教程和官方 oracle 文档，但它抛出 NoSuchMethodException。这是我的代码:

// Part of the main class
    Class[] argTypes = new Class[2];
    argTypes[0] = HttpServletRequest.getClass();
    argTypes[1] = HttpServletResponse.getClass();

    Object[] args = new Object[2];
    args[0] = request;
    args[1] = response;

    try {
        Class<?> cls = Class.forName("x.xx.xxx.Default");
        Object object = cls.newInstance();
        Method method = cls.getDeclaredMethod("index", argTypes);
        method.invoke(object, args);
    } catch (Exception exception) { // for simplicity of the question, I replaced all exception types with Exception
        exception.printStackTrace();
    }

// End of the main class
    // class x.xx.xxx.Default

    public class Default {
        public void index(HttpServletRequest request, HttpServletResponse response) {
            try {
                PrintWriter writer = response.getWriter();
                writer.println("Welcome");
            } catch (IOException exception) {
                System.err.println(exception);
            }
        }
    }

这是我在异常发生时给出的exception的描述

java.lang.NoSuchMethodException: x.xx.xxx.Default.index(org.apache.catalina.connector.RequestFacade, org.apache.catalina.connector.ResponseFacade)

Answer 1

我相信您需要传递静态类而不是运行时的类。

Class[] argTypes = new Class[2];
argTypes[0] = HttpServletRequest.class;
argTypes[1] = HttpServletResponse.class;