javaWeb实战项目图书管理系统--4.BaseServlet类中的知识盲点

红太狼 2024-03-23 11:32 29阅读 0赞

一、代码

package com.sxl.web.servlet;
    
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import java.io.IOException;
    import java.lang.invoke.VarHandle;
    import java.lang.reflect.Method;
    
    public class BaseServlet extends HttpServlet {
            private static final long serialVersionUID = 1L;
    
            protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{
            //设置编码
                request.setCharacterEncoding("UTF-8");
                response.setCharacterEncoding("UTF-8");
                response.setContentType("text/html;charset=utf-8");
              //获取方法名
                String m = request.getParameter("method");
               //获取方法类
                Class<? extends BaseServlet> clazz = this.getClass();
                //获取要执行的方法
                try {
                    Method method = clazz.getDeclaredMethod(m, HttpServletRequest.class, HttpServletResponse.class);
                    method.setAccessible(true);
                    method.invoke(this,request,response);
                } catch (Exception e) {
                    e.printStackTrace();
                    System.out.println("BaseServlet异常处理");
                }
    
            }
    
    }

二、代码盲点分析

//获取方法类
     Class<? extends BaseServlet> clazz = this.getClass();

解析：通过反射方法中this.getClass()获得方法类

//获取要执行的方法
    try {
        Method method = clazz.getDeclaredMethod(m, HttpServletRequest.class, HttpServletResponse.class);
        method.setAccessible(true);
        method.invoke(this,request,response);

解析：① Method method = clazz.getDeclaredMethod(String name, Class<?>… parameterTypes) **获取本类中的所有方法**

②method.setAccessible(flag)//默认的flag为false。**当flag为true表明屏蔽Java、**

**语言的访问检查，时期对象中的私有属性也可以被查询和设置**

③调用方法（`invoke(Object obj, Object... args)`）