javaWeb_BaseServlet --对于servlet的改写, 使得servlet更加优雅,类似于springmvc等

目的 : 实现BaseServlet, 实现对于servlet的优雅编写, 减少重复代码的出现

需要解决的问题 : 

设计思路 : 继承HttpServlet, 重写service方法. 原本操作是:重写doGet与重写doPost(这两个函数原本由service调用)

实际代码 : 

　　1. BaseServlet的实现 : 

 1 package com.theangryz.servlet;
 2 
 3 import javax.servlet.ServletException;
 4 import javax.servlet.http.HttpServlet;
 5 import javax.servlet.http.HttpServletRequest;
 6 import javax.servlet.http.HttpServletResponse;
 7 import java.io.IOException;
 8 import java.lang.reflect.Method;
 9 
10 public class BaseServlet extends HttpServlet {
11     @Override
12     protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
13         Class clazz = this.getClass();
14         String methodName = req.getParameter("method");
15         if (methodName == null || methodName.trim().isEmpty()){
16             throw new RuntimeException("没有输入method参数");
17         }
18         Method method = null;
19         try{
20             method = clazz.getDeclaredMethod(methodName, HttpServletRequest.class, HttpServletResponse.class);
21         }catch (Exception e){
22             throw new RuntimeException("你调用的方法" + methodName + "不存在");
23         }
24         String str = null;
25         try{
26             str = (String) method.invoke(this, req, resp);
27         }catch(Exception e){
28             throw new RuntimeException("方法执行出错");
29         }
30         if (str == null || str.trim().isEmpty()){
31             return ;
32         }
33         if (str.contains(":")){
34             int index = str.indexOf(":");
35             String prefix = str.substring(0, index);
36             String suffix = str.substring(index+1);
37             if (prefix.equalsIgnoreCase("f")){     //转发
38                 req.getRequestDispatcher(suffix).forward(req, resp);
39             }else if (prefix.equalsIgnoreCase("r")){   //重定向
40                 resp.sendRedirect(req.getContextPath() + suffix);
41             }else{
42                 throw new RuntimeException("当前版本不支持该前缀 : " + prefix);
43             }
44         }else{  //默认转发
45             req.getRequestDispatcher(str).forward(req, resp);
46         }
47     }
48 }

　　2. AServlet的实现(该AServlet用于测试BaseServlet)

 1 package com.theangryz.servlet;
 2 
 3 import javax.servlet.ServletException;
 4 import javax.servlet.http.HttpServletRequest;
 5 import javax.servlet.http.HttpServletResponse;
 6 import java.io.IOException;
 7 
 8 public class AServlet extends BaseServlet{
 9     protected String addUser(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
10 
11         response.getWriter().print("addUser执行结束了");
12         return "/show.jsp";
13     }
14     protected String func1(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
15         System.out.println("func1");
16         return "f:/show.jsp";
17     }
18     protected String func2(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
19         System.out.println("func1");
20         return "r:/show.jsp";
21     }
22     protected String func3(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
23         System.out.println("func1");
24         return null;
25     }
26 }

实际编写中遇到的问题 : 

　　1. 程序在执行 clazz.getMethod(methodName, HttpServletRequest.class, HttpServletResponse.class)一直抛出异常(methodName是正确的前提下).

　　　　解决 : getMethod方法反射只能获取public的方法与继承得来的public方法. 但是在AServlet中方法的访问修饰为protected, 所以即使methodName是正确的, getMethod还是没有办法反射得到protected的方法. 所以程序使用了getDeclaredMethod()方法, 该方法可以得到除了继承得来的方法之外的所有方法.

标签：HttpServletRequest,BaseServlet,String,HttpServletResponse,str,import,servlet,jav
来源： https://www.cnblogs.com/gogotao/p/11965679.html