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JavaWeb常见错误
1.<a href="http://www.mamicode.com/customerServlet?method=add">Add</a> 这里method=add不能有空格,否则报错(空指针异常)
1 <%@ page language="java" contentType="text/html; charset=ISO-8859-1" 2 pageEncoding="ISO-8859-1"%> 3 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> 4 <html> 5 <head> 6 <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> 7 <title>Insert title here</title> 8 </head> 9 <body>10 <a href="http://www.mamicode.com/customerServlet?method=add">Add</a>11 <br>12 <br>13 14 <a href="http://www.mamicode.com/customerServlet?method=query">Query</a>15 <br>16 <br>17 18 <a href="http://www.mamicode.com/customerServlet?method=delete">Delete</a>19 <br>20 <br>21 22 </body>23 </html>
1 package com.ouyang.dao; 2 3 import java.io.IOException; 4 5 import javax.servlet.ServletException; 6 import javax.servlet.annotation.WebServlet; 7 import javax.servlet.http.HttpServlet; 8 import javax.servlet.http.HttpServletRequest; 9 import javax.servlet.http.HttpServletResponse;10 11 @WebServlet("/customerServlet")12 public class CustomerServlet extends HttpServlet {13 private static final long serialVersionUID = 1L;14 15 protected void doGet(HttpServletRequest request,16 HttpServletResponse response) throws ServletException, IOException {17 doPost(request, response);18 }19 20 protected void doPost(HttpServletRequest request,21 HttpServletResponse response) throws ServletException, IOException {22 String method = request.getParameter("method");23 24 switch (method) {25 case "add":26 add(request, response);27 break;28 case "query":29 query(request, response);30 break;31 case "delete":32 delete(request, response);33 break;34 35 }36 37 }38 39 private void delete(HttpServletRequest request, HttpServletResponse response)40 throws ServletException, IOException {41 System.out.println("delete");42 }43 44 private void query(HttpServletRequest request, HttpServletResponse response)45 throws ServletException, IOException {46 System.out.println("query");47 }48 49 private void add(HttpServletRequest request, HttpServletResponse response)50 throws ServletException, IOException {51 System.out.println("add");52 53 }54 55 }
2.url-pattern 中在建立Servlet时前面不应该加"/".否则会报错
JavaWeb常见错误
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