Servlet中init()重写时出现NullPointerException

最新推荐文章于 2022-05-04 16:42:43 发布

原创最新推荐文章于 2022-05-04 16:42:43 发布 · 347 阅读

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文章标签：

#init

本文深入解析Servlet3.0的重要特性，包括注解配置、初始化参数的使用及Servlet生命周期方法。通过具体代码示例，展示如何创建、初始化、处理HTTP请求及销毁Servlet实例。

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package cn.saifei.servlet;

import java.io.IOException;

import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebInitParam;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet(value="/Servlet30Project",loadOnStartup=1,initParams= {@WebInitParam(name="servletname", value="servletvalue")})
public class Servlet30Project extends HttpServlet {

   @Override
   public void init(ServletConfig config) throws ServletException {
       super.init(config);//没有这句会出现NullPointerException异常
       System.out.println("init3.0....");
       String value = getInitParameter("servletname");
       System.out.println(value);

   }
   protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
       System.out.println("dpGet30.......");
   }

   protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
       System.out.println("doPost30....");
   }
   @Override
   public void destroy() {
       System.out.println("destroy3.0....");
   }

}