Servlet开发

Servlet引入：

百度百科详细servlet介绍；

重点概括:servlet运行在服务器上，处理用户请求。

我们使用response来获取一个写方法 PrintWriter out=response.getWriter(); out.print("要输出的信息") 输出值到页面中。

在HelloWorldServlet类中我们输出信息。

 package com.java1234.web;

 import java.io.IOException;

 import java.io.PrintWriter;

 import javax.servlet.ServletException;

 import javax.servlet.http.HttpServlet;

 import javax.servlet.http.HttpServletRequest;

 import javax.servlet.http.HttpServletResponse;

 public class HelloWorldServlet extends HttpServlet {

     /**

      *

      */

     private static final long serialVersionUID = 1L;

     @Override

     protected void doGet(HttpServletRequest request, HttpServletResponse response)

             throws ServletException, IOException {

         // TODO Auto-generated method stub

         this.doPost(request, response);

     }

     @Override

     protected void doPost(HttpServletRequest request, HttpServletResponse response)

             throws ServletException, IOException {

         // TODO Auto-generated method stub

         response.setCharacterEncoding("gbk");

         PrintWriter out = response.getWriter();

         out.print("<html>");

         out.print("<head><title>Servlet开发</title></head>");

         out.print("问候servlet tmd");

         out.print("</html>");

         out.close();

     }

 }

HelloWorldServlet.java

web.xml文件配置如下：

 <?xml version="1.0" encoding="UTF-8"?>

 <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">

   <display-name>HeadFristJspServlet05</display-name>

   <welcome-file-list>

     <welcome-file>index.html</welcome-file>

     <welcome-file>index.htm</welcome-file>

     <welcome-file>index.jsp</welcome-file>

     <welcome-file>default.html</welcome-file>

     <welcome-file>default.htm</welcome-file>

     <welcome-file>default.jsp</welcome-file>

   </welcome-file-list>

   <servlet>

     <servlet-name>HelloWorldServlet</servlet-name>

     <servlet-class>com.java1234.web.HelloWorldServlet</servlet-class>

   </servlet>

   <servlet-mapping>

     <servlet-name>HelloWorldServlet</servlet-name>

     <url-pattern>/helloWorld</url-pattern>

   </servlet-mapping>

 </web-app>

web.xml

这个配置知识我们在学习JSP九大内置对象----config的时候学习过配置的基本过程和访问的时候跳转次序。

Servlet的生命周期

简单的概括分为四步:servlet类加载--->实例化---->服务----->销毁

我们使用一个例子看一下完整的过程

首先建一个类LifeServlet.java

 package com.java1234.web;

 import java.io.IOException;

 import java.io.PrintWriter;

 import javax.servlet.ServletException;

 import javax.servlet.http.HttpServlet;

 import javax.servlet.http.HttpServletRequest;

 import javax.servlet.http.HttpServletResponse;

 public class LifeServlet extends HttpServlet{

     /**

      *

      */

     private static final long serialVersionUID = 1L;

     @Override

     protected void doGet(HttpServletRequest request, HttpServletResponse response)

             throws ServletException, IOException {

         // TODO Auto-generated method stub

         System.out.println("service服务开始啦");

         this.doPost(request,response);

     }

     @Override

     protected void doPost(HttpServletRequest request, HttpServletResponse response)

             throws ServletException, IOException {

         // TODO Auto-generated method stub

         PrintWriter out=response.getWriter();

         out.print("servcice提供服务");

         System.out.println("servcice提供服务！");

     }

     @Override

     public void destroy() {

         // TODO Auto-generated method stub

         System.out.println("销毁service");

     }

     @Override

     public void init() throws ServletException {

         // TODO Auto-generated method stub

         System.out.println("实例化service");

     }

 }

LifeServlet.java

web.xml配置如下：

 <?xml version="1.0" encoding="UTF-8"?>

 <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">

   <display-name>HeadFristJspServlet05</display-name>

   <welcome-file-list>

     <welcome-file>index.html</welcome-file>

     <welcome-file>index.htm</welcome-file>

     <welcome-file>index.jsp</welcome-file>

     <welcome-file>default.html</welcome-file>

     <welcome-file>default.htm</welcome-file>

     <welcome-file>default.jsp</welcome-file>

   </welcome-file-list>

   <servlet>

       <servlet-name>LifeServlet</servlet-name>

       <servlet-class>com.java1234.web.LifeServlet</servlet-class>

   </servlet>

   <servlet-mapping>

       <servlet-name>LifeServlet</servlet-name>

       <url-pattern>/life</url-pattern>

   </servlet-mapping>

 </web-app>

web.xml

当我们客户端访问life时

会出现：

当我们在一段时间内不使用或者访问的时候。容器认为servlet没啥鸟用了 所以就销毁。。。。

当然啦！init(初始化只会有一次)

这个我们可以从这里看到（我们在客户端请求了两次）：

客户端跳转VS服务器端跳转

1、在Servlet中获取session,application

2、客户端跳转 response.sendRedirect(“目标地址”)；

我们无法获取request的信息。

使用的类是

RedirectServlet.java 代码如下

 package com.java1234.web;

 import java.io.IOException;

 import javax.servlet.ServletContext;

 import javax.servlet.ServletException;

 import javax.servlet.http.HttpServlet;

 import javax.servlet.http.HttpServletRequest;

 import javax.servlet.http.HttpServletResponse;

 import javax.servlet.http.HttpSession;

 public class RedirectServlet extends HttpServlet{

     /**

      *

      */

     private static final long serialVersionUID = 1L;

     @Override

     protected void doGet(HttpServletRequest request, HttpServletResponse response)

             throws ServletException, IOException {

         // TODO Auto-generated method stub

         this.doPost(request, response);

     }

     @Override

     protected void doPost(HttpServletRequest request, HttpServletResponse response)

             throws ServletException, IOException {

         // TODO Auto-generated method stub

         request.setAttribute("requestKey", "request取值");//获取request

         HttpSession session=request.getSession();

         session.setAttribute("sessionKey", "session取值");//获取session

         ServletContext application=this.getServletContext();

         application.setAttribute("applicationKey", "applicaiton取值");//获取applicaiton

         response.sendRedirect("target-redirect.jsp");//客户端跳转/重定向

     }

 }

RedirectServlet.java

跳转的目标文件：

 <%@ page language="java" contentType="text/html; charset=utf-8"

     pageEncoding="utf-8"%>

 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

 <html>

 <head>

 <meta http-equiv="Content-Type" content="text/html; charset=utf-8">

 <title>target-redirect</title>

 </head>

 <body>

     <h1>Servlet取值</h1>

     <h6>request值：<%=request.getAttribute("requestKey") %></h6>

     <h6>session值：<%=session.getAttribute("sessionKey") %></h6>

     <h6>application值：<%=application.getAttribute("applicationKey") %></h6>

 </body>

 </html>

target-redirect.jsp

web.xml配置信息：

 <?xml version="1.0" encoding="UTF-8"?>

 <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">

   <display-name>HeadFristJspServlet05</display-name>

   <welcome-file-list>

     <welcome-file>index.html</welcome-file>

     <welcome-file>index.htm</welcome-file>

     <welcome-file>index.jsp</welcome-file>

     <welcome-file>default.html</welcome-file>

     <welcome-file>default.htm</welcome-file>

     <welcome-file>default.jsp</welcome-file>

   </welcome-file-list>

   <servlet>

     <servlet-name>HelloWorldServlet</servlet-name>

     <servlet-class>com.java1234.web.HelloWorldServlet</servlet-class>

   </servlet>

   <servlet-mapping>

     <servlet-name>HelloWorldServlet</servlet-name>

     <url-pattern>/helloWorld</url-pattern>

   </servlet-mapping>

   <servlet>

       <servlet-name>LifeServlet</servlet-name>

       <servlet-class>com.java1234.web.LifeServlet</servlet-class>

   </servlet>

   <servlet-mapping>

       <servlet-name>LifeServlet</servlet-name>

       <url-pattern>/life</url-pattern>

   </servlet-mapping>

   <servlet>

       <servlet-name>RedirectServlet</servlet-name>

       <servlet-class>com.java1234.web.RedirectServlet</servlet-class>

   </servlet>

   <servlet-mapping>

       <servlet-name>RedirectServlet</servlet-name>

       <url-pattern>/redirect</url-pattern>

   </servlet-mapping>

 </web-app>

web.xml

3、服务器跳转：使用的关键代码 RequestDispatcher rd=request.getRequestdispatcher(“目标地址”)；rd.forward(request,response);

文件为 ForwardServlet.java

 package com.java1234.web;

 import java.io.IOException;

 import javax.servlet.RequestDispatcher;

 import javax.servlet.ServletContext;

 import javax.servlet.ServletException;

 import javax.servlet.http.HttpServlet;

 import javax.servlet.http.HttpServletRequest;

 import javax.servlet.http.HttpServletResponse;

 import javax.servlet.http.HttpSession;

 public class ForwardServlet extends HttpServlet{

     /**

      *

      */

     private static final long serialVersionUID = 1L;

     @Override

     protected void doGet(HttpServletRequest request, HttpServletResponse response)

             throws ServletException, IOException {

         // TODO Auto-generated method stub

         this.doPost(request, response);

     }

     @Override

     protected void doPost(HttpServletRequest request, HttpServletResponse response)

             throws ServletException, IOException {

         // TODO Auto-generated method stub

         request.setAttribute("requestKey", "request取值");//获取request

         HttpSession session=request.getSession();

         session.setAttribute("sessionKey", "session取值");//获取session

         ServletContext application=this.getServletContext();

         application.setAttribute("applicationKey", "applicaiton取值");//获取applicaiton

         RequestDispatcher rd=request.getRequestDispatcher("target-redirect.jsp");

         rd.forward(request, response);

     }

 }

ForwardServlet.java

目标文件：

 <%@ page language="java" contentType="text/html; charset=utf-8"

     pageEncoding="utf-8"%>

 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

 <html>

 <head>

 <meta http-equiv="Content-Type" content="text/html; charset=utf-8">

 <title>target-redirect</title>

 </head>

 <body>

     <h1>Servlet取值服务器</h1>

     <h6>request值：<%=request.getAttribute("requestKey") %></h6>

     <h6>session值：<%=session.getAttribute("sessionKey") %></h6>

     <h6>application值：<%=application.getAttribute("applicationKey") %></h6>

 </body>

 </html>

target-redirect.jsp

配置如下：

 <?xml version="1.0" encoding="UTF-8"?>

 <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">

   <display-name>HeadFristJspServlet05</display-name>

   <welcome-file-list>

     <welcome-file>index.html</welcome-file>

     <welcome-file>index.htm</welcome-file>

     <welcome-file>index.jsp</welcome-file>

     <welcome-file>default.html</welcome-file>

     <welcome-file>default.htm</welcome-file>

     <welcome-file>default.jsp</welcome-file>

   </welcome-file-list>

   <servlet>

     <servlet-name>HelloWorldServlet</servlet-name>

     <servlet-class>com.java1234.web.HelloWorldServlet</servlet-class>

   </servlet>

   <servlet-mapping>

     <servlet-name>HelloWorldServlet</servlet-name>

     <url-pattern>/helloWorld</url-pattern>

   </servlet-mapping>

   <servlet>

       <servlet-name>LifeServlet</servlet-name>

       <servlet-class>com.java1234.web.LifeServlet</servlet-class>

   </servlet>

   <servlet-mapping>

       <servlet-name>LifeServlet</servlet-name>

       <url-pattern>/life</url-pattern>

   </servlet-mapping>

   <servlet>

       <servlet-name>RedirectServlet</servlet-name>

       <servlet-class>com.java1234.web.RedirectServlet</servlet-class>

   </servlet>

   <servlet-mapping>

       <servlet-name>RedirectServlet</servlet-name>

       <url-pattern>/redirect</url-pattern>

   </servlet-mapping>

   <servlet>

   <servlet-name>ForwardServlet</servlet-name>

       <servlet-class>com.java1234.web.ForwardServlet</servlet-class>

   </servlet>

   <servlet-mapping>

       <servlet-name>ForwardServlet</servlet-name>

       <url-pattern>/forward</url-pattern>

   </servlet-mapping>

 </web-app>

web.xml

结果为

客户端和服务器对比一目了然！！

最新文章

  1. MySql access denied for user错误
  2. WPF实现强大的动态公式计算
  3. eclipse注释模板及格式化模板导入步骤
  4. cinder backup
  5. mycat服务启动{管理模块启动过程}
  6. 代码研磨 Slim v3 (二)--app-&gt;run()
  7. Embedding Lua in C: Using Lua from inside C.
  8. H2嵌入式数据库的各种连接方式
  9. Forward reference vs. forward declaration
  10. 对于利用pca 和 cca 进行fmri激活区识别的理解
  11. 【Cocos2d-X开发学习笔记】第05期：渲染框架之布景层类（CCLayer）的使用
  12. linux视频学习7（ssh, linux启动过程分析，加解压缩，java网络编程）
  13. 201521123033《Java程序设计》第6周学习总结
  14. 使用git bash提交代码到github托管
  15. 【技巧】EasyUI分页组件pagination显示项控制
  16. kubernetes国内镜像拉取
  17. SharePoint自定义程序页面部署 不用重启IIS
  18. JDBC Like子句实例
  19. Java的Timer定时器
  20. BZOJ1500：[NOI2005]维修数列——题解

热门文章

  1. LN : leetcode 70 Climbing Stairs
  2. Xamarin.Forms跨平台开发入门-第二部分：深入解析
  3. Android图片压缩，不失真，上线项目
  4. spark on yarn模式下内存资源管理（笔记2）
  5. spark性能优化（包括优化原理及基本方法）
  6. 重构26-Remove Double Negative（去掉双重否定）
  7. InChatter系统之服务器开发（一）
  8. 建设一个能承受500万PV/每天的网站如果计算？
  9. node.js入门之三
  10. Linux Mint 教程