Servlet基础

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最新推荐文章于 2024-10-22 15:28:12 发布

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本文介绍了Servlet的基本概念，包括其定义、生命周期及实现方式，并通过手写和使用开发工具自动生成的两个Servlet示例进行详细说明。

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Servlet理解
① Servlet就是JAVA 类
② Servlet是一个继承HttpServlet类的类
③　这个在服务器端运行，用以处理客户端的请求
Servlet生命周期
–Servlet生命周期就是指创建Servlet实例后，存在的时间以及何时销毁的整个过程．
–Servlet生命周期有三个方法
　　init()方法：
　　service()方法：Dispatches client requests to the protected service method　
　　destroy()方法：Called by the servlet container to indicate to a servlet that the servlet is being taken out of service.
Servlet例子

JSP
两种servlet 生成方法，一种是手写servlet，需要手动配置xml文件，一种是myeclipse自动生成的servlet

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">

    <title>My JSP 'index.jsp' starting page</title>
    <meta http-equiv="pragma" content="no-cache">
    <meta http-equiv="cache-control" content="no-cache">
    <meta http-equiv="expires" content="0">    
    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
    <meta http-equiv="description" content="This is my page">
    <!--
    <link rel="stylesheet" type="text/css" href="styles.css">
    -->
  </head>

  <body>
    This is my JSP page. <br>
    <a href="servlet/HelloServlet">GET方式请求HelloServlet</a>
    <form action="servlet/HelloServlet" method="post">
        <input type="submit" value="Post 提交"/>
    </form>
    <a href="servlet/HelloServlet2">GET方式请求HelloServlet2</a>
    <form action="servlet/HelloServlet2" method="post">
        <input type="submit" value="Post 提交"/>
    </form>
  </body>
</html>

HelloServlet.java类，手写的Servlet

package servlet;

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 HelloServlet extends HttpServlet {

    /* (non-Javadoc)
     * @see javax.servlet.http.HttpServlet#doGet(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)
     */
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // TODO Auto-generated method stub

        System.out.println("处理get请求");
        PrintWriter out = resp.getWriter();
        resp.setContentType("text/html;charset=utf-8");
        out.println("<strong>处理get请求 Servlet!</strong><br>");
    }

    /* (non-Javadoc)
     * @see javax.servlet.http.HttpServlet#doPost(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)
     */
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // TODO Auto-generated method stub
        //super.doPost(req, resp);
        System.out.println("处理post请求");
        PrintWriter out = resp.getWriter();
        resp.setContentType("text/html;charset=utf-8");
        out.println("<strong>处理post请求Hello Servlet!</strong><br>");
    }

}

配置文件

<servlet>
    <servlet-name>HelloServlet</servlet-name>//servlet的名字
    <servlet-class>servlet.HelloServlet</servlet-class>//所在的类，注意中间用点来连接
  </servlet>
  <servlet-mapping>
    <servlet-name>HelloServlet</servlet-name>
    <url-pattern>/servlet/HelloServlet</url-pattern>//url的跳转的地址
  </servlet-mapping>

HelloServlet2.java类，自动生成的Servlet

package servlet;

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 HelloServlet2 extends HttpServlet {

    /**
         * Constructor of the object.
         */
    public HelloServlet2() {
        super();
    }

    /**
         * Destruction of the servlet. <br>
         */
    public void destroy() {
        super.destroy(); // Just puts "destroy" string in log
        // Put your code here
    }

    /**
         * The doGet method of the servlet. <br>
         *
         * This method is called when a form has its tag value method equals to get.
         * 
         * @param request the request send by the client to the server
         * @param response the response send by the server to the client
         * @throws ServletException if an error occurred
         * @throws IOException if an error occurred
         */
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        out.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");
        out.println("<HTML>");
        out.println("  <HEAD><TITLE>A Servlet</TITLE></HEAD>");
        out.println("  <BODY>");
        out.print("    This is ");
        out.print(this.getClass());
        out.println(", using the GET method");
        out.println("<strong>myeclipse 生成servlet</strong>");
        out.println("  </BODY>");
        out.println("</HTML>");
        out.flush();
        out.close();
    }

    /**
         * The doPost method of the servlet. <br>
         *
         * This method is called when a form has its tag value method equals to post.
         * 
         * @param request the request send by the client to the server
         * @param response the response send by the server to the client
         * @throws ServletException if an error occurred
         * @throws IOException if an error occurred
         */
    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        out.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");
        out.println("<HTML>");
        out.println("  <HEAD><TITLE>A Servlet</TITLE></HEAD>");
        out.println("  <BODY>");
        out.print("    This is ");
        out.print(this.getClass());
        out.println(", using the POST method");
        out.println("<strong>myeclipse 生成servlet</strong>");
        out.println("  </BODY>");
        out.println("</HTML>");
        out.flush();
        out.close();
    }

    /**
         * Initialization of the servlet. <br>
         *
         * @throws ServletException if an error occurs
         */
    public void init() throws ServletException {
        // Put your code here
    }

}