Servlet的配置

今天接触了Servlet，Servlet 是一个 Java程序，是在服务器上运行以处理客户端请求并做出响应的程序Servlet是早期最初始的一个版本，慢慢形成JSP.介绍一下Servlet的配置。

案例：web项目WebRoot/WEB-INF/web.xml下

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5"
    xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
    http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">

  <!-- 注册servlet -->
  <servlet>
      <servlet-name>HelloServlet</servlet-name>
      <servlet-class>servlet.HelloServlet</servlet-class>
      <!-- 初始化参数:由当前servlet管理 -->
      <init-param>
          <param-name>name</param-name>
          <param-value>小明</param-value>
      </init-param>
  </servlet>

  <servlet>
    <description>This is the description of my J2EE component</description>
    <display-name>This is the display name of my J2EE component</display-name>
    <servlet-name>query</servlet-name>
    <servlet-class>servlet.query</servlet-class>
  </servlet>
    <servlet-mapping>
    <servlet-name>query</servlet-name>
    <url-pattern>/servlet/query</url-pattern>
  </servlet-mapping>

  <!-- 映射servlet -->
  <servlet-mapping>
      <servlet-name>HelloServlet</servlet-name>
      <url-pattern>/HelloServlet</url-pattern>
  </servlet-mapping>

  <!-- 上下文参数:由web容器管理 -->
  <context-param>
      <param-name>name</param-name>
      <param-value>admin</param-value>
  </context-param>

  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
</web-app>

JAVA代码：

package servlet;

import java.io.IOException;
import java.io.PrintWriter;

import javax.faces.application.Application;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import com.sun.corba.se.impl.interceptors.PINoOpHandlerImpl;

public class HelloServlet extends HttpServlet {

    /**
     * servlet生命周期
     *  1\实例化servlet（web容器实现）
     *    使用功能
     *    1、初始化工作;此方法只执行一次；在第一次访问sersvlet的时候执行(执行init（）方法体现)
     *    2、真正处理客户端请求(执行service()方法)
     *    输出响应信息
     *    3、关闭web容器；只执行一次；在web容器关闭的售后执行销毁servlet（执行destory()方法）
     */

    /* (non-Javadoc)
     * 重写父类初始化方法
     * @see javax.servlet.GenericServlet#init()
     */
    @Override
    public void init() throws ServletException {
        // TODO Auto-generated method stub
        System.out.println("servlet第一个执行的方法!!!");

        //得到servlet初始化
        System.out.println("初始化参数："+this.getServletConfig().getInitParameter("name"));

        //获取上下文参数
        System.out.println("上下文参数:"+this.getServletContext().getInitParameter("name"));
    }

    /* (non-Javadoc)
     * 以GET提交方式提交的请求调用该方法
     * 默认不指定提交方式的时候执行该方法
     * @see javax.servlet.http.HttpServlet#doGet(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)
     */
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        // TODO Auto-generated method stub

    }

    /* (non-Javadoc)
     * 以POST提交方式提交的请求调用该方法
     * @see javax.servlet.http.HttpServlet#doPost(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)
     */
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        // TODO Auto-generated method stub
        /**
         * 处理客户端的请求
         */
        System.out.println("执行service方法处理请求");

        //接收参数
        String username = request.getParameter("username");
        String password = request.getParameter("password");

        if(username.equals("admin") && password.equals("123456")){
            //相当于jsp页面的session
            HttpSession session = request.getSession();

            Application app = (Application) getServletContext();

            request.setAttribute("username", username);
            //跳转到成功页面
            request.getRequestDispatcher("/success.jsp").forward(request, response);
        }

        /**
         * 响应客户端请求
         */
        //告诉客户端怎么解释返回的内容
        response.setContentType("text/html;charset=utf-8");
        PrintWriter out = response.getWriter();
        out.print("<HTML>");
        out.print("<head><title>HelloServlet</title></head>");
        out.print("<body>HelloServlet第一个servlet诞生了!!!</body>");
        out.print("</HTML>");
        out.close();
    }

    /* (non-Javadoc)
     * servlet(销毁方法)
     * @see javax.servlet.GenericServlet#destroy()
     */
    @Override
    public void destroy() {
        // TODO Auto-generated method stub
        System.out.println("销毁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 query extends HttpServlet {

    /**
     * Constructor of the object.
     */
    public query() {
        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("  </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("  </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
    }

}

JSP代码：

<%@ 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>登录</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>
    <form action="HelloServlet" method="post">
        username:<input type="text" name="username" /><br/>
        password:<input type="password" name="password" /><br/>
        <input type="submit" />
    </form>
  </body>
</html>

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<%
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 ‘success.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>
       ${username } 登录成功<br>
  </body>
</html>