Java EE WEB工程师培训-JDBC+Servlet+JSP整合开发之11.Servlet简介

–为什么需要动态创建Web页面？
–Servlet 的功能
–Servlet 相对“传统” CGI的优势
–Servlet 的相关类和接口
–Servlet 实例
• “HelloWorld” Servlet

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• 为什么需要动态创建Web页面？
–Web页面基于用户提交的数据
• 例如，搜索引擎的结果和在线商店的订单确认信息
–Web 页面的数据频繁改变
• 例如，天气预报和新闻头条
–页面信息来自数据库
• 例如，电子商务网站的每日销售商品的价格清单

• Servlet 的功能
–读取客户端发来的显示信息（表单数据）
–读取客户端发来的隐式信息（请求头信息）
–生成相应结果
–发送显示信息给客户端（HTML）
–发送隐式数据到客户端（状态码和响应头信息）

• Servlet 相对“传统”CGI的优势
–效率高
• 线程取代操作系统的进程
–方便
• 大量高级工具类
–功能强大
• 共享数据，数据持久性
–轻便
• 可以运行在所有操作系统上
–廉价
• 有大量的免费或价格较低的服务器
–安全
• 没有缓存溢出问题
–主流

• Servlet 的相关类和接口
– 包结构
• javax.servlet
• javax.servlet.http

– Servlet 接口
• public void init(ServletConfig config) throws ServletException
• public ServletConfig getServletConfig()
• public void service(ServletRequest req,ServletResponse res) throws
ServletException,java.io.IOException
• public java.lang.String getServletInfo()
• public void destroy()

– ServletConfig
• public java.lang.String getServletName()
• public java.lang.String getInitParameter(java.lang.String name)
• public java.util.Enumeration getInitParameterNames()

– ServletContext
• public ServletContext getContext(java.lang.String uripath)
• public RequestDispatcher getRequestDispatcher(java.lang.String path)
• public void log(java.lang.String msg)
• public java.lang.String getRealPath(java.lang.String path)
• public java.lang.String getInitParameter(java.lang.String name)
• public java.lang.Object getAttribute(java.lang.String name)

– ServletRequest
• public void setAttribute(java.lang.String name,java.lang.Object o)
• public void setCharacterEncoding(java.lang.String env) throws java.io.UnsupportedEncodingException
• public java.lang.String getParameter(java.lang.String name)
• public java.lang.String[] getParameterValues(java.lang.String name)

– ServletResponse
• public ServletOutputStream getOutputStream() hrows java.io.IOException
• public java.io.PrintWriter getWriter() throws java.io.IOException

– GenericServlet
• public abstract class GenericServlet
• extends java.lang.Object
• implements Servlet, ServletConfig, java.io.Serializable

– HttpServlet
• public abstract class HttpServlet
• extends GenericServlet
• implements java.io.Serializable

– HttpServletRequest
• public interface HttpServletRequest
• extends ServletRequest

– HttpServletResponse
• public interface HttpServletResponse
• extends ServletResponse

– HttpSession
• public void setAttribute(java.lang.String name,java.lang.Object value)
• public void invalidate()

• Servlet 实例
–“HelloWorld” Servlet
• 创建一个HelloWorldServlet类
–编写一个类“HelloWorldServlet”继承HttpServlet
–覆盖HttpServlet中的doGet方法
–在doGet方法中将“Hello World Servlet”输出

• 声明、映射Servlet
–声明Servlet

–映射Servlet

• 调用Servlet方式
–URL
–提交表单
–超级连接
–JavaScript脚本 

• 运行结果

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URL调用Servlet方法

创建一个MyServlet类

MyServlet.java

package com.michael.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 MyServlet extends HttpServlet{    

        @Override    
        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {    
                PrintWriter out = response.getWriter();    
                out.println("My blog is http://redking.blog.51cto.com");    
        }    

        @Override    
        protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {    
                doGet(request,response);    
        }    
}

申明、映射Servlet

web.xml

<?xml version="1.0" encoding="UTF-8"?>    
<web-app version="2.4"    
        xmlns="http://java.sun.com/xml/ns/j2ee"    
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"    
        xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee    
http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">    

        <!-- 申明Servlet -->    
        <servlet>    
                <servlet-name>王乾De技术Blog[爱生活，爱学习]</servlet-name>    
                <servlet-class>com.michael.servlet.MyServlet</servlet-class>    
        </servlet>    
        <!-- 映射Servlet -->    
        <servlet-mapping>    
                <servlet-name>王乾De技术Blog[爱生活，爱学习]</servlet-name>    
                <url-pattern>/servlet/michael.do</url-pattern>    
        </servlet-mapping>    
</web-app>

测试

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提交表单调用Servlet方法

增加一个login.html页面

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">    
<html>    
    <head>    
        <title>login.html</title>    
        <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">    
        <meta http-equiv="description" content="this is my page">    
        <meta http-equiv="content-type" content="text/html; charset=gbk">    
        <!--<link rel="stylesheet" type="text/css" href="./styles.css">-->    

    </head>    
    <body>    
        <form action="/Servlet_Info/servlet/michael.do" method="post">    
            <table border="0">    
                <tr>    
                    <td>帐号:</td>    
                    <td><input type="text" name="user" id="login"></td>    
                </tr>    
                <tr>    
                    <td>密码:</td>    
                    <td><input type="password" name="password" id="password"></td>    
                </tr>    
                <tr>    
                    <td colspan="2" align="center"><input type="submit" value="登录"></td>    
                </tr>    
            </table>    
        </form>    
    </body>    
</html>

测试

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超链接调用Servlet方法

测试

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JavaScript脚本调用Servlet方式

login.html

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">    
<html>    
    <head>    
        <title>login.html</title>    
        <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">    
        <meta http-equiv="description" content="this is my page">    
        <meta http-equiv="content-type" content="text/html; charset=gbk">    
        <!--<link rel="stylesheet" type="text/css" href="./styles.css">-->    

        <script type="text/javascript">    
                function invoke(){    
                        var myForm = document.getElementById("michaelForm");    
                        myForm.action = "/Servlet_Info/servlet/michael.do";    
                        myForm.submit();    
                }    
        </script>    
    </head>    
    <body>    
            <a href="/Servlet_Info/servlet/michael.do">click me!!!</a>    
        <form id="michaelForm" action="/Servlet_Info/servlet/michael.do" method="post">    
            <table border="0">    
                <tr>    
                    <td>帐号:</td>    
                    <td><input type="text" name="user" id="login"></td>    
                </tr>    
                <tr>    
                    <td>密码:</td>    
                    <td><input type="password" name="password" id="password"></td>    
                </tr>    
                <tr>    
                    <td colspan="2" align="center"><input type="submit" value="登录"></td>    
                    <input type="button" value="JS Submit" onclick="invoke()"><br><br>    
                </tr>    
            </table>    
        </form>    
    </body>    
</html>

测试

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