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  • Servlet编程笔记

    使用纯文本方式的编程方式略过。

    下面利用MyEclipse和Dreamweaver这两个开发工具，设计一张调查统计，并显示调查结果。

    相关知识点：Servlet获取表单参数

    1.新建一个Web工程。

    clip_image001

    2.在Dreamweaver中，新建一个html页面，叫做survey.html。

    image

    右边红框内，是表示这些内容在form表单中。

    设置各自input控件的名字。

    同一组空间（如年龄）的name设置为相同。

    注意：我这个版本的Dreamweaver中，在form属性中，会自动添加enctype= "multipart/form-data " 属性，这会导致后面出现严重错误，我排查了很久才找到。后面错误为：request.getParameter(name)这个方法中，获取的参数永远为null值。

    HTML代码如下：

       1: <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
       2: <html xmlns="http://www.w3.org/1999/xhtml">
       3: <head>
       4: <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
       5: <title>无标题文档</title>
       6: </head>
       7:  
       8: <body>
       9: <p>网络调查表</p>
      10: <form action="webProject2/servlet/survey" method="post" enctype="multipart/form-data" name="form1" id="form1">
      11:   <table width="504" border="0">
      12:     <tr>
      13:       <td width="138">姓名：</td>
      14:       <td width="356"><label for="name"></label>
      15:       <input name="name" type="text" id="name" size="20" /></td>
      16:     </tr>
      17:     <tr>
      18:       <td>Email：</td>
      19:       <td><label for="email"></label>
      20:       <input name="email" type="text" id="email" size="40" /></td>
      21:     </tr>
      22:     <tr>
      23:       <td>年龄：</td>
      24:       <td><input type="radio" name="age" id="radio" value="18" />
      25:         小于18
      26:           <input name="age" type="radio" id="radio2" value="18-40" checked="checked" />
      27:         <label for="age"></label>
      28:         18-40
      29:         <input type="radio" name="age" id="radio3" value="40" />
      30:         <label for="age">大于40</label></td>
      31:     </tr>
      32:     <tr>
      33:       <td>编程时间：</td>
      34:       <td><label for="code"></label>
      35:         <select name="code" id="code">
      36:           <option value="never">不编程</option>
      37:           <option value="6" selected="selected">小于6个月</option>
      38:           <option value="6-12">6到12个月</option>
      39:           <option value="12-24">12-24个月</option>
      40:           <option value="24">大于24个月</option>
      41:       </select></td>
      42:     </tr>
      43:     <tr>
      44:       <td>操作系统：</td>
      45:       <td><label for="system"></label>
      46:         <select name="system" size="4" multiple="multiple" id="system">
      47:           <option value="winxp" selected="selected">Windows XP</option>
      48:           <option value="win7">Windows 7</option>
      49:           <option value="maxos">Max OS</option>
      50:           <option value="liunx">Liunx</option>
      51:       </select></td>
      52:     </tr>
      53:     <tr>
      54:       <td>编程语言：</td>
      55:       <td><input name="language" type="checkbox" id="language" value="java" />
      56:         Java
      57:       <label for="language"></label>
      58:       <input name="language" type="checkbox" id="language" value="c" />
      59:       C
      60:       <label for="language"></label>
      61:       <input name="language" type="checkbox" id="language" value="c++" />
      62:       C++
      63:       <label for="language"></label>
      64:       <input name="language" type="checkbox" id="language" value="cshape" />
      65:       C#
      66:       <label for="language"></label>
      67:       <input name="language" type="checkbox" id="language" value="vb" />
      68:       <label for="language">VB</label></td>
      69:     </tr>
      70:     <tr>
      71:       <td>建议：</td>
      72:       <td><label for="sugestion"></label>
      73:         <label for="comment"></label>
      74:       <textarea name="comment" id="comment" cols="45" rows="4"></textarea></td>
      75:     </tr>
      76:     <tr>
      77:       <td><input type="submit" name="submit" id="submit" value="提交" /></td>
      78:       <td><input type="reset" name="reset" id="reset" value="重置" /></td>
      79:     </tr>
      80:     <tr>
      81:       <td>&nbsp;</td>
      82:       <td><label for="textfield"></label></td>
      83:     </tr>
      84:     <tr>
      85:       <td>&nbsp;</td>
      86:       <td>&nbsp;</td>
      87:     </tr>
      88:   </table>
      89: </form>
      90: <p>&nbsp;</p>
      91: </body>
      92: </html>

    3.在webProject2中添加Servlet类，并选择重构doPost()和doGet()方法。

    注意点：

    1.将输入的html设置为utf-8编码。

       1: response.setContentType("text/html;charset=utf-8");

    2.将获取的request设置为utf-8编码

       1: request.setCharacterEncoding("utf-8");

    3.使用request.getParameter(name)方法获取单个值的控件的值。

       1: request.getParameter("age")

    4.使用request.getParameterValues(name)方法获取多个值的空间的值

       1: request.getParameterValues("system");

    5.对用户输入框的内容进行内容过滤，防止js代码并使换行生效。

    防止js代码：对<,>,’,”, ，&等进行替换。

       1: value = value.replace("&", "&amp;");
       2: value = value.replace("<", "&lt;");
       3: value = value.replace(">", "&gt;");
       4: value = value.replace(" ", "&nbsp;");
       5: value = value.replace("'", "&#39;");
       6: value = value.replace("\"", "&quot;");

    使得换行生效：将\n换位<br />

       1: value = value.replace("\n", "<br />");

    6.结尾处关闭数据流（系统已自动生成）：

       1: out.flush();
       2: out.close();

    7.防止多选框未作选择的错误，加一个异常处理。

       1: try {
       2:         String[] language = request.getParameterValues("language");
       3:         for (String s : language) {
       4:             out.println("<li>" + s + "</li>");
       5:         }
       6:     } catch (Exception e) {
       7:         out.println("没有选择编程语言<br />");
       8:     }

    参考代码：

       1: package jacob.practice;
       2:  
       3: import java.io.IOException;
       4: import java.io.PrintWriter;
       5: import java.util.Enumeration;
       6:  
       7: import javax.servlet.ServletException;
       8: import javax.servlet.http.HttpServlet;
       9: import javax.servlet.http.HttpServletRequest;
      10: import javax.servlet.http.HttpServletResponse;
      11:  
      12: public class SurveyServlet extends HttpServlet {
      13:  
      14:     /**
      15:      * The doGet method of the servlet. <br>
      16:      * 
      17:      * This method is called when a form has its tag value method equals to get.
      18:      * 
      19:      * @param request
      20:      *            the request send by the client to the server
      21:      * @param response
      22:      *            the response send by the server to the client
      23:      * @throws ServletException
      24:      *             if an error occurred
      25:      * @throws IOException
      26:      *             if an error occurred
      27:      */
      28:     public void doGet(HttpServletRequest request, HttpServletResponse response)
      29:             throws ServletException, IOException {
      30:  
      31:         doPost(request, response);
      32:     }
      33:  
      34:     /**
      35:      * The doPost method of the servlet. <br>
      36:      * 
      37:      * This method is called when a form has its tag value method equals to
      38:      * post.
      39:      * 
      40:      * @param request
      41:      *            the request send by the client to the server
      42:      * @param response
      43:      *            the response send by the server to the client
      44:      * @throws ServletException
      45:      *             if an error occurred
      46:      * @throws IOException
      47:      *             if an error occurred
      48:      */
      49:     public void doPost(HttpServletRequest request, HttpServletResponse response)
      50:             throws ServletException, IOException {
      51:  
      52:         response.setContentType("text/html;charset=utf-8");
      53:         PrintWriter out = response.getWriter();
      54:         out.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");
      55:         out.println("<HTML>");
      56:         out.println("  <HEAD><TITLE>A Servlet</TITLE></HEAD>");
      57:         out.println("  <BODY>");
      58:         request.setCharacterEncoding("utf-8");
      59:         out.println("姓名：" + filterHtml(request.getParameter("name")) + "<br />");
      60:         out.println("Email：" + filterHtml(request.getParameter("email"))
      61:                 + "<br />");
      62:         out.println("年龄：" + request.getParameter("age") + "<br />");
      63:         out.println("编程时间：" + request.getParameter("code") + "<br />");
      64:         out.println("操作系统：<ul>");
      65:         String[] os = request.getParameterValues("system");
      66:         for (String s : os) {
      67:             out.println("<li>" + s + "</li>");
      68:         }
      69:         out.println("</ul><br />");
      70:         out.println("编程语言：<ul>");
      71:         try {
      72:             String[] language = request.getParameterValues("language");
      73:             for (String s : language) {
      74:                 out.println("<li>" + s + "</li>");
      75:             }
      76:         } catch (Exception e) {
      77:             out.println("没有选择编程语言<br />");
      78:         }
      79:  
      80:         out.println("</ul><br />");
      81:         out.println("建议：" + filterHtml(request.getParameter("comment"))
      82:                 + "<br />");
      83:         out.println("  </BODY>");
      84:         out.println("</HTML>");
      85:         out.flush();
      86:         out.close();
      87:     }
      88:  
      89:     public String filterHtml(String value) {
      90:         value = value.replace("&", "&amp;");
      91:         value = value.replace("<", "&lt;");
      92:         value = value.replace(">", "&gt;");
      93:         value = value.replace(" ", "&nbsp;");
      94:         value = value.replace("'", "&#39;");
      95:         value = value.replace("\"", "&quot;");
      96:         value = value.replace("\n", "<br />");
      97:         return value;
      98:  
      99:     }
     100:  
     101: }

    4.部署。

    启动Tomcat并部署。

    5.运行。

    在浏览器中输入http://localhost/webProject2/servlet/survey.html（这个根据自己设置的路径，参见web.xml这个文件）。

    HTML页面：

    image

    统计界面：

    image
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  • 原文地址：https://www.cnblogs.com/XuYankang/p/2451672.html
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