JSP使用自定义标签防止表单重复提交的方法

package cn.itcast.apsliyuan.web.servlet;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class LoginServet extends HttpServlet {
  /**
   * 反序列化
   */
  private static final long serialVersionUID = 4960707156159691747L;
  @Override
  public void doPost(HttpServletRequest requset,
      HttpServletResponse response) throws ServletException, IOException {
    // 获得输入框中的值
    String token = requset.getParameter("tokenName");
    // 获得session中的值
    String sessionToken = (String) requset.getSession().getAttribute(
        "token");
    if (token.equals(sessionToken)) {
      response.getWriter().print("保存成功");
      requset.getSession().removeAttribute("token");//为了保证session中的值不重复，所以移除
    } else {
      response.getWriter().print("对不起不能重复提交");
    }
  }
}

package cn.itcast.apsliyuan.tag;
import java.io.IOException;
import java.util.UUID;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.TagSupport;
public class LoginTokenTag extends TagSupport{
  /**
   * 凡序列化
   */
  private static final long serialVersionUID = -1815168785364991254L;
  @Override
  public int doStartTag() throws JspException {
    // TODO Auto-generated method stub
    //得到uuid
    String uuid=UUID.randomUUID().toString().replace("-","");
    //得到session,pageContext 是域对象同样也是工具类
    pageContext.getSession().setAttribute("token",uuid);
    String html="input type='text' name='tokenName' readonly='readonly' value="+uuid+">";
    try {
      pageContext.getOut().print(html);
    } catch (IOException e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
    }
    return EVAL_BODY_INCLUDE;
  }
}

?xml version="1.0" encoding="UTF-8" ?>
taglib 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-jsptaglibrary_2_1.xsd"
  version="2.1">
  !-- 定义版本 -->
  tlib-version>1.0/tlib-version>
  !-- 定义名字 -->
  short-name>apsliyuan/short-name>
  !-- 定义uri -->
  uri>http://my.oschina.net/aps/uri>
  tag>
    name>loginTokenTag/name>
    tag-class>cn.itcast.apsliyuan.tag.LoginTokenTag/tag-class>
    body-content>JSP/body-content>
  /tag>
/taglib>

%@ page language="java" contentType="text/html; charset=UTF-8"
  pageEncoding="UTF-8"%>
  %@taglib uri="http://my.oschina.net/aps" prefix="aps" %>
  %@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
!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>index.jsp/title>
/head>
body>
  form action="${pageContext.request.contextPath}/server/Login" method="post">
    aps:loginTokenTag/>
    input type="submit" value="Login"/>
  /form>
/body>
/html>

package cn.itcast.apsliyuan.filter;
import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class UncodeFilter implements Filter {
  public void init(FilterConfig filterConfig) throws ServletException {
    // TODO Auto-generated method stub
    System.out.println("拦截完成");
  }
  public void doFilter(ServletRequest req, ServletResponse res,
      FilterChain chain) throws IOException, ServletException {
      HttpServletRequest request=(HttpServletRequest) req;
      HttpServletResponse response=(HttpServletResponse) res;
      request.setCharacterEncoding("UTF-8");
      response.setContentType("text/html;charset=UTF-8");
      chain.doFilter(request, response);
  }
  public void destroy() {
    // TODO Auto-generated method stub
  }
}

?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" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
  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>Tag/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>loginServlet/servlet-name>
    servlet-class>cn.itcast.apsliyuan.web.servlet.LoginServet/servlet-class>
  /servlet>
  servlet-mapping>
    servlet-name>loginServlet/servlet-name>
    url-pattern>/server/Login/url-pattern>
  /servlet-mapping>
  filter>
    filter-name>UncodeFilter/filter-name>
    filter-class>cn.itcast.apsliyuan.filter.UncodeFilter/filter-class>
  /filter>
  filter-mapping>
    filter-name>UncodeFilter/filter-name>
    url-pattern>/*/url-pattern>
  /filter-mapping>
/web-app>