JSP uses a custom label to prevent forms from repeating submissions _jsp programming

The example in this article describes how JSP uses custom labels to prevent forms from repeating submissions. Share to everyone for your reference. Specifically as follows:

1. Preparation of Servelt:

 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 {/** * deserialization/private static final long Serialversionuid = 496070
  7156159691747L; @Override public void DoPost (HttpServletRequest requset, httpservletresponse response) throws Servletexception, IO
    Exception {//Get the value in the input box String token = requset.getparameter ("Tokenname");
    Gets the value in the session string Sessiontoken = (string) requset.getsession (). getattribute ("token");
      if (Token.equals (Sessiontoken)) {Response.getwriter (). Print ("saved successfully"); Requset.getsession (). RemoveAttribute ("token");//To ensure that the values in the session do not repeat, remove} else {Response.getwriter (). Print ("I'm sorry.
    can be repeated "); }
  }
}

2. Write a custom Label class:

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{
  /**
   * where serialization/
  private static final long Serialversionuid = -1815168785364991254l;
  @Override public
  int doStartTag () throws Jspexception {
    //TODO auto-generated a stub
    //Get UUID
    String Uuid=uuid.randomuuid (). toString (). Replace ("-", "");
    Getting Session,pagecontext is a domain object as well as a tool class
    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
  }
}

3. Preparation of X.TLD documents:

<?xml version= "1.0" encoding= "UTF-8"?> <taglib xmlns= "Http://java.sun.com/xml/ns/javaee"
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 ">
  <!--defined version-->
  < tlib-version>1.0</tlib-version>
  <!--definition name-->
  <short-name>apsliyuan</short-name >
  <!--definition 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>

4. The code in the JSP:

<%@ 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" >
 
 

5. Prevent garbled Interceptor:

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 ("Intercept complete"); public void Dofilter (ServletRequest req, servletresponse Res, Filterchain chain) throws IOException, Servletexce
      ption {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}}

 

Configuration in

6. Web.xml:

<?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>i Ndex.html</welcome-file> <welcome-file>index.htm</welcome-file> <welcome-file>index.jsp& Lt;/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> &L T;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>

I hope this article will help you with your JSP programming.