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JSP Using Custom Labels to Prevent Form Duplicate Submissions

  • 2021-07-24 11:34:10
  • OfStack

This article illustrates how JSP uses custom tags to prevent repeated submission of forms. Share it for your reference. The details are as follows:

1. Write 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 = 4960707156159691747L;
  @Override
  public void doPost(HttpServletRequest requset,
      HttpServletResponse response) throws ServletException, IOException {
    //  Get the value in the input box 
    String token = requset.getParameter("tokenName");
    //  Obtain session Value in 
    String sessionToken = (String) requset.getSession().getAttribute(
        "token");
    if (token.equals(sessionToken)) {
      response.getWriter().print(" Save successfully ");
      requset.getSession().removeAttribute("token");// To ensure that session The values in do not duplicate, so remove the 
    } else {
      response.getWriter().print(" Sorry, you can't submit it repeatedly ");
    }
  }
}

2. Write classes for custom labels: 


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 method stub
    // Get uuid
    String uuid=UUID.randomUUID().toString().replace("-","");
    // Get session,pageContext  Is a domain object and also 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. Prepare the document ×. tld: 


<?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">
  <!--  Definition version  -->
  <tlib-version>1.0</tlib-version>
  <!--  Define a 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. Code in 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">
<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>

5. Interceptor to prevent garbled code: 


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(" Interception complete ");
  }
  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
  }
}

6. Configuration in 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>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>

I hope this article is helpful to everyone's JSP programming.

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