Summary of JSP website development: 13th and website development: 13th

Summary of JSP website development: 13th and website development: 13th

After adding the filter class to the previous article, this article briefly introduces how to implement the verification code. What is the role of the verification code? 1. prevent malicious registration. 2. prevent malicious submission. 3. Prevent account theft. In general, the verification code is used to prevent unauthorized operations, however, it should be noted that the verification code is a function that affects the user experience. Therefore, some websites will prompt users to enter the verification code only after the user fails to perform the first operation by setting parameters, this can be said to be an improvement in the verification code. It is useless. Let's start to implement our verification code.

1. Implementation:

　　

2. index. jsp:

Some JavaScript operations are added during the interface design. If you have any questions, leave a message.

<% @ Page language = "java" import = "java. util. * "pageEncoding =" UTF-8 "%> <% String path = request. getContextPath (); String basePath = request. getScheme () + ": //" + request. getServerName () + ":" + request. getServerPort () + path + "/"; %> <! Doctype html public "-// W3C // dtd html 4.01 Transitional // EN"> 
3. Generate the verification code select:
public void doPost(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        BufferedImage bi = new BufferedImage(68, 22, BufferedImage.TYPE_INT_RGB);        Graphics g = bi.getGraphics();        Color color = new Color(200, 130, 255);        g.setColor(color);        g.fillRect(0, 0, 68, 22);                char [] ch = "QWERTYUIOPASDFGHJKLZXCVBNM1234567890zxcvbnmlkjhgfdsaqwertyuiop".toCharArray();        Random r = new Random();        StringBuffer buf = new StringBuffer();        int len = 0;        for(int i=0; i<4; i++){            len = r.nextInt(ch.length);            g.setColor(new Color(r.nextInt(150), r.nextInt(255), r.nextInt(200)));            g.drawString(ch[len]+"", (i*15)+3, 18);            buf.append(ch[len]);        }        String code = buf.toString();        request.getSession().setAttribute("code", code);        ImageIO.write(bi, "JPG", response.getOutputStream());    }
4. Verify selelct:
Public void doPost (HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {request. setCharacterEncoding ("UTF-8"); response. setCharacterEncoding ("UTF-8"); response. setContentType ("text/html"); PrintWriter out = response. getWriter (); String code = request. getParameter ("code"); String imgCode = (String) request. getSession (). getAttribute ("code"); if (imgCode. equalsIgnoreCase (code) {out. println ("Logon successful");} else {out. println ("Logon Failed ");}}
Here, we have achieved the verification code effect. For the verification code that generates the Chinese character verification code and the mathematical expression, we will study it on our own. The ideas have been introduced to you, and the summary of JSP is as follows, at present, it is almost impossible to upload and download files. It is estimated that we will share it with you in the following days. Of course, if you can implement it, I hope you can give more advice.