Generate 4 random numbers and clutter background pictures, the number and background color will change, server-side refresh (with History.go (-1) will also change)
File image.jsp that produces the captcha picture
| <%@ page contenttype= "image/jpeg" import= "java.awt.*, Java.awt.image.*,java.util.*,javax.imageio.* "%> <%! Color getrandcolor (int fc,int BC) {//random color for a given range Random Random = new Random (); if (fc>255) fc=255; if (bc>255) bc=255; int R=fc+random.nextint (BC-FC); int G=fc+random.nextint (BC-FC); int B=fc+random.nextint (BC-FC); return new Color (R,G,B); } %> <% Set Page Not Cached Response.setheader ("Pragma", "No-cache"); Response.setheader ("Cache-control", "No-cache"); Response.setdateheader ("Expires", 0); Create an image in memory int width=60, height=20; BufferedImage image = new BufferedImage (width, height, bufferedimage.type_int_rgb); Get Graphics context Graphics g = image.getgraphics (); Generate Random Class Random Random = new Random (); Set Background color G.setcolor (Getrandcolor (200,250)); G.fillrect (0, 0, width, height); Set font G.setfont (New Font ("Times New Roman", font.plain,18)); Draw a border G.setcolor (New Color ()); G.drawrect (0,0,width-1,height-1); Randomly generated 155 lines of interference, so that the image of the authentication code is not easily detected by other programs G.setcolor (Getrandcolor (160,200)); for (int i=0;i<155;i++) { int x = random.nextint (width); int y = random.nextint (height); int xl = Random.nextint (12); int yl = Random.nextint (12); G.drawline (X,y,x+xl,y+yl); } Take a randomly generated authentication code (4 digits) String srand= ""; for (int i=0;i<4;i++) { String rand=string.valueof (Random.nextint (10)); Srand+=rand; Display the authentication code in the image G.setcolor (New Color (20+random.nextint), 20+random.nextint (a), 20+random.nextint (110)); The call function comes out with the same color, possibly because the seed is too close, so it can only be generated directly g.DrawString (rand,13*i+6,16); } Save authentication Code in session Session.setattribute ("Rand", SRand); Image entry into force G.dispose (); Output image to Page Imageio.write (Image, "JPEG", Response.getoutputstream ()); %> |
| <%@ page contenttype= "text/html;charset=gb2312"%> <! DOCTYPE HTML PUBLIC "-//w3c//dtd HTML 4.01 transitional//en" > <title> Authentication Code Input page </title> <meta http-equiv= "Content-type" content= "text/html; charset=gb2312 "> <meta http-equiv= "Pragma" content= "No-cache" > <meta http-equiv= "Cache-control" content= "No-cache" > <meta http-equiv= "Expires" content= "0" > <body> <form method=post action= "check.jsp" > <table> <tr> <TD align=left> System-generated authentication code:</td> <td></td> </tr> <tr> <TD align=left> Enter the authentication code above:</td> <td><input type=text name=rand maxlength=4 value= "" ></td> </tr> <tr> <TD colspan=2 align=center><input type=submit value= "Submit Detection" ></td> </tr> </form> </body> |
| <%@ page contenttype= "text/html; charset=gb2312 "language=" java "import=" java.sql.* "errorpage=" "%>" <title> Authentication Code Verification page </title> <meta http-equiv= "Content-type" content= "text/html; charset=gb2312 "> <meta http-equiv= "Pragma" content= "No-cache" > <meta http-equiv= "Cache-control" content= "No-cache" > <meta http-equiv= "Expires" content= "0" > <body> <% String rand = (string) session.getattribute ("Rand"); String input = Request.getparameter ("Rand"); %> The authentication code generated by the system is: <%= Rand%><br> The authentication code you have entered is: <%= input%><br> <br> <% if (rand.equals (input)) { %> <font color=green> Input the same, authentication success! </font> <% } else { %> <font color=red> input is different, authentication failed! </font> <% } %> </body> |
Start building with 50+ products and up to 12 months usage for Elastic Compute Service
1 on 1 presale consultation
24/7 Technical Support 6 Free Tickets per Quarter Faster Response
Alibaba Cloud offers highly flexible support services tailored to meet your exact needs.
A comprehensive suite of global cloud computing services to power your business
Payment Methods We Support
