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Java Verification Code Detailed

Source: Internet
Author: User
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1 using the servlet to implement the verification code, the knowledge points involved in Java drawing technology and session to save data.

HTML page

1 <HTML>2 <Imagesrc= ' images/logo1.jpg '/><HR/>3 <Head><BR/><title>Login</title> <BR/><H1>Welcome to Login</H1></Head>4 <Body>5 <formAction= '/loginvalid/loginverify 'Method= ' Post '>6User id:<inputtype= ' text 'name= ' UserID 'value= ' '>7User password:<inputtype= ' Password 'name= ' Password 'value= ' '>9Verification Code:<inputtype= ' text 'name= ' Inputcode '/>  <imgID= ' Imgobj 'src= '/loginvalid/createcode2 '/><ahref= ' javascript:changeimg () '>Another one.</a>Ten <inputtype= ' Submit 'value= ' Login '/> One </form> A </Body>
 - <Scripttype= ' Text/javascript '> - functionchangeimg () {
var Time= NewDate ();
document.getElementById ('imgobj'). SRC='/loginvalid/createcode2?d='+Time ;
} the </Script> - </HTML>

　　

Tool class for generating verification code

1  Public classCodeutil {2     3     //Picture Width4     Private Static Final intimg_w=120;5     //Picture Height6     Private Static Final intImg_h=30;7     //number of verification code characters8     Private Static Final intNum_chs=5;9     //Verification code contains the specific charactersTen     Private Static Char[] CHS = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890". ToCharArray (); One     Private StaticRandom Rand =NewRandom (); A      -     //image X-axis, y-axis position cardinality -     Private Static intCodeX = 20; the     Private Static intCodey = 25; -      -     //Font Size -     Private Static intFonth = 25; +      -      Public StaticMap<string, object>generateimage () +     { ABufferedImage image =Newbufferedimage (img_w, Img_h, Bufferedimage.type_int_rgb); atGraphics g =image.getgraphics (); -          -         //Set picture background color to white - G.setcolor (color.white); -G.fillrect (0, 0, img_w, img_h); -          in         //Set Font size -Font font =NewFont ("Fixedsys", Font.Bold, fonth); to G.setfont (font); +          -         //Draw Border the G.setcolor (color.black); *G.drawrect (0, 0, img_w, img_h); $         Panax Notoginseng G.setcolor (color.black); -         //randomly generates 30 lines of interference the          for(inti=0; i<30; i++) +         { A             intx =Rand.nextint (img_w); the             inty =Rand.nextint (img_h); +             intXL = Rand.nextint (20); -             intYL = Rand.nextint (20); $              $ g.drawline (x, Y, XL, yl);  -         } -          theStringBuilder SB =NewStringBuilder (); -          for(inti=0; i<num_chs; i++)Wuyi         { the             //randomly get a character from a string -String Code =string.valueof (Chs[rand.nextint (chs.length)); Wu             //randomly set brush color -G.setcolor (NewColor (Rand.nextint (255), Rand.nextint (255), Rand.nextint (255))); Aboutg.DrawString (Code, (i+1) *CodeX, Codey); $ sb.append (code); -         } -          -map<string, object> map =NewHashmap<string, object>(); AMap.put ("Code", sb.tostring ()); +Map.put ("Codeimage", image); the         returnmap; -          $     } the  the}

Servlet that generates a verification code in the background

1         //prevent browser from caching random pictures2Response.setdateheader ("Expires", 1);3Response.setheader ("Cache-control", "No-cache");4Response.setheader ("Pragma", "No-cache");5         6         //notifies the client to open a picture to send past data7Response.setheader ("Content-type", "Image/jpeg");8         9map<string, object> map =codeutil.generateimage ();Ten         //Save the verification code to session OneRequest.getsession (). SetAttribute ("Checkcode", Map.get ("code")); AImageio.write ((renderedimage) map.get ("Codeimage"), "JPG", Response.getoutputstream ());

Background verifies that the user entered a validation code that is consistent with the displayed servlet class

2HttpSession session =request.getsession ();3String secode = (string) session.getattribute ("Checkcode");4String inputcode = (string) request.getparameter ("Inputcode");5         if(Secode.equals (inputcode))6         {7Request.getrequestdispatcher ("/main"). Forward (request, response);8         }9         ElseTen         { OneRequest.getrequestdispatcher ("/err"). Forward (request, response); A}

　　

Java Verification Code Detailed

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