A complete servlet + Ajax Verification Code

Servlet for generating image streams

Package COM. jimo. tool; <br/> Import Java. AWT. color; <br/> Import Java. AWT. font; <br/> Import Java. AWT. graphics2d; <br/> Import Java. AWT. image. bufferedimage; <br/> Import Java. util. random; </P> <p> Import javax. imageIO. imageIO; <br/> Import javax. servlet. servletexception; <br/> Import javax. servlet. servletoutputstream; <br/> Import javax. servlet. HTTP. httpservlet; <br/> Import javax. servlet. HTTP. httpservletrequ Est; <br/> Import javax. servlet. HTTP. httpservletresponse; <br/> Import javax. servlet. HTTP. httpsession; </P> <p>/** <br/> * package name: COM. skcc. sample. action <br/> * file name: verifycodeservlet. java <br/> * Author: Administrator <br/> * Date: 2008-9-4 <br/> * description: verifycodeservlet <br/> */<br/> public class verifycodeservlet extends httpservlet {</P> <p>/** <br/> * width of the Verification Code image. <Br/> */<br/> private int width = 60; </P> <p>/** <br/> * Height of the Verification Code image. <Br/> */<br/> private int Height = 20; </P> <p>/** <br/> * number of characters in the Verification Code <br/> */<br/> private int codecount = 4; </P> <p>/** <br/> * XX <br/> */<br/> private int xx = 0; </P> <p>/** <br/> * font height <br/> */<br/> private int fontheight; </P> <p>/** <br/> * Codey <br/> */<br/> private int Codey; </P> <p>/** <br/> * codesequence <br/> */<br/> char [] codesequence = {'A', 'B ', 'C', 'D', 'E', 'F', 'G ',' H', 'I', 'J', <br/> 'k', 'l', 'M', 'n', 'O', 'P ', 'Q', 'R', 's', 't', 'U', 'V', 'w', <br/> 'x', 'y ', 'Z', '0', '1', '2', '3', '4', '5', '6', '7', '8 ', '9'}; </P> <p>/** <br/> * initialize and verify image attributes <br/> */<br/> Public void Init () throws servletexception {<br/> // from the web. get the initial information in XML <br/> // width <br/> string strwidth = This. getinitparameter ("width"); <br/> // height <br/> string strheight = This. getinitparameter ("Height"); <br/> // number of characters <br/> string strcodecount = This. getinitparameter ("codecount"); </P> <p> // convert the configuration information to a value <br/> try {<br/> If (strwidth! = NULL & strwidth. Length ()! = 0) {<br/> width = integer. parseint (strwidth); <br/>}< br/> If (strheight! = NULL & strheight. Length ()! = 0) {<br/> Height = integer. parseint (strheight); <br/>}< br/> If (strcodecount! = NULL & strcodecount. Length ()! = 0) {<br/> codecount = integer. parseint (strcodecount); <br/>}< br/>} catch (numberformatexception e) {<br/> E. printstacktrace (); <br/>}</P> <p> xx = width/(codecount + 1); <br/> fontheight = height-2; <br/> Codey = height-4; </P> <p >}</P> <p>/** <br/> * @ Param req <br/> * @ Param resP <br/> *@ throws servletexception <br/> * @ throws Java. io. ioexception <br/> */<br/> protected void Serv Ice (httpservletrequest req, httpservletresponse resp) <br/> throws servletexception, Java. io. ioexception {</P> <p> // define the image buffer <br/> bufferedimage buffimg = new bufferedimage (width, height, <br/> bufferedimage. type_int_rgb); <br/> graphics2d GD = buffimg. creategraphics (); </P> <p> // create a random number generator class <br/> random = new random (); </P> <p> // fill the image in white. <br/> GD. setcolor (color. white); <br/> GD. fillr ECT (0, 0, width, height); </P> <p> // create a font. The font size depends on the Image Height. <Br/> Font font = new font ("fixedsys", Font. Plain, fontheight); <br/> // set the font. <Br/> GD. setfont (font); </P> <p> // draw a border. <Br/> GD. setcolor (color. black); <br/> GD. drawrect (0, 0, width-1, height-1); </P> <p> // generates 160 random interference lines, make it difficult for other programs to detect the authentication code in the image. <Br/> GD. setcolor (color. black); <br/> for (INT I = 0; I <1; I ++) {<br/> int x = random. nextint (width); <br/> int y = random. nextint (height); <br/> int XL = random. nextint (12); <br/> int yl = random. nextint (12); <br/> GD. drawline (X, Y, x + XL, Y + yl); <br/>}</P> <p> // randomcode is used to save the randomly generated verification code, so that the user can verify after logging on. <Br/> stringbuffer randomcode = new stringbuffer (); <br/> int Red = 0, Green = 0, Blue = 0; </P> <p> // generate a random codecount verification code. <Br/> for (INT I = 0; I <codecount; I ++) {<br/> // obtain the Random verification code number. <Br/> string strrand = string. valueof (codesequence [random. nextint (36)]); <br/> // generates a random color component to construct the color value. In this way, the color values of each output number are different. <Br/> Red = random. nextint (255); <br/> Green = random. nextint (255); <br/> Blue = random. nextint (255); </P> <p> // draw the verification code to the image with a random color. <Br/> GD. setcolor (new color (red, green, blue); <br/> GD. drawstring (strrand, (I + 1) * XX, Codey); </P> <p> // combines the four random numbers. <Br/> randomcode. append (strrand); <br/>}< br/> // Save the four-digit verification code to the session. <Br/> httpsession session = req. getsession (); <br/> session. setattribute ("validatecode", randomcode. tostring (); </P> <p> // disable image caching. <Br/> resp. setheader ("Pragma", "No-Cache"); <br/> resp. setheader ("cache-control", "No-Cache"); <br/> resp. setdateheader ("expires", 0); </P> <p> resp. setcontenttype ("image/JPEG"); </P> <p> // output the image to the servlet output stream. <Br/> servletoutputstream SOS = resp. getoutputstream (); <br/> ImageIO. write (buffimg, "Jpeg", SOS); <br/> SOS. close (); <br/>}< br/>}

 

Servlet processing result

Package COM. jimo. tool; <br/> Import Java. io. ioexception; <br/> Import Java. io. printwriter; </P> <p> Import javax. servlet. servletexception; <br/> Import javax. servlet. HTTP. httpservlet; <br/> Import javax. servlet. HTTP. httpservletrequest; <br/> Import javax. servlet. HTTP. httpservletresponse; </P> <p>/** <br/> * package name: COM. skcc. sample. action <br/> * file name: resultservlet. java <br/> * Author: Administrator <br/> * Date: 2008-9-4 <br/> * description: resultservlet <br/> */<br/> public class resultservlet extends httpservlet {</P> <p>/** <br/> * The doget method of the servlet. <br> <br/> * this method is called when a form has its tag Value Method equals to get. <br/> * @ Param request the request send by the client to the server <br/> * @ Param response the response send by the server to the client <br/> * @ throws servletexception if an error occurred <br/> * @ throws ioexception if an error occurred <br/> */<br/> Public void doget (httpservletrequest request, httpservletresponse response) <br/> throws servletexception, ioexception {<br/> dopost (request, response ); <br/>}</P> <p>/** <br/> * The dopost method of the servlet. <br> <br/> * this method is called when a form has its tag Value Method equals to post. <br/> * @ Param request the request send by the client to the server <br/> * @ Param response the response send by the server to the client <br/> * @ throws servletexception if an error occurred <br/> * @ throws ioexception if an error occurred <br/> */<br/> Public void dopost (httpservletrequest request, httpservletresponse response) <br/> throws servletexception, ioexception {</P> <p> response. setcontenttype ("text/html; charset = UTF-8"); <br/> string validatec = request. getsession (). getattribute ("validatecode "). tostring (); <br/> string verycode = request. getparameter ("C"); <br/> printwriter out = response. getwriter (); <br/> If (verycode = NULL | "". specified signorecase (verycode) {<br/> out. println ("the verification code is blank"); <br/>}else {<br/> If (validatec. specified signorecase (verycode) {<br/> out. println ("correct Verification Code"); <br/>}else {<br/> out. println ("Incorrect verification code"); <br/>}< br/> out. flush (); <br/> out. close (); <br/>}< br/>}

 

Page call:

<Script language = "JavaScript" type = "text/JavaScript" src = "JS/checknum. js"> </SCRIPT>

 

<Input id ="Verycode"Name ="Verycode"Type ="Text"/>

<IMG id ="Imgobj"Alt =""Src ="Verifycodeservlet"Align ="Middle"/>

<Input type ="Button"Onclick = "changeimg ()" value ="Change one"/>

<Div id ="Info"Style ="Color: red; font-size: 12px; font-weight: 600"> The verification code is empty. </div>

 

Verify the JS file:

Function changeimg () {<br/> // alert ("in changeimg"); <br/> var imgsrc = document. getelementbyid ("imgobj"); <br/> // alert ("" + imgsrc); <br/> var oldsrc = imgsrc. SRC; <br/> // alert ("" + oldsrc); <br/> var newsrc = chgurl (oldsrc ); <br/> // alert ("" + newsrc); <br/> imgsrc. src = newsrc; <br/>}< br/> // timestamp <br/> // to make the image generated inconsistent each time, the browser is not allowed to read the cache, therefore, the timestamp <br/> function chgurl (URL) {<br/> // alert ("in chgurl"); <br/> VaR timestamp = (new date ()). valueof (); <br/> // alert ("" + URL); <br/> var postion = URL. indexof ("? "); <Br/> // alert (" "+ postion); <br/> If (postion> = 0) {<br/> var suburl = URL. substr (0, postion); <br/> // alert ("" + suburl); <br/> url = suburl + "? Timestamp = "+ timestamp; <br/>} else {<br/> url = URL + "? Timestamp = "+ timestamp; <br/>}< br/> return URL; <br/>}</P> <p> function isrightcode () {<br/> var code = $ ("# verycode "). ATTR ("value"); <br/> // alert (CODE); <br/> code = "C =" + code; <br/> $. ajax ({<br/> type: "Post", <br/> URL: "resultservlet", <br/> data: code, <br/> success: callback <br/>}); <br/>}</P> <p> function callback (data) {<br/>$ ("# Info" ).html (data); <br/>}