hi,
you can use the recaptcha library for java is pretty simple to use:
On client:
final RecaptchaWidget rw = new RecaptchaWidget(RECAPTCHAKEY);
panel.add(new HTML("<div id=\"recaptcha_image\"></div>"));
TextBox response = new TextBox();
response.getElement().setId("recaptcha_response_field");
panel.add(response);
you can make a reload button by implementing the onClick and calling
rw.reload(); it will refresh the image and clear the response field
when you call the server you must send the rw.getChallenge() and
rw.getResponse()
then on server side:
.. String challenge,String response)
ReCaptcha r = ReCaptchaFactory.newReCaptcha(KEY,SECRET, true);
if (!r.checkAnswer(getThreadLocalRequest().getRemoteAddr().toString(),
challenge,response).isValid()) throw new Exception("Invalid captcha
response");
It was the simplest way i found hope it helps.
On 14 Abr, 21:55, Carlo <[email protected]> wrote:
> Hi Ankit,
>
> Maybe, I can help you.
>
> I write below the code than I use to do Captcha check.
>
> In the form panel:
>
> #########
> FormPanel form = new FormPanel();
> ....
> VerticalPanel vp = new VerticalPanel();
>
> HorizontalPanel hp = new HorizontalPanel();
> hp.setSpacing(10);
>
> codeCheck = new TextField<String>();
> codeCheck.setFieldLabel("Controllo");
> codeCheck.setAllowBlank(false);
>
> verifyImage = new Image("verify.png");
> hp.add(verifyImage);
> hp.setCellHorizontalAlignment(verifyImage,
> HasAlignment.ALIGN_RIGHT);
> hp.setCellWidth(verifyImage, "170px");
>
> final Button clickImage = new Button("New image");
> clickImage.addSelectionListener(new
> SelectionListener<ButtonEvent>()
> {
> @Override
> public void componentSelected(ButtonEvent ce) {
> codeCheck.setValue("");
> int rand = Random.nextInt();
> String url = "verify.png?rand=" + rand;
> verifyImage.setUrl(url);
> }
> });
> hp.add(clickImage);
>
> vp.add(hp);
>
> HTML info = new HTML("Write in the check field the sequence of
> characters in the image.");
> info.setStyleName("x-label");
> vp.add(info);
>
> panel.add(vp);
>
> panel.add(codeCheck);
>
> errorCaptcha = new HTML("");
> errorCaptcha.setStyleName("x-label");
> errorCaptcha.addStyleName("x-label-red");
> vp.add(errorCaptcha);
>
> Button btn = new Button("Check");
> btn.addSelectionListener(new SelectionListener<ButtonEvent>()
> {
> @Override
> public void componentSelected(ButtonEvent ce) {
> if (!panel.isValid() ||
> codeCheck.getValue()==null) {
> return;
> }
> service.checkCode(codeCheck.getValue(), new
> AsyncCallback<String>() {
> public void onFailure(Throwable
> caught) {
>
> MessageBox.alert("error",caught.getMessage(),null);
> }
> public void onSuccess(String result) {
> if
> (((String)result).equals("Sorry please enter correct code for
> verification.")){
>
> errorCaptcha.setHTML(result);
> return;
> } else {
>
> errorCaptcha.setHTML("");
> }
> }
> });
> // panel.submit(); // this is your form
> submit
> }
> });
> panel.addButton(btn);
>
> ##############
> Now, the GWT RPC servlet code (it's very simple):
> ##############
>
> public String checkCode(String entercode)
> {
> session = getThreadLocalRequest().getSession();
> String code =
> (String)session.getAttribute("verification.code");
> String attempt = entercode;
> String msg = "";
>
> if (code!=null && code.equals(attempt)){
> msg = "Correct verification code";
> } else {
> msg = "Sorry please enter correct code for
> verification.";
> }
> return msg;
> }
>
> ##############
> In the reality the url "verify.png" for the image is a servlet, and
> you must define this into web.xml:
> ##############
>
> <servlet>
> <servlet-name>VerificationServlet</servlet-name>
>
> <servlet-class>com.yourpackage.server.VerificationServlet</servlet-
> class>
> </servlet>
>
> <servlet-mapping>
> <servlet-name>VerificationServlet</servlet-name>
> <url-pattern>/verify.png</url-pattern>
> </servlet-mapping>
>
> ##############
> Now the code about VerificationServlet:
> ##############
> package com.yourpackage.server;
>
> import java.io.*;
> import javax.servlet.ServletContext;
> import javax.servlet.*;
> import javax.servlet.http.HttpServlet;
> import javax.servlet.http.HttpServletRequest;
> import javax.servlet.http.HttpServletResponse;
> import javax.servlet.http.HttpSession;
>
> public class VerificationServlet extends HttpServlet
> {
> private static final long serialVersionUID = 1L;
> HttpSession session;
>
> ServletContext context = null;
>
> public void init(ServletConfig config) throws ServletException
> {
> super.init(config);
> context = config.getServletContext();
> }
>
> @Override
> protected void doGet(HttpServletRequest request,
> HttpServletResponse response) throws ServletException, IOException
> {
> session = request.getSession(true);
> response.setHeader("Pragma", "public");
> response.setHeader("cache-control", "max-age=0,no-cache, no-
> store,must-revalidate, proxy-revalidate, s-maxage=0");
> response.setDateHeader("Expires", 0);
> response.setContentType("image/png");
>
> ImageVerification verification = new
> ImageVerification(response.getOutputStream());
> String code = verification.getVerificationValue();
> session.setAttribute("verification.code", code);
>
> response.flushBuffer();
> }
>
> }
>
> ##############
> And the last is the code about ImageVerification:
> ##############
> package com.yourpackage.server;
>
> import java.awt.Color;
> import java.awt.Font;
> import java.awt.Graphics2D;
> import java.awt.geom.AffineTransform;
> import java.awt.image.BufferedImage;
> import java.io.IOException;
> import java.io.OutputStream;
> import java.util.Random;
> import java.util.UUID;
>
> import javax.imageio.ImageIO;
>
> /**
> * ImageVerification is a simple utility class for
> * creating an image verification PNG file that will
> * allow you to make sure that only a human can read
> * the alphanumeric values and enter them into a text
> * field during verification. <P>
> *
> */
> public class ImageVerification
> {
> private String value;
>
> public ImageVerification (OutputStream out) throws IOException
> {
> this(50,120,out);
> }
> public ImageVerification (int height, int width, OutputStream out)
> throws IOException
> {
> BufferedImage bimage = new BufferedImage(width, height,
> BufferedImage.TYPE_INT_RGB);
> Random rand=new Random(System.currentTimeMillis());
> Graphics2D g = bimage.createGraphics();
>
> // create a random color
> Color color = new Color(rand.nextInt(255), rand.nextInt(255),
> rand.nextInt(255));
>
> // the the background to the random color to fill the
> // background and make it darker
> g.setColor(color.darker());
> g.fillRect(0, 0, width, height);
>
> // set the font
> g.setFont(new Font("arial",Font.BOLD,36));
>
> // generate a random value
> this.value =
> UUID.randomUUID().toString().replace("-","").substring(0,5);
>
> int w = (g.getFontMetrics()).stringWidth(value);
> int d = (g.getFontMetrics()).getDescent();
> int a = (g.getFontMetrics()).getMaxAscent();
>
> int x = 0, y =0;
>
> // randomly set the color and draw some straight lines through
> it
> for (int i = 0; i < height; i += 5)
> {
> g.setColor(new Color(rand.nextInt(255), rand.nextInt(255),
> rand.nextInt(255)));
> g.drawLine(x, y + i, width, y+i);
> }
>
> // reset x and y
> x=0;
> y=0;
>
> // randomly set the color of the lines and just draw think at
> an angle
> for (int i = 0; i < height; i += 5)
> {
> g.setColor(new Color(rand.nextInt(255), rand.nextInt(255),
> rand.nextInt(255)));
> g.drawLine(x, y + d - i, width + w, height + d - i);
> }
>
> // randomly set the color and make it really bright for more
> readability
> g.setColor(new Color(rand.nextInt(255), rand.nextInt(255),
> rand.nextInt(255)).brighter().brighter());
>
> // we need to position the text in the center of the box
> x = width/2 - w/2;
> y = height/2 + a/2 - 2;
>
> // affine transform is used to rock the text a bit
> AffineTransform fontAT = new AffineTransform();
> int xp = x-2;
> // walk through each character and rotate it randomly
> for (int c=0;c<value.length();c++)
> {
> // apply a random radian either left or right (left is
> half since it's too far back)
> int rotate = rand.nextInt(20);
> fontAT.rotate(rand.nextBoolean() ?
> Math.toRadians(rotate) : -Math.toRadians(rotate/2));
> Font fx = new Font("arial", Font.BOLD,
> 36).deriveFont(fontAT);
> g.setFont(fx);
> String ch = String.valueOf(value.charAt(c));
> int ht = rand.nextInt(3);
> // draw the string and move the y either up or down
> slightly
> g.drawString(ch, xp, y + (rand.nextBoolean()?-ht:ht));
> // move our pointer
> xp+=g.getFontMetrics().stringWidth(ch) + 2;
> }
>
> // write out the PNG file
> ImageIO.write(bimage, "png", out);
> //System.out.println("DONE WRITYING NEW IMAGHE");
>
> // make sure your clean up the graphics object
> g.dispose();
> }
> /**
> * return the value to check for when the user enters it in. Make
> sure you
> * store this off in the session or something like a database and
> NOT in the
> * form of the webpage since the whole point of this exercise is
> to ensure that
> * only humans and not machines are entering the data.
> *
> * @return
> */
> public String getVerificationValue ()
> {
> return this.value;
> }
>
> }
>
> ################
> Ok, this is all.
>
> I hope this could help you.
>
> Hi
> Carlo
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