Captcha validation using JavaScript in JSP -


i have captcha validation code , set captcha string session , in validating script function null.

i'm using javascript inside jsp page.

<script> function validatecaptcha(){ var v='<%=session.getattribute("captcha")%>' alert (v); } </script>       <form method="post" onsubmit="validatecaptcha()">      <input type="text" name="code">      <img src="<c:url value="captcha.jsp"></c:url>">       <input type="submit" value="submit">     </form>      </body>     </html>

i have captcha.jsp generate captcha cannot session value in javascript.

 <%int width = 150;     int height = 50;      char data[][] = {         { '4', 'e', 'g', 'v', 'o', 'f', 'x' },         { 'd', 't', 't', '5', 'o', '7', 'x' },         { '5', 'e', '7', 'c', '6', 'p', 't' },         { 'l', 'j', '5', 't', 'x','6' ,'g'},         { '9', 'f', '5', 't', 'x','e' ,'7'},         { 'f', '5', 't', 'b', 'b', 's', 'd' },         { 'u', 'b', 'u', 'n', 't', 'u' },         { 'j', 'e', 'e','a','y','1','2','5','6', }     };       bufferedimage bufferedimage = new bufferedimage(width, height,                    bufferedimage.type_int_rgb);      graphics2d g2d = bufferedimage.creategraphics();      font font = new font("arial", font.bold, 18);     g2d.setfont(font);     renderinghints rh = new renderinghints(            renderinghints.key_antialiasing,            renderinghints.value_antialias_on);     rh.put(renderinghints.key_rendering,             renderinghints.value_render_quality);     g2d.setrenderinghints(rh);     gradientpaint gp = new gradientpaint(0, 0,      color.red, 0, height/2, color.black, true);     g2d.setpaint(gp);     g2d.fillrect(0, 0, width, height);     g2d.setcolor(new color(255, 153, 0));     random r = new random();     int index = math.abs(r.nextint()) % 5;     string captcha = string.copyvalueof(data[index]);     request.getsession().setattribute("captcha", captcha );     int x = 0;      int y = 0;     (int i=0; i<data[index].length; i++) {         x += 10 + (math.abs(r.nextint()) % 15);         y = 20 + math.abs(r.nextint()) % 20;         g2d.drawchars(data[index], i, 1, x, y);     }     g2d.dispose();     response.setcontenttype("image/png");     outputstream os = response.getoutputstream();     imageio.write(bufferedimage, "png", os);     os.close();      %>


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