Java CAPTCHA Source Code principle

This article is divided into four steps:

First, the new servlet class named: Checkcodeservlet

Second, copy the following code into the new Checkcodeservlet class, modify your own package name

Package com.seesun2012.Servlet; //This is my package name.

Import Java.awt.Color;
Import Java.awt.Font;
Import Java.awt.Graphics;
Import Java.awt.image.BufferedImage;
Import java.io.IOException;
Import Java.io.OutputStream;
Import Java.util.Random;

Import Javax.imageio.ImageIO;
Import javax.servlet.ServletException;
Import Javax.servlet.http.HttpServlet;
Import Javax.servlet.http.HttpServletRequest;
Import Javax.servlet.http.HttpServletResponse;

public class Checkcodeservlet extends HttpServlet {
Generate the font immediately
Private Font GetFont () {
Create a random object to generate a stochastic number
Random random = new random ();
Create a font array that is used to install font objects of different fonts
Font font[] = new FONT[5];
Font[0] = new Font ("Ravie", Font.plain, 24);
FONT[1] = new Font ("Antique Olive Compact", Font.plain, 24);
FONT[2] = new Font ("Forte", Font.plain, 24);
FONT[3] = new Font ("Wide Latin", Font.plain, 24);
FONT[4] = new Font ("Gill Sans Ultra Bold", Font.plain, 24);
Return Font[random.nextint (5)];
}

protected void Doget (HttpServletRequest req, HttpServletResponse resp)
Throws Servletexception, IOException {
Setting the response header Content-type type
Resp.setcontenttype ("Image/jpeg");
OutputStream OS = Resp.getoutputstream ();
int width =, height = 30;
Establishing a specified width, height, and BufferedImage object
BufferedImage image = new BufferedImage (width, height,bufferedimage.type_int_rgb);

Graphics g = image.getgraphics (); The brush is drawn on the image
Color C = G.getcolor (); Save the color of the current brush
Fill Rectangle
G.fillrect (0, 0, width, height);


char[] ch = "abcdefghjkmnpqrstuvwxyz2345678901". ToCharArray (); The resulting string does not include I l (lowercase l) o (lowercase o) 1 (number 1) 0 (number 0)
int length = Ch.length; The length of the string immediately
String SRand = ""; Save the resulting string
Random random = new random ();
for (int i = 0; i < 4; i++) {
Set font
G.setfont (GetFont ());
A 0-9 number is generated
String rand = new Character (ch[random.nextint (length)]). ToString ();
SRand + = rand;
Set Random Colors
G.setcolor (New Color (Random.nextint (255), Random.nextint (255), Random.nextint (255)));
g.DrawString (Rand, i + 6, 25);
}
Generate a random point of interference
for (int i = 0; i <; i++) {
int x1 = random.nextint (width);
int y1 = random.nextint (height);
G.drawoval (x1, y1, 2, 2);
}
Set the color of the brush back again
G.setcolor (c);
Releases the context of this graphic and all system resources it uses.
G.dispose ();

Record verification code to session
Req.getsession (). SetAttribute ("Safecode", SRand);
Output image to Page
Imageio.write (Image, "JPEG", OS);

}

protected void DoPost (HttpServletRequest req, HttpServletResponse resp)
Throws Servletexception, IOException {
Doget (req, resp);
}

}

Third, add the following JavaScript code to the JSP page in the page (if you must refer to the Jquery-1.11.0.min.js script):

<script type= "Text/javascript" >
function changeimg () {
var imgobj = document.getElementById ("img");
IMGOBJ.SRC = "checkcodeservlet?ran=" + math.random ();
}
</script>

Iv. add in the body tag, post is the method of submission:

<form action= "to be processed and verify the servlet name" id= "Commentform" method= "POST" >

<span class= "Login_txt" > Verification Code:</span>

<input class= "" Name= "code" type= "Rext" value= "" Maxlength=4 size=10/>

<a href= "javascript:changeimg ()" class= "login-text03" > can't see Clearly, change picture </a>

</form>

Java CAPTCHA Source Code principle