Java Generate verification Code _ go

In order to prevent malicious users, or use the software to submit some content, you have to use a verification code to block, although this will affect the user experience, but in order to avoid some problems many sites have used a verification code; this afternoon reference to the document to get a verification code, here to share; This is a Web project, first of all, a page, Here is just a display verification code page index.jsp, using the default generated on it, the form did not commit, as follows

<%@ page language= "java" import= "java.util.*" pageencoding= "UTF-8"%><! DOCTYPE HTML PUBLIC "-//w3c//dtd HTML 4.01 transitional//en" >
 Below is the background code, here is a servlet, do not forget to configure the request URL in Web. xml 
 
Import java.io.IOException; Import Javax.servlet.servletexception;import Javax.servlet.http.httpservlet;import Javax.servlet.http.httpservletrequest;import Javax.servlet.http.HttpServletResponse;     public class Imageservlet extends HttpServlet {private static final long serialversionuid = 1L; public void doget (HttpServletRequest request, httpservletresponse response) throws Servletexception, Ioexceptio n {response.setcontenttype ("image/jpeg");//Set the appropriate type, telling the browser output is the picture Response.setheader ("Pragma", "No-cache");        /Set the response header information to tell the browser not to cache this content Response.setheader ("Cache-control", "No-cache");        Response.setdateheader ("Expire", 0);        Randomvalidatecode Randomvalidatecode = new Randomvalidatecode (); try {randomvalidatecode.getrandcode (request, response);//Output Picture method} catch (Exception e) {E.PR        Intstacktrace (); }} public void DoPost (HttpServletRequest request, httpservletresponse response) throws SErvletexception, IOException {doget (request, response); } }
 How the class generates a verification code 
 
Import Java.awt.color;import java.awt.font;import Java.awt.graphics;import Java.awt.image.bufferedimage;import Java.util.Random; Import Javax.imageio.imageio;import Javax.servlet.http.httpservletrequest;import Javax.servlet.http.httpservletresponse;import javax.servlet.http.HttpSession;    public class Randomvalidatecode {public static final String Randomcodekey = "Randomvalidatecodekey";//Key placed in session    Private random random = new random (); private string randstring = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";//randomly generated string private int width = 80;//picture width private     int height = 26;//picture high private int linesize = 40;//number of interference lines private int stringnum = 4;//randomly generated characters/* * Get fonts */    Private Font GetFont () {return new font ("Fixedsys", font.center_baseline,18);        }/* * Get color */Private color getrandcolor (int fc,int BC) {if (FC > 255) FC = 255;        if (BC > 255) BC = 255;      int r = FC + Random.nextint (bc-fc-16);  int g = FC + Random.nextint (BC-FC-14);        int B = FC + Random.nextint (bc-fc-18);    return new Color (R,G,B); /** * Generate random pictures */public void Getrandcode (HttpServletRequest request, HttpServletResponse respons        e) {HttpSession session = Request.getsession (); The BufferedImage class is an image class with buffers, and the image class is the class that describes the image information BufferedImage image = new BufferedImage (width,height,bufferedimage.        TYPE_INT_BGR);        Graphics g = image.getgraphics ();//The Graphics object that produces the image object, the object can be g.fillrect (0, 0, width, height) for various drawing operations on the image;        G.setfont (New Font ("Times New Roman", font.roman_baseline,18));        G.setcolor (Getrandcolor (110, 133));        Draw the interference line for (int i=0;i<=linesize;i++) {drowline (g);        }//Draw random character String randomstring = "";        for (int i=1;i<=stringnum;i++) {randomstring=drowstring (g,randomstring,i);        } session.removeattribute (Randomcodekey); Session.setattribute (RANDOMCodekey, RandomString);        System.out.println (RandomString);        G.dispose (); try {imageio.write (image, "JPEG", Response.getoutputstream ());//Output The in-memory picture to the client} catch (Exception        e) {e.printstacktrace (); }}/* * Draw String */private string drowstring (Graphics g,string randomstring,int i) {G.setfont (GETFO        NT ());        G.setcolor (New Color (Random.nextint (101), Random.nextint (111), Random.nextint (121)));        String rand = string.valueof (getrandomstring (Random.nextint (Randstring.length ())));        RandomString +=rand;        G.translate (Random.nextint (3), Random.nextint (3));        g.DrawString (Rand, 13*i, 16);    return randomstring;        }/* * Draw the interference line */private void Drowline (Graphics g) {int x = random.nextint (width);        int y = random.nextint (height);        int xl = Random.nextint (13);        int yl = Random.nextint (15);    G.drawline (x, Y, X+XL, y+yl);  }/* * get random characters   */Public String getrandomstring (int num) {return string.valueof (Randstring.charat (num)); }}
 Java generic class generation CAPTCHA generated picture saved to local 
 
Import Java.awt.color;import java.awt.font;import Java.awt.graphics2d;import Java.awt.image.bufferedimage;import Java.io.file;import Java.util.random;import Javax.imageio.ImageIO;    The width of the public class Validatecode {/** * * * *//Captcha picture.    private int width = 350;    The height of the captcha picture.    private int height = 100;     Number of captcha characters private int codecount = 4;    private int x = 0;    Font height private int fontheight;     private int Codey; Char[] codesequence = {' A ', ' B ', ' C ', ' D ', ' E ', ' F ', ' G ', ' H ', ' I ', ' J ', ' K ', ' L ', ' M ', ' N ', ' P ', ' Q ', ' R ', ' S     ', ' T ', ' U ', ' V ', ' W ', ' X ', ' Y ', ' Z ', ' 1 ', ' 2 ', ' 3 ', ' 4 ', ' 5 ', ' 6 ', ' 7 ', ' 8 ', ' 9 '};        /** * Initialize Verify picture properties */public void init () {//width String strwidth = "350";        Height String strheight = "100";         Number of characters String Strcodecount = "4"; Converts the configured information into a numeric try {if (strwidth! = null && strwidth.length ()! = 0) {width = in Teger.parSeint (Strwidth); } if (strheight! = null && strheight.length ()! = 0) {height = Integer.parseint (strheigh            T); } if (Strcodecount! = null && strcodecount.length ()! = 0) {Codecount = Integer.parseint            (Strcodecount);        }} catch (NumberFormatException e) {} x = width/(codecount + 1);        Fontheight = height-2;     Codey = height-4; } protected void Service () {try {//define image buffer BufferedImage buffimg = new Bufferedimag            E (width, height, bufferedimage.type_int_rgb);             Graphics2D g = buffimg.creategraphics ();             Create a random number generator class random random = new random ();            Fills the image with a white g.setcolor (color.white);             G.fillrect (0, 0, width, height);            To create a font, the size of the font should depend on the height of the image.            Font font = new Font ("Fixedsys", Font.plain, Fontheight); //Sets the font.             G.setfont (font);            Draw a border.            G.setcolor (Color.Black);             G.drawrect (0, 0, width-1, height-1);            Randomly generates 160 lines of interference so that the authentication code in the image is not easily detected by other programs.            G.setcolor (Color.Black);                for (int i = 0; i < i++) {int x = random.nextint (width);                int y = random.nextint (height);                int xl = Random.nextint (22);                int yl = Random.nextint (22);            G.drawline (x, y, X + xl, y + yl);            }//Randomcode is used to save randomly generated verification codes so that the user can log in and verify.            StringBuffer Randomcode = new StringBuffer ();             int red = 0, green = 0, blue = 0;            Random generation of Codecount number verification code.                for (int i = 0; i < Codecount; i++) {//Get a randomly generated captcha number.                String Strrand = String. ValueOf (Codesequence[random.nextint (34)]);                Generates a random color component to construct a color value so that the output will have a different color value for each digit.             Red = random.nextint (255);   Green = Random.nextint (255);                 Blue = Random.nextint (255);                Draws the verification code into the image with a randomly generated color.                G.setcolor (New Color (red, green, blue));                 g.DrawString (Strrand, (i + 1) * x, Codey);                The resulting four random numbers are grouped together.                Randomcode.append (Strrand);            System.out.println (Strrand);             }//Save the four digit verification code to the session.             Imageio.write (buffimg, "JPEG", New File ("D://aa.jpeg"));        Output the image to the servlet output stream.        } catch (Exception e) {e.printstacktrace ();        }} public static void Main (string[] args) {Validatecode s = new Validatecode ();        S.init ();    S.service (); }}
　　
Java Generate verification Code _ go