Javaweb Learning Summary (ix)-Generate a CAPTCHA image from a servlet

Javaweb Learning Summary (ix)-Generate a CAPTCHA image from a servlet BufferedImageClass Introduction

Generate the CAPTCHA image is mainly used in a BufferedImage class, as follows:

Create a drawimage Servlet to generate the captcha picture

  1 package gacl.response.study;  2 Import Java.awt.Color;  3 Import Java.awt.Font;  4 Import Java.awt.Graphics;  5 Import Java.awt.Graphics2D;  6 Import Java.awt.image.BufferedImage;  7 Import java.io.IOException;  8 Import Java.util.Random; 9 Import Javax.imageio.ImageIO; Ten import javax.servlet.ServletException; Import Javax.servlet.http.HttpServlet; Import Javax.servlet.http.HttpServletRequest; Import Javax.servlet.http.HttpServletResponse; 14/** 15 * Generate a random image, used as a verification code.//public class DrawImage extends HttpServlet {private static final long serial Versionuid = 3038623696184546092L;      public static final int width = 120;//the width of the resulting picture is public static final int height = 30;//the height of the resulting picture 22 23 public void doget (HttpServletRequest request, httpservletresponse response) throws Servletexception, I  oexception {this.dopost (Request, response), and the public void DoPost (HttpServletRequest request, HttpservletresponSE response) throws Servletexception, IOException {String Createtypeflag = Request.getparameter ("Createtypeflag");//Receive client-passed Createtypeflag identity 31//1. Create a picture in memory. BufferedImage bi = new BufferedImage (WI DTH, Height,bufferedimage.type_int_rgb); 33//2. Get the picture of the graphics G = bi.getgraphics (); 35//3. Set the background color of the picture setbackground (g); 37//4. Set the border of the picture SetBorder (g); 39//5. Draw the interference line on the picture Drawrandomline (g); 41//6. Write a random number on the image//string random = Drawrandomnum ((graphics2d) G, "ch");//Generate Chinese captcha picture//string RA Ndom = Drawrandomnum ((graphics2d) G, "NL");//Generate a digital and alphabetic combination of CAPTCHA images//string random = Drawrandomnum ((graphics2d) G, "n") ;//Generate a pure digital code picture of//string random = Drawrandomnum ((graphics2d) G, "L");//Generate a pure letter captcha picture of String random = DRA Wrandomnum ((graphics2d) g,createtypeflag);//Generate a CAPTCHA image based on the Createtypeflag identity passed by the client 47//7. The random number exists in the session in the Reque St.getsessIon (). SetAttribute ("Checkcode", random);  49//8. Set the response header to notify the browser to open a picture as a response.setcontenttype ("image/jpeg");//equivalent to Response.setheader ("Content-type", "Image/jpeg"); 51//9. Setting the response header control browser do not cache the Response.setdateheader ("Expries",-1); Response.setheader ("Cache-control", "No-cache"); Response.setheader ("Pragma", "No-cache"); 55//10. Write the picture to the browser, Imageio.write (bi, "JPG", Response.getoutputstream ()); 57} 58 59/** 60 * Set the background color of the picture * @param g */SetBackground (Graphics g) {6 4//Set color G.setcolor (Color.White); 66//Fill area g.fillrect (0, 0, WIDTH, HEIGHT);         68} 69 70/** 71 * Set the border of the picture * @param g * * * * SetBorder private void (Graphics g) {75 Set Border color G.setcolor (color.blue); 77//Border area g.drawrect (1, 1, WIDTH-2, HEIGHT-2); 79} 80 81/** 82 * Draw random lines on the picture * @pAram G/Drawrandomline private void (Graphics g) {86//Set color G.setcolor (Color.green); 88//Set the number of lines and draw lines for (int i = 0; i < 5; i++) {$ int x1 = new Random (). Nextint (WIDTH); 9 1 int y1 = new Random (). Nextint (HEIGHT); x2 int = new Random (). Nextint (WIDTH); y2 int = new Random (). Nextint (HEIGHT); 94 G.drawline (x1, y1, x2, y2); 95} 96} 97 98/** 99 * Draw random characters * @param g101 * @param createTypeFlag102 * @return1 * String ... createtypeflag is a mutable parameter, 104 * Java1.5 adds new features: variable parameters: For cases where the parameter number is indeterminate and the type is determined, Java handles the mutable parameter as an array. Note: mutable parameters must be in the last item */106 private String drawrandomnum (graphics2d g,string ... createtypeflag) {107//Set Color 108 G.setcolor (color.red); 109//Set font G.setfont (new font ("Arial", Font.Bold, 20)); 111//Common The Chinese character of the Basechinesechar String = "\u7684\u4e00\u4e86\u662f\u6211\u4e0d\u5728\u4eba\u4eec\u6709\u6765\u4ed6\u8fd9\u4e0a\u7740\u4e2a\u5730\u5230\u5927\u91cc\u8bf4\u5c31\u53bb\u5b50\ U5f97\u4e5f\u548c\u90a3\u8981\u4e0b\u770b\u5929\u65f6\u8fc7\u51fa\u5c0f\u4e48\u8d77\u4f60\u90fd\u628a\u597d\ U8fd8\u591a\u6ca1\u4e3a\u53c8\u53ef\u5bb6\u5b66\u53ea\u4ee5\u4e3b\u4f1a\u6837\u5e74\u60f3\u751f\u540c\u8001\ U4e2d\u5341\u4ece\u81ea\u9762\u524d\u5934\u9053\u5b83\u540e\u7136\u8d70\u5f88\u50cf\u89c1\u4e24\u7528\u5979\ u56fd\u52a8\u8fdb\u6210\u56de\u4ec0\u8fb9\u4f5c\u5bf9\u5f00\u800c\u5df1\u4e9b\u73b0\u5c71\u6c11\u5019\u7ecf\ U53d1\u5de5\u5411\u4e8b\u547d\u7ed9\u957f\u6c34\u51e0\u4e49\u4e09\u58f0\u4e8e\u9ad8\u624b\u77e5\u7406\u773c\ U5fd7\u70b9\u5fc3\u6218\u4e8c\u95ee\u4f46\u8eab\u65b9\u5b9e\u5403\u505a\u53eb\u5f53\u4f4f\u542c\u9769\u6253\ U5462\u771f\u5168\u624d\u56db\u5df2\u6240\u654c\u4e4b\u6700\u5149\u4ea7\u60c5\u8def\u5206\u603b\u6761\u767d\ U8bdd\u4e1c\u5e2d\u6b21\u4eb2\u5982\u88ab\u82b1\u53e3\u653e\u513f\u5e38\u6c14\u4e94\u7b2c\u4f7f\u5199\u519b\ U5427\u6587\u8fd0\u518d\u679c\U600e\u5b9a\u8bb8\u5feb\u660e\u884c\u56e0\u522b\u98de\u5916\u6811\u7269\u6d3b\u90e8\u95e8\u65e0\u5f80\u8239\ U671b\u65b0\u5e26\u961f\u5148\u529b\u5b8c\u5374\u7ad9\u4ee3\u5458\u673a\u66f4\u4e5d\u60a8\u6bcf\u98ce\u7ea7\ U8ddf\u7b11\u554a\u5b69\u4e07\u5c11\u76f4\u610f\u591c\u6bd4\u9636\u8fde\u8f66\u91cd\u4fbf\u6597\u9a6c\u54ea\ U5316\u592a\u6307\u53d8\u793e\u4f3c\u58eb\u8005\u5e72\u77f3\u6ee1\u65e5\u51b3\u767e\u539f\u62ff\u7fa4\u7a76\ U5404\u516d\u672c\u601d\u89e3\u7acb\u6cb3\u6751\u516b\u96be\u65e9\u8bba\u5417\u6839\u5171\u8ba9\u76f8\u7814\ U4eca\u5176\u4e66\u5750\u63a5\u5e94\u5173\u4fe1\u89c9\u6b65\u53cd\u5904\u8bb0\u5c06\u5343\u627e\u4e89\u9886\ U6216\u5e08\u7ed3\u5757\u8dd1\u8c01\u8349\u8d8a\u5b57\u52a0\u811a\u7d27\u7231\u7b49\u4e60\u9635\u6015\u6708\ U9752\u534a\u706b\u6cd5\u9898\u5efa\u8d76\u4f4d\u5531\u6d77\u4e03\u5973\u4efb\u4ef6\u611f\u51c6\u5f20\u56e2\ U5c4b\u79bb\u8272\u8138\u7247\u79d1\u5012\u775b\u5229\u4e16\u521a\u4e14\u7531\u9001\u5207\u661f\u5bfc\u665a\ u8868\u591f\u6574\u8ba4\u54cD\u96ea\u6d41\u672a\u573a\u8be5\u5e76\u5e95\u6df1\u523b\u5e73\u4f1f\u5fd9\u63d0\u786e\u8fd1\u4eae\u8f7b\u8bb2\ U519c\u53e4\u9ed1\u544a\u754c\u62c9\u540d\u5440\u571f\u6e05\u9633\u7167\u529e\u53f2\u6539\u5386\u8f6c\u753b\ U9020\u5634\u6b64\u6cbb\u5317\u5fc5\u670d\u96e8\u7a7f\u5185\u8bc6\u9a8c\u4f20\u4e1a\u83dc\u722c\u7761\u5174\ u5f62\u91cf\u54b1\u89c2\u82e6\u4f53\u4f17\u901a\u51b2\u5408\u7834\u53cb\u5ea6\u672f\u996d\u516c\u65c1\u623f\ U6781\u5357\u67aa\u8bfb\u6c99\u5c81\u7ebf\u91ce\u575a\u7a7a\u6536\u7b97\u81f3\u653f\u57ce\u52b3\u843d\u94b1\ U7279\u56f4\u5f1f\u80dc\u6559\u70ed\u5c55\u5305\u6b4c\u7c7b\u6e10\u5f3a\u6570\u4e61\u547c\u6027\u97f3\u7b54\ U54e5\u9645\u65e7\u795e\u5ea7\u7ae0\u5e2e\u5566\u53d7\u7cfb\u4ee4\u8df3\u975e\u4f55\u725b\u53d6\u5165\u5cb8\ U6562\u6389\u5ffd\u79cd\u88c5\u9876\u6025\u6797\u505c\u606f\u53e5\u533a\u8863\u822c\u62a5\u53f6\u538b\u6162\         U53D4\U80CC\U7EC6 "; 113//combination of numbers and letters, String basenumletter =" 0123456789ABCDEFGHJKLMNOPQRSTUVWXYZ "; 115 Pure Number 116         String basenum = "0123456789"; 117//plain Letter 118 String baseletter = "abcdefghjklmnopqrstuvwxyz"; 119 Createtypeflag[0]==null indicates that no parameters are passed if (createtypeflag.length > 0 && null! = Createtypeflag[0]) {121 if (createtypeflag[0].equals ("ch")) {122//intercept Kanji 123 return CREATERANDOMCH                 AR (g, Basechinesechar); 124}else if (createtypeflag[0].equals ("NL")) {125//intercept number and letter combinations 126                 Return Createrandomchar (g, basenumletter); 127}else if (Createtypeflag[0].equals ("n")) {128 Intercept the number 129 return Createrandomchar (g, basenum);}else if (Createtypeflag[0].equa         LS ("L")) {131//intercept letter Createrandomchar (g, baseletter); 133}134         }else {135//default intercept combination of numbers and letters 136 return Createrandomchar (g, basenumletter); 137}138 139 Return "";140}141 142/**143 * Create random characters 144 * @param g145 * @param baseChar146 * @return Random characters 147 */14         8 Private String Createrandomchar (graphics2d g,string basechar) {149 StringBuffer sb = new StringBuffer (); 150             int x = 5;151 String ch = ""; 152//Control word 153 for (int i = 0; i < 4; i++) {154 Set font rotation angle 155 int degree = new random (). Nextint ()% 30;156 ch = basechar.charat (new random (). NEX TInt (Basechar.length ())) + "", 157 sb.append (CH), 158//Positive angle 159 g.rotate (Degree * Math).  pi/180, X, g.drawstring (CH, x, 20), 161//Reverse Angle 162 g.rotate (-degree * Math.PI 163 x + = 30;164}165 return sb.tostring (); 166}167}

The results of the operation are as follows:

　　

Second, use the Verification code picture in form form

 1 <%@ page language= "java" import= "java.util.*" pageencoding= "UTF-8"%> 2 <! DOCTYPE HTML PUBLIC "-//w3c//dtd HTML 4.01 transitional//en" > 3 
Operation Result:
　　
DrawImage servlet In addition to the combination of letters and numbers can generate a code picture, you can also generate Chinese characters, pure numbers, pure letters of the verification Code picture, just to the DrawImage Servlet pass the agreed-upon generation identifier parameters, as follows:
 1 <%@ page language= "java" import= "java.util.*" pageencoding= "UTF-8"%> 2 <! DOCTYPE HTML PUBLIC "-//w3c//dtd HTML 4.01 transitional//en" > 3 
The results of the operation are as follows:
　　
third, the server side of the form form submitted by the Verification Code processing
 1 package gacl.response.study; 2 Import java.io.IOException; 3 Import javax.servlet.ServletException; 4 Import Javax.servlet.http.HttpServlet; 5 Import Javax.servlet.http.HttpServletRequest; 6 Import Javax.servlet.http.HttpServletResponse; 7/** 8 * @author gacl 9 * Processing after the server has received the Verification Code */11 public class Checkservlet extends HttpServlet {gb public void DoGe         T (httpservletrequest request, httpservletresponse response) throws Servletexception, IOException {14 String clientcheckcode = Request.getparameter ("Validatecode");//receive the verification code submitted by the client browser, string servercheckcode = (stri ng) Request.getsession (). getattribute ("Checkcode");//Remove the CAPTCHA from the server-side session (Clientcheckcode.equals (Servercheck Code) {//compares the client and server-side validations, if equal, means that the validation passes through the SYSTEM.OUT.PRINTLN ("Verification Code Verification pass!"). ");}else {System.out.println (" Verification Code verification failed!             ");}21}22 DoPost (httpservletrequest request, httpservletresponse response) 24 ThRows Servletexception, IOException {doget (request, response); 26}27 28} 
Javaweb Learning Summary (ix)-Generate a CAPTCHA image from a servlet