Servlet Case 3: verification code function, servlet case 3 Verification Code

Servlet Case 3: verification code function, servlet case 3 Verification Code

Here we will introduce the simple verification code function.

Dynamic Image Generation

 

A simple page:

<! DOCTYPE html> View Code
Simple JS Code to achieve click Verification Code image refresh
 
Verification Code function:
Package demo; import java. awt. color; import java. awt. font; import java. awt. graphics; import java. awt. graphics2D; import java. awt. image. bufferedImage; import java. io. bufferedReader; import java. io. fileReader; import java. io. IOException; import java. util. arrayList; import java. util. list; import java. util. random; import javax. imageio. imageIO; import javax. servlet. servletException; import javax. servlet. http. httpServ Let; import javax. servlet. http. httpServletRequest; import javax. servlet. http. httpServletResponse; /*** Verification Code Generation Program ***/public class CheckImgServlet extends HttpServlet {// Save All idioms in the set private List <String> words = new ArrayList <String> (); @ Override public void init () throws ServletException {// reading the stage, read new_words.txt // read the file from the web project, and use the absolute disk path String path = getServletContext (). getRealPath ("/WEB-INF/new _Words.txt "); try {BufferedReader reader = new BufferedReader (new FileReader (path); String line; while (line = reader. readLine ())! = Null) {words. add (line);} reader. close ();} catch (IOException e) {e. printStackTrace () ;}} public void doGet (HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {// disable caching // response. setHeader ("Cache-Control", "no-cache"); // response. setHeader ("Pragma", "no-cache"); // response. setDateHeader ("Expires",-1); int width = 120; int height = 30; // Step 1: Draw a buffer image BufferedImage bufferedImage = new BufferedImage (width, height, bufferedImage. TYPE_INT_RGB); // Step 2. Draw the background color through the Drawing Object Graphics graphics = bufferedImage. getGraphics (); // get the Drawing Object --- paint brush // you must specify a color graphics before drawing any image. setColor (getRandColor (200,250); graphics. fillRect (0, 0, width, height); // draw the border graphics in step 3. setColor (Color. WHITE); graphics. drawRect (0, 0, width-1, height-1); // Step 4: Graphics2D graphics2d = (Graphics2D) graphics; // set the output font graphics2d. setFont (new Font ("", Font. BOLD, 18); Random random = new Random (); // generate random number int index = Random. nextInt (words. size (); String word = words. get (index); // get the idiom // define the x coordinate int x = 10; for (int I = 0; I <word. length (); I ++) {// random color graphics2d. setColor (new Color (20 + random. nextInt (110), 20 + random. nextInt (110), 20 + random. nextInt (110); // rotate-30 --- 30 degrees int jiaodu = random. nextInt (60)-30; // converts the radian double theta = jiaodu * Math. PI/180; // obtain the alphanumeric char c = word. charAt (I); // Output c to graphics2d. rotate (theta, x, 20); graphics2d. drawString (String. valueOf (c), x, 20); graphics2d. rotate (-theta, x, 20); x + = 30;} // Save the verification code to the session request. getSession (). setAttribute ("checkcode_session", word); // draw the interference Line graphics in step 5. setColor (getRandColor (160,200); int x1; int x2; int y1; int y2; for (int I = 0; I <30; I ++) {x1 = random. nextInt (width); x2 = random. nextInt (12); y1 = random. nextInt (height); y2 = random. nextInt (12); graphics. drawLine (x1, y1, x1 + x2, x2 + y2);} // output the image above to the browser ImageIO graphics. dispose (); // release the resource // write the image to response. imageIO in getOutputStream. write (bufferedImage, "jpg", response. getOutputStream ();} public void doPost (HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {doGet (request, response );} /*** obtain the color of a specific range ** @ param fc * int range parameter 1 * @ param bc * int range parameter 2 * @ return Color */private Color getRandColor (int fc, int bc) {// obtain the Random color random Random = new Random (); if (fc> 255) {fc = 255;} if (bc> 255) {bc = 255;} int r = fc + random. nextInt (bc-fc); int g = fc + random. nextInt (bc-fc); int B = fc + random. nextInt (bc-fc); return new Color (r, g, B );}}
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Here is the idiom verification code, will be a lot of idioms stored in the WEB-INF directory of the next text, each line of one can be
 
Add the web. xml configuration file
<?xml version="1.0" encoding="UTF-8"?><web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">  <display-name>WEB4</display-name>  <welcome-file-list>    <welcome-file>index.html</welcome-file>    <welcome-file>index.htm</welcome-file>    <welcome-file>index.jsp</welcome-file>    <welcome-file>default.html</welcome-file>    <welcome-file>default.htm</welcome-file>    <welcome-file>default.jsp</welcome-file>  </welcome-file-list>  <servlet>    <description></description>    <display-name>CheckImgServlet</display-name>    <servlet-name>CheckImgServlet</servlet-name>    <servlet-class>demo.CheckImgServlet</servlet-class>  </servlet>  <servlet-mapping>    <servlet-name>CheckImgServlet</servlet-name>    <url-pattern>/checkImg</url-pattern>  </servlet-mapping></web-app>
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