本文實例為大家分享了Java隨機生成驗證碼的具體代碼，供大家參考，具體內容如下
import java.awt.Color;import java.awt.Font;import java.awt.Graphics2D;import java.awt.image.BufferedImage;import java.io.IOException;import java.util.Random;import javax.imageio.ImageIO;import javax.servlet.ServletException;import javax.servlet.ServletOutputStream;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import javax.servlet.http.HttpSession;public class RandImage extends HttpServlet {/*** Constructor of the object.*/ public RandImage() { super(); } private int imgWidth = 0; //圖片寬度private int imgHeight = 0; //圖片的高度private int codeCount = 0; //圖片裡面字符的個數private int x = 0; private int fontHeight; //字體的高度private int codeY; private String fontStyle; //字體樣式//序列化ID 避免重複private static final long serialVersionUID = 128554012633034503L; /** * 初始化配置參數*/public void init() throws ServletException { // 寬度String strWidth = "200"; // 高度String strHeight ="80"; // 字符個數String strCodeCount ="5"; //字體fontStyle = "Times New Roman";// 將配置的信息轉換成數值try { if (strWidth != null && strWidth.length() != 0) { imgWidth = Integer.parseInt(strWidth); } if (strHeight != null && strHeight.length() != 0) { imgHeight = Integer.parseInt(strHeight); } if (strCodeCount != null && strCodeCount.length() != 0) { codeCount = Integer.parseInt(strCodeCount); } } catch (NumberFormatException e) { e.printStackTrace(); } x = imgWidth / (codeCount + 1); //字符間距fontHeight = imgHeight - 2; //字體的高度codeY = imgHeight - 12; // 代碼高度} protected void processRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //輸出流設置response.setContentType("image/jpeg"); //輸出格式response.setHeader("Pragma", "No-cache");//不緩存重新生成response.setHeader("Cache-Control", "no-cache");//不緩存重新生成response.setDateHeader("Expires", 0); //0秒失效也是不緩存HttpSession session = request.getSession(); //獲取session 會話// 在內存中創建圖像BufferedImage image = new BufferedImage(imgWidth, imgHeight, BufferedImage.TYPE_INT_RGB); // 獲取圖形上下文Graphics2D g = image.createGraphics(); // 生成隨機類Random random = new Random(); //隨機類// 設定矩形的背景色g.setColor(Color.WHITE); //填充矩形Rect為白色g.fillRect(0, 0, imgWidth, imgHeight); // 設定邊框字體g.setFont(new Font(fontStyle, Font.PLAIN + Font.ITALIC, fontHeight)); //設置邊框的顏色g.setColor(new Color(55, 55, 12)); // 畫邊框g.drawRect(0, 0, imgWidth - 1, imgHeight - 1); // 隨機產生160條干擾線，使圖像中的認證碼不易被其它程序探測到g.setColor(getRandColor(160, 200)); for (int i = 0; i < 160; i++) { int x = random.nextInt(imgWidth); int y = random.nextInt(imgHeight); int xl = random.nextInt(12); int yl = random.nextInt(12); g.drawLine(x, y, x + xl, y + yl); } // 取隨機產生的認證碼(4位數字) String sRand = ""; int red = 0, green = 0, blue = 0; for (int i = 0; i < codeCount; i++) { //循環生成codeCount個隨機字符//通過rgb三色隨機得到新的顏色red = random.nextInt(255); green = random.nextInt(255); blue = random.nextInt(255); //隨機得到一個0 1 2 的數字int wordType = random.nextInt(3);//隨機得到0-2之間的3個數字char retWord = 0; //0 數字1 小寫字母2 大寫字母switch (wordType) { case 0: retWord = this.getSingleNumberChar(); //得到0-9的char型數字break; case 1: retWord = this.getLowerOrUpperChar(0); //得到小寫的char型字母break; case 2: retWord = this.getLowerOrUpperChar(1); //得到大寫的char型字母break; } sRand += String.valueOf(retWord); //將得到的隨機字符連接起來g.setColor(new Color(red, green, blue)); //設置一個顏色g.drawString(String.valueOf(retWord), 2+(i) * x, codeY); //將字符寫到圖片中對應的位置} // 將認證碼存入SESSION session.setAttribute("rand", sRand); //將得到的隨機字符存入到session回話中，驗證的時候可以調用// 圖像生效g.dispose(); //釋放g 對象ServletOutputStream responseOutputStream = response.getOutputStream(); //輸出流// 輸出圖像到頁面ImageIO.write(image, "JPEG", responseOutputStream); //以JPEG的格式輸出// 以下關閉輸入流！ responseOutputStream.flush();//刷新並關閉流responseOutputStream.close(); } Color getRandColor(int fc, int bc) {// 給定範圍獲得隨機顏色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); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { processRequest(request, response); } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { processRequest(request, response); } // 將整型隨機數字轉換成char返回private char getSingleNumberChar() { Random random = new Random(); int numberResult = random.nextInt(10); int ret = numberResult + 48; //將字符'0' 轉換成ascall碼的時候就是48 return (char) ret; } //得到26個字符private char getLowerOrUpperChar(int upper) { Random random = new Random(); int numberResult = random.nextInt(26); int ret = 0; if (upper == 0) {// 小寫ret = numberResult + 97; } else if (upper == 1) {// 大寫ret = numberResult + 65; } return (char) ret; }}以上就是本文的全部內容，希望對大家的學習有所幫助，也希望大家多多支持武林網。