<div style="margin-top: 50px;">
  <span>驗(yàn)證碼：</span><input type="text" name="verifyCode" id="verifyCode" style="width: 75px;height: 25px;"/>
  <img id="verifyCodeImg" alt="點(diǎn)擊更換" src="/qos/dog/getVerifyCodeImg"
   title="點(diǎn)擊更換" onclick="change()">
</div>

function change() {
  var verifyCode = document.getElementById("verifyCodeImg");
  verifyCode.src = "/qos/dog/getVerifyCodeImg?time=" + Math.random(1000);
 }
 
/*-*/
 
/qos/dog/ 這里的路徑是需要換成自己的哦 

package com.paladin.qos.util;
 
import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.Random;
 
public class VerifyCodeUtil {
 
 private static final Random random = new Random();
 private static final String[] fontNames = {"宋體", "華文楷體", "黑體", "Georgia", "微軟雅黑", "楷體_GB2312"};
 
 public static String drawImage(ByteArrayOutputStream output) {
  String code = "";
  int width = 50;
  int height = 25;
 
  //創(chuàng)建圖片緩沖區(qū)
  BufferedImage bi = new BufferedImage(width, height, BufferedImage.TYPE_3BYTE_BGR);
 
  Graphics2D g = bi.createGraphics();
 
  //設(shè)置背景顏色
  g.setBackground(new Color(255, 255, 255));
  g.clearRect(0, 0, width, height);
 
  StringBuilder stringBuilder = new StringBuilder();
  //這里只畫(huà)入四個(gè)字符
  for (int i = 0; i < 4; i++) {
   String s = randomChar() + "";  //隨機(jī)生成字符，因?yàn)橹挥挟?huà)字符串的方法，沒(méi)有畫(huà)字符的方法，所以需要將字符變成字符串再畫(huà)
   stringBuilder.append(s);   //添加到StringBuilder里面
   float x = i * 1.0F * width / 4; //定義字符的x坐標(biāo)
   g.setFont(randomFont());   //設(shè)置字體，隨機(jī)
   g.setColor(randomColor());   //設(shè)置顏色，隨機(jī)
   g.drawString(s, x, height - 5);
  }
  code = stringBuilder.toString();//獲取驗(yàn)證碼字符串
 
  //定義干擾線
  //定義干擾線的數(shù)量（3-5條）int num = random.nextInt(max)%(max-min+1) + min;
  int num = random.nextInt(5) % 3 + 3;
  Graphics2D graphics = (Graphics2D) bi.getGraphics();
  for (int i = 0; i < num; i++) {
   int x1 = random.nextInt(width);
   int y1 = random.nextInt(height);
   int x2 = random.nextInt(width);
   int y2 = random.nextInt(height);
   graphics.setColor(randomColor());
   graphics.drawLine(x1, y1, x2, y2);
  }
  // 釋放圖形上下文
  g.dispose();
  try {
   ImageIO.write(bi, "jpg", output);
  } catch (IOException e) {
   e.printStackTrace();
  }
  return code;//為了方便取值，直接返回code，
 
 
 
 }
 
 //隨機(jī)字體
 private static Font randomFont() {
  int index = random.nextInt(fontNames.length);
  String fontName = fontNames[index];
  int style = random.nextInt(4);   //隨機(jī)獲取4種字體的樣式
  int size = random.nextInt(20) % 6 + 15; //隨機(jī)獲取字體的大小(10-20之間的值)
  return new Font(fontName, style, size);
 }
 
 //隨機(jī)顏色
 private static Color randomColor() {
  int r = random.nextInt(225);
  int g = random.nextInt(225);
  int b = random.nextInt(225);
  return new Color(r, g, b);
 }
 
 
 //隨機(jī)字符
 private static char randomChar() {
  //A-Z,a-z,0-9,可剔除一些難辨認(rèn)的字母與數(shù)字
  String str = "0123456789ABCdefghiDEFGHIJopPQRVWXYZabcjklSTUmnqrstKLMNOvuwxyz";
 
  return str.charAt(random.nextInt(str.length()));
 }
 
}

@RequestMapping("/getVerifyCodeImg")
@ResponseBody

public void getVerifyCodeImg(HttpServletResponse response, HttpSession session) {
  ByteArrayOutputStream output = new ByteArrayOutputStream();
  String code = VerifyCodeUtil.drawImage(output);
  //將驗(yàn)證碼文本直接存放到session中
  session.setAttribute("verifyCode", code);
  try {
   ServletOutputStream out = response.getOutputStream();
   output.writeTo(out);
  } catch (IOException e) {
   e.printStackTrace();
  }
 }