/**
 * 生成驗(yàn)證碼的工具類(lèi)
 */
public class VerifyCode {

	private int width = 100;// 生成驗(yàn)證碼圖片的寬度
	private int height = 50;// 生成驗(yàn)證碼圖片的高度
	private String[] fontNames = { "宋體", "楷體", "隸書(shū)", "微軟雅黑" };
	private Color bgColor = new Color(255, 255, 255);// 定義驗(yàn)證碼圖片的背景顏色為白色
	private Random random = new Random();
	private String codes = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
	private String text;// 記錄隨機(jī)字符串

	/**
	 * 獲取一個(gè)隨意顏色
	 * 
	 * @return
	 */
	private Color randomColor() {
		int red = random.nextInt(150);
		int green = random.nextInt(150);
		int blue = random.nextInt(150);
		return new Color(red, green, blue);
	}

	/**
	 * 獲取一個(gè)隨機(jī)字體
	 * 
	 * @return
	 */
	private Font randomFont() {
		String name = fontNames[random.nextInt(fontNames.length)];
		int style = random.nextInt(4);
		int size = random.nextInt(5) + 24;
		return new Font(name, style, size);
	}

	/**
	 * 獲取一個(gè)隨機(jī)字符
	 * 
	 * @return
	 */
	private char randomChar() {
		return codes.charAt(random.nextInt(codes.length()));
	}

	/**
	 * 創(chuàng)建一個(gè)空白的BufferedImage對(duì)象
	 * 
	 * @return
	 */
	private BufferedImage createImage() {
		BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
		Graphics2D g2 = (Graphics2D) image.getGraphics();
		g2.setColor(bgColor);// 設(shè)置驗(yàn)證碼圖片的背景顏色
		g2.fillRect(0, 0, width, height);
		return image;
	}

	public BufferedImage getImage() {
		BufferedImage image = createImage();
		Graphics2D g2 = (Graphics2D) image.getGraphics();
		StringBuffer sb = new StringBuffer();
		for (int i = 0; i < 4; i++) {
			String s = randomChar() + "";
			sb.append(s);
			g2.setColor(randomColor());
			g2.setFont(randomFont());
			float x = i * width * 1.0f / 4;
			g2.drawString(s, x, height - 15);
		}
		this.text = sb.toString();
		drawLine(image);
		return image;
	}

	/**
	 * 繪制干擾線(xiàn)
	 * 
	 * @param image
	 */
	private void drawLine(BufferedImage image) {
		Graphics2D g2 = (Graphics2D) image.getGraphics();
		int num = 5;
		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);
			g2.setColor(randomColor());
			g2.setStroke(new BasicStroke(1.5f));
			g2.drawLine(x1, y1, x2, y2);
		}
	}

	public String getText() {
		return text;
	}

	public static void output(BufferedImage image, OutputStream out) throws IOException {
		ImageIO.write(image, "JPEG", out);
	}
}

@RestController
public class VerifyCodeController {
 @GetMapping("/vercode")
 public void code(HttpServletRequest req, HttpServletResponse resp) throws IOException {
  VerifyCode vc = new VerifyCode();
  BufferedImage image = vc.getImage();
  String text = vc.getText();
  HttpSession session = req.getSession();
  session.setAttribute("index_code", text);
  VerifyCode.output(image, resp.getOutputStream());
 }
}

<img src="/vercode" alt="">

@Component
public class VerifyCodeFilter extends GenericFilterBean {
 private String defaultFilterProcessUrl = "/doLogin";

 @Override
 public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain)
   throws IOException, ServletException {
  HttpServletRequest request = (HttpServletRequest) req;
  HttpServletResponse response = (HttpServletResponse) res;
  if ("POST".equalsIgnoreCase(request.getMethod()) && defaultFilterProcessUrl.equals(request.getServletPath())) {
   // 驗(yàn)證碼驗(yàn)證
   String requestCaptcha = request.getParameter("code");
   String genCaptcha = (String) request.getSession().getAttribute("index_code");
   if (StringUtils.isEmpty(requestCaptcha))
    throw new AuthenticationServiceException("驗(yàn)證碼不能為空!");
   if (!genCaptcha.toLowerCase().equals(requestCaptcha.toLowerCase())) {
    throw new AuthenticationServiceException("驗(yàn)證碼錯(cuò)誤!");
   }
  }
  chain.doFilter(request, response);
 }
}

@Configuration
public class SecurityConfig extends WebSecurityConfigurerAdapter {

 @Autowired
 VerifyCodeFilter verifyCodeFilter;
 ...
 ...
 @Override
 protected void configure(HttpSecurity http) throws Exception {
  http.addFilterBefore(verifyCodeFilter, UsernamePasswordAuthenticationFilter.class);
  http.authorizeRequests()
    .antMatchers("/admin/**").hasRole("admin")
    ...
    ...
    .permitAll()
    .and()
    .csrf().disable();
 }
}