设置session验证码有效时间，定时删除session中的验证码

contorller.java

import java.util.Timer;
import java.util.TimerTask;


import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;


import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;


import com.yasinyt.loan.admin.util.VerifyCodeUtils;




@Controller
@RequestMapping("sys/yzm")
public class YZMController {


	private Logger log = LoggerFactory.getLogger(YZMController.class);


	@RequestMapping(value = "getYzm", method = RequestMethod.GET)
	public void getYzm(HttpServletResponse response, HttpServletRequest request) {
		try {
			response.setHeader("Pragma", "No-cache");
			response.setHeader("Cache-Control", "no-cache");
			response.setDateHeader("Expires", 0);
			response.setContentType("image/jpeg");
			// 生成随机字串
			String verifyCode = VerifyCodeUtils.generateVerifyCode(4);
			// 存入会话session
			HttpSession session = request.getSession(true);
			String attrName = "_code";
			session.setAttribute(attrName, verifyCode.toLowerCase());
			// 生成验证码流
			int w = 99, h = 38;
			VerifyCodeUtils.outputImage(w, h, response.getOutputStream(), verifyCode);
			//定时5分钟删除验证码
			this.removeAttrbute(session, attrName);
		} catch (Exception e) {
			log.error("获取验证码异常：{}",e.getCause().toString());
		}
	}
	
	/**
	 * 设置5分钟后删除session中的验证码
	 * @param session
	 * @param attrName
	 */
	private void removeAttrbute(final HttpSession session, final String attrName) {
		final Timer timer = new Timer();
		timer.schedule(new TimerTask() {
			@Override
			public void run() {
				// 删除session中存的验证码
				session.removeAttribute(attrName);
				timer.cancel();
			}
		}, 5 * 60 * 1000);
	}
}

VerifyCodeUtils.java

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Arrays;
import java.util.Random;

import javax.imageio.ImageIO;

public class VerifyCodeUtils {

	// 使用到Algerian字体，系统里没有的话需要安装字体，字体只显示大写，去掉了1,0,i,o几个容易混淆的字符
	public static final String VERIFY_CODES = "23456789ABCDEFGHJKLMNPQRSTUVWXYZ";
	private static Random random = new Random();

	/**
	 * 使用系统默认字符源生成验证码
	 * 
	 * @param verifySize
	 *            验证码长度
	 * @return
	 */
	public static String generateVerifyCode(int verifySize) {
		return generateVerifyCode(verifySize, VERIFY_CODES);
	}

	/**
	 * 使用指定源生成验证码
	 * 
	 * @param verifySize
	 *            验证码长度
	 * @param sources
	 *            验证码字符源
	 * @return
	 */
	public static String generateVerifyCode(int verifySize, String sources) {
		if (sources == null || sources.length() == 0) {
			sources = VERIFY_CODES;
		}
		int codesLen = sources.length();
		Random rand = new Random(System.currentTimeMillis());
		StringBuilder verifyCode = new StringBuilder(verifySize);
		for (int i = 0; i < verifySize; i++) {
			verifyCode.append(sources.charAt(rand.nextInt(codesLen - 1)));
		}
		return verifyCode.toString();
	}

	/**
	 * 生成随机验证码文件,并返回验证码值
	 * 
	 * @param w
	 * @param h
	 * @param outputFile
	 * @param verifySize
	 * @return
	 * @throws IOException
	 */
	public static String outputVerifyImage(int w, int h, File outputFile, int verifySize) throws IOException {
		String verifyCode = generateVerifyCode(verifySize);
		outputImage(w, h, outputFile, verifyCode);
		return verifyCode;
	}

	/**
	 * 输出随机验证码图片流,并返回验证码值
	 * 
	 * @param w
	 * @param h
	 * @param os
	 * @param verifySize
	 * @return
	 * @throws IOException
	 */
	public static String outputVerifyImage(int w, int h, OutputStream os, int verifySize) throws IOException {
		String verifyCode = generateVerifyCode(verifySize);
		outputImage(w, h, os, verifyCode);
		return verifyCode;
	}

	/**
	 * 生成指定验证码图像文件
	 * 
	 * @param w
	 * @param h
	 * @param outputFile
	 * @param code
	 * @throws IOException
	 */
	public static void outputImage(int w, int h, File outputFile, String code) throws IOException {
		if (outputFile == null) {
			return;
		}
		File dir = outputFile.getParentFile();
		if (!dir.exists()) {
			dir.mkdirs();
		}
		try {
			outputFile.createNewFile();
			FileOutputStream fos = new FileOutputStream(outputFile);
			outputImage(w, h, fos, code);
			fos.close();
		} catch (IOException e) {
			throw e;
		}
	}

	/**
	 * 输出指定验证码图片流
	 * 
	 * @param w
	 * @param h
	 * @param os
	 * @param code
	 * @throws IOException
	 */
	public static void outputImage(int w, int h, OutputStream os, String code) throws IOException {
		int verifySize = code.length();
		BufferedImage image = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
		Random rand = new Random();
		Graphics2D g2 = image.createGraphics();
		g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
		Color[] colors = new Color[5];
		Color[] colorSpaces = new Color[] { Color.BLACK, Color.CYAN, Color.GRAY, Color.LIGHT_GRAY, Color.MAGENTA,
				Color.ORANGE, Color.PINK, Color.YELLOW };
		float[] fractions = new float[colors.length];
		for (int i = 0; i < colors.length; i++) {
			colors[i] = colorSpaces[rand.nextInt(colorSpaces.length)];
			fractions[i] = rand.nextFloat();
		}
		Arrays.sort(fractions);

		g2.setColor(Color.WHITE);// 设置边框色
		g2.fillRect(0, 0, w, h);

		Color c = getRandColor(150, 250);
		g2.setColor(c);// 设置背景色
//		g2.fillRect(0, 2, w, h - 4);

		// 绘制干扰线
		Random random = new Random();
		g2.setColor(getRandColor(160, 200));// 设置线条的颜色
		for (int i = 0; i < 20; i++) {
			int x = random.nextInt(w - 1);
			int y = random.nextInt(h - 1);
			int xl = random.nextInt(6) + 1;
			int yl = random.nextInt(12) + 1;
			g2.drawLine(x, y, x + xl + 40, y + yl + 20);
		}

		//添加噪点
		float yawpRate = 0.05f;// 噪声率
		int area = (int) (yawpRate * w * h);
		for (int i = 0; i < area; i++) {
			int x = random.nextInt(w);
			int y = random.nextInt(h);
			int rgb = getRandomIntColor();
			image.setRGB(x, y, rgb);
		}

//		shear(g2, w, h, c);// 使图片扭曲

		g2.setColor(getRandColor(100, 160));
		int fontSize = h - 6;
		Font font = new Font("Arial", Font.BOLD, fontSize);
		g2.setFont(font);
		char[] chars = code.toCharArray();
		for (int i = 0; i < verifySize; i++) {
			AffineTransform affine = new AffineTransform();
			affine.setToRotation(Math.PI / 4 * rand.nextDouble() * (rand.nextBoolean() ? 1 : -1),
					(w / verifySize) * i + fontSize / 2, h / 2);
			g2.setTransform(affine);
			g2.drawChars(chars, i, 1, ((w - 10) / verifySize) * i + 5, h / 2 + fontSize / 2 - 10);
		}

		g2.dispose();
		ImageIO.write(image, "jpg", os);
	}

	private static Color getRandColor(int fc, int bc) {
		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);
	}

	private static int getRandomIntColor() {
		int[] rgb = getRandomRgb();
		int color = 0;
		for (int c : rgb) {
			color = color << 8;
			color = color | c;
		}
		return color;
	}

	private static int[] getRandomRgb() {
		int[] rgb = new int[3];
		for (int i = 0; i < 3; i++) {
			rgb[i] = random.nextInt(255);
		}
		return rgb;
	}
}