验证码生成与异步刷新

Spring mvc 部分代码

@RequestMapping(value = "/getAuthImg", method = RequestMethod.GET)
	@ResponseBody
	public void getAuthImg(HttpServletResponse response) throws IOException {
		new AuthImg().service(response);
	}

验证码生成代码 AuthImg.java ，将生成的验证码的码值放在了session中(这是shiro的部分代码，所以session获取是通过SecurityUtils.getSubject().getSession()得到的)

package com.util;

import javax.servlet.http.*;
import java.io.*;
import java.awt.*;
import java.awt.image.*;
import java.util.*;
import javax.imageio.*;
import org.apache.shiro.SecurityUtils;

public class AuthImg {
	//设置字体
	private final Font mFont = new Font("Arial Black", Font.PLAIN, 21);
	private final int IMG_WIDTH = 75;
	private final int IMG_HEIGTH = 36;

	public void service( HttpServletResponse response) throws IOException {
		response.setHeader("Pragma", "No-cache");
		response.setHeader("Cache-Control", "no-cache");
		response.setDateHeader("Expires", 0);
		response.setContentType("image/jpeg");
		BufferedImage image = new BufferedImage(IMG_WIDTH, IMG_HEIGTH, BufferedImage.TYPE_INT_RGB);
		Graphics g = image.getGraphics();
		Random random = new Random();
		g.setColor(getRandColor(200, 250));
		g.fillRect(1, 1, IMG_WIDTH - 1, IMG_HEIGTH - 1);
		g.setColor(new Color(102, 102, 102));
		g.drawRect(0, 0, IMG_WIDTH - 1, IMG_HEIGTH - 1);
		g.setColor(getRandColor(160, 200));
		for (int i = 0; i < 30; i++) {
			int x = random.nextInt(IMG_WIDTH - 1);
			int y = random.nextInt(IMG_HEIGTH - 1);
			int xl = random.nextInt(6) + 1;
			int yl = random.nextInt(12) + 1;
			g.drawLine(x, y, x + xl, y + yl);
		}
		g.setColor(getRandColor(160, 200));
		for (int i = 0; i < 30; i++) {
			int x = random.nextInt(IMG_WIDTH - 1);
			int y = random.nextInt(IMG_HEIGTH - 1);
			int xl = random.nextInt(12) + 1;
			int yl = random.nextInt(6) + 1;
			g.drawLine(x, y, x - xl, y - yl);
		}
		g.setFont(mFont);
		String sRand = "";
		for (int i = 0; i < 4; i++) {
			String tmp = getRandomChar();
			sRand += tmp;
			g.setColor(new Color(20 + random.nextInt(110), 20 + random.nextInt(110), 20 + random.nextInt(110)));
			//设置字体位置
			g.drawString(tmp, 15 * i + 11, 25);
		}
		SecurityUtils.getSubject().getSession().setAttribute("rand", sRand);
		g.dispose();
		ImageIO.write(image, "JPEG", response.getOutputStream());
	}

	private String getRandomChar() {
		int rand = (int) Math.round(Math.random() * 2);
		long itmp = 0;
		char ctmp = '\u0000';
		switch (rand) {
		case 1:
			itmp = Math.round(Math.random() * 25 + 65);
			ctmp = (char) itmp;
			return String.valueOf(ctmp);
		case 2:
			itmp = Math.round(Math.random() * 25 + 97);
			ctmp = (char) itmp;
			return String.valueOf(ctmp);
		default:
			itmp = Math.round(Math.random() * 9);
			return itmp + "";
		}
	}

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

显示部分

<img src="getAuthImg" id="AuthImg">

js动态修改部分，防止浏览器缓存，加入一个时间属性

$('#AuthImg').on('click', function() {
				var timestamp = new Date().getTime();
				$(this).attr("src", $("#AuthImg").attr('src') + '?' + timestamp);
			});