JAVA实现验证码的功能

前台页面

java类

package com.lj.action;

import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Shape;
import java.awt.geom.Arc2D;
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 PictureCheckCode extends HttpServlet {

	private static final long serialVersionUID = -3235816079841410231L;

	// 该方法主要作用是获得随机生成的颜色
	public Color getRandColor() {
		Random r = new Random();
		Color c = new Color(r.nextInt(255), r.nextInt(255), r.nextInt(255));
		return c;
	}

	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		// TODO Auto-generated method stub
		this.doGet(req, resp);
	}

	@Override
	protected void doGet(HttpServletRequest request,
			HttpServletResponse response) throws ServletException, IOException {
		// 设置验证码的宽度和高度
		int width = 160, height = 50;
		// 创建BufferedImage对象,想到于一张画布
		BufferedImage image = new BufferedImage(width, height,
				BufferedImage.TYPE_INT_RGB);
		// 创建Graphics对象,相当于画笔
		Graphics g = image.getGraphics();
		// 创建Grapchics2D对象
		Graphics2D g2d = (Graphics2D) g;
		Random random = new Random();
		// 定义字体样式
		Font mfont = new Font("楷体", Font.BOLD, 40);
		g.setColor(getRandColor());
		// 绘制背景
		g.fillRect(0, 0, width, height);
		// 设置字体
		g.setFont(mfont);
		g.setColor(getRandColor());

		// 绘制1条曲线作为干扰线,该线条为2f
		BasicStroke bs = new BasicStroke(2f, BasicStroke.CAP_BUTT,
				BasicStroke.JOIN_BEVEL); // 定制线条样式
		Shape arc = new Arc2D.Float(10, 20, 150, 150, 40, 100, Arc2D.OPEN);
		g2d.setStroke(bs);
		g2d.draw(arc);

		// 输出由英文，数字，和中文随机组成的验证文字，具体的组合方式根据生成随机数确定。
		String sRand = "";
		String ctmp = "";
		int itmp = 0;
		// 制定输出的验证码为四位
		for (int i = 0; i < 4; i++) {
			switch (random.nextInt(2)) {
			case 1: // 生成A-Z的字母
				itmp = random.nextInt(26) + 65;
				ctmp = String.valueOf((char) itmp);
				break;
			default:
				itmp = random.nextInt(10) + 48;
				ctmp = String.valueOf((char) itmp);
				break;
			}
			sRand += ctmp;
			Color color = new Color(20 + random.nextInt(110), 20 + random
					.nextInt(110), random.nextInt(110));
			g.setColor(color);
			// 绘制文字
			g.drawString(ctmp, 30 * i + 20, 35);
		}

		// 把生成的文字放到session中
		HttpSession session = request.getSession(true);
		session.setAttribute("code", sRand);
		System.out.println(session.getAttribute("code"));
		g.dispose(); // 释放g所占用的系统资源

		// 设置不缓存图片
		response.setHeader("Pragma", "No-cache");
		response.setHeader("Cache-Control", "No-cache");
		response.setDateHeader("Expires", 0);
		// 指定生成的响应图片,一定不能缺少这句话,否则错误.
		response.setContentType("image/jpeg");
		ServletOutputStream sos = response.getOutputStream();
		ImageIO.write(image, "jpeg", sos);
		sos.close();
	}
}

判断验证码的类

package com.lj.action;

import java.io.IOException;
import java.io.OutputStream;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class LoginCheck extends HttpServlet {

	
	/**
	 * 判断验证码
	 */
	@Override
	protected void doGet(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		resp.setContentType("text/html; charset=UTF-8");//转码
		//得到项目路径
		String basePath = req.getScheme()+"://"+req.getServerName()+":"+req.getServerPort()+req.getContextPath()+"/";
		String checkCode=req.getParameter("checkCode");
		String sessionCode=(String)req.getSession().getAttribute("code");
		PrintWriter out=resp.getWriter();
		if(checkCode==null || "".equals(checkCode)){
			out.write("");
		}else if(!checkCode.equalsIgnoreCase(sessionCode)){
			out.write("");
		}else{
			out.write("");
		}
		out.flush();
		out.close();
	}
	
	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		// TODO Auto-generated method stub
		this.doGet(req, resp);
	}
}

效果图展示

本文大量参考了 "程序员-形同陌路" 的博客，只做了很少修改，大家可以去看他的博客，更详细。

博客地址：http://blog.csdn.net/lulei9876/article/details/8365500/