生成验证码的几种方式

1，在jsp页面中直接生成验证码

//image.jsp
<%@ page contentType="image/jpeg"
	import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*"
	pageEncoding="GBK"%>
<%!Color getRandColor(int fc, int bc) {//给定范围获得随机颜色
		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);
	}%>
<%
	//设置页面不缓存
	response.setHeader("Pragma", "No-cache");
	response.setHeader("Cache-Control", "no-cache");
	response.setDateHeader("Expires", 0);

	// 在内存中创建图象
	// 通过这里可以修改图片大小
	int width = 85, height = 23;
	BufferedImage image = new BufferedImage(width, height,
			BufferedImage.TYPE_INT_RGB);

	// 获取图形上下文
	// g相当于笔
	Graphics g = image.getGraphics();

	//生成随机类
	Random random = new Random();

	// 设定背景色
	g.setColor(getRandColor(200, 250));
	// 画一个实心的长方，作为北京
	g.fillRect(0, 0, width, height);

	//设定字体
	g.setFont(new Font("黑体", Font.PLAIN, 18));

	//画边框
	g.setColor(Color.BLUE);
	g.drawRect(0,0,width-1,height-1);

	// 随机产生155条干扰线，使图象中的认证码不易被其它程序探测到
	g.setColor(getRandColor(160, 200));
	for (int i = 0; i < 155; i++) {
		int x = random.nextInt(width);
		int y = random.nextInt(height);
		int xl = random.nextInt(12);
		int yl = random.nextInt(12);
		g.drawLine(x, y, x + xl, y + yl);
	}

	// 取随机产生的认证码(4位数字)
	//String rand = request.getParameter("rand");
	//rand = rand.substring(0,rand.indexOf("."));
	String sRand = "";
	// 如果要使用中文，必须定义字库，可以使用数组进行定义
	// 这里直接写中文会出乱码，必须将中文转换为unicode编码
	String[] str = { "A", "B", "C", "D", "E", "F", "G", "H", "J", "K",
			"L", "M", "N", "P", "Q", "R", "S", "T", "U", "V", "W", "X",
			"Y", "Z", "a", "b", "c", "d", "e", "f", "g", "h", "i", "j",
			"k", "m", "n", "p", "s", "t", "u", "v", "w", "x", "y", "z",
			"1", "2", "3", "4", "5", "6", "7", "8", "9" };

	for (int i = 0; i < 5; i++) {
		String rand = str[random.nextInt(str.length)];
		sRand += rand;
		// 将认证码显示到图象中
		g.setColor(new Color(20 + random.nextInt(110), 20 + random
				.nextInt(110), 20 + random.nextInt(110)));//调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成
		g.drawString(rand, 16 * i + 6, 19);
	}

	// 将认证码存入SESSION
	session.setAttribute("rand", sRand);

	// 图象生效
	g.dispose();

	// 输出图象到页面
	ImageIO.write(image, "JPEG", response.getOutputStream());
	out.clear();
	out = pageContext.pushBody();
%>

//使用验证码的页面login.jsp
<%@ page contentType="text/html" pageEncoding="GBK"%>

	
		
		
	
	
		
			<%
				// 乱码解决
				request.setCharacterEncoding("GBK");
			%>
			

				登陆程序
			
			

			<%=request.getAttribute("info") != null ? request
					.getAttribute("info") : ""%>
			

				用户ID：
				
				

				密  码：
				
				

				验证码：
				
				
				

				
				
			
		
	

效果如下：

2，使用Servlet生成验证码

//IdentityServlet.java代码如下：
package com.helloweenvsfei.servlet;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

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

import com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGImageEncoder;

public class IdentityServlet extends HttpServlet {

	/**
	 * 
	 */
	private static final long serialVersionUID = -479885884254942306L;

	public static final char[] CHARS = { '2', '3', '4', '5', '6', '7', '8',
			'9', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'J', 'K', 'L', 'M',
			'N', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z' };

	public static Random random = new Random();

	public static String getRandomString() {
		StringBuffer buffer = new StringBuffer();
		for (int i = 0; i < 6; i++) {
			buffer.append(CHARS[random.nextInt(CHARS.length)]);
		}
		return buffer.toString();
	}

	public static Color getRandomColor() {
		return new Color(random.nextInt(255), random.nextInt(255), random
				.nextInt(255));
	}

	public static Color getReverseColor(Color c) {
		return new Color(255 - c.getRed(), 255 - c.getGreen(), 255 - c
				.getBlue());
	}

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		response.setContentType("image/jpeg");

		String randomString = getRandomString();
		request.getSession(true).setAttribute("randomString", randomString);

		int width = 100;
		int height = 30;

		Color color = getRandomColor();
		Color reverse = getReverseColor(color);

		BufferedImage bi = new BufferedImage(width, height,
				BufferedImage.TYPE_INT_RGB);
		Graphics2D g = bi.createGraphics();
		g.setFont(new Font(Font.SANS_SERIF, Font.BOLD, 16));
		g.setColor(color);
		g.fillRect(0, 0, width, height);
		g.setColor(reverse);
		g.drawString(randomString, 18, 20);
		for (int i = 0, n = random.nextInt(100); i < n; i++) {
			g.drawRect(random.nextInt(width), random.nextInt(height), 1, 1);
		}

		// 转成JPEG格式
		ServletOutputStream out = response.getOutputStream();
		JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);
		encoder.encode(bi);
		out.flush();
	}

	public static void main(String[] args) {
		System.out.println(getRandomString());
	}
}

//Web.xml的配置为：

    IdentityServlet
    com.helloweenvsfei.servlet.IdentityServlet


    IdentityServlet
    /servlet/IdentityServlet

//测试页面identity.html为：


	
		

		
		
		

		

	

	



		
		

	

3，在Struts2应用中生成验证码

//RandomNumUtil.java
package org.ml.util;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.util.Random;
import javax.imageio.ImageIO;
import javax.imageio.stream.ImageOutputStream;

public class RandomNumUtil {
	public static final char[] CHARS = {'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'J', 'K', 'L', 'M',
		'N', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z','2', '3', '4', '5', '6', '7', '8',
		'9','a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'm',
		'n', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z'}; 
	private ByteArrayInputStream image;// 图像
	private String str;// 验证码
	/**
	 *  构造方法调用初始化属性方法
	 */
	private RandomNumUtil() {
		init();
	}

	/**
	 * 取得RandomNumUtil实例
	 */
	public static RandomNumUtil Instance() {
		return new RandomNumUtil();
	}

	/**
	 * 取得验证码图片
	 */
	public ByteArrayInputStream getImage() {
		return this.image;
	}

	/**
	 * 取得图片的验证码
	 */
	public String getString() {
		return this.str;
	}
	
	/**
	 * 初始化属性否具体方法
	 */
	private void init() {
		// 在内存中创建图象
		int width = 85, height = 18;
		//设置图形的高度和宽度，以及RGB类型
		BufferedImage image = new BufferedImage(width, height,
				BufferedImage.TYPE_INT_RGB);
		// 获取图形上下文
		Graphics g = image.getGraphics();
		// 生成随机类
		Random random = new Random();
		// 设定背景色
		g.setColor(getRandColor(200, 250));
		g.fillRect(0, 0, width, height);
		// 设定字体
		g.setFont(new Font("Times New Roman", Font.PLAIN, 18));
		// 随机产生255条干扰线，使图象中的认证码不易被其它程序探测到
		g.setColor(getRandColor(160, 200));
		for (int i = 0; i < 255; i++) {
			int x = random.nextInt(width);
			int y = random.nextInt(height);
			int xl = random.nextInt(12);
			int yl = random.nextInt(12);
			g.drawLine(x, y, x + xl, y + yl);
		}
		// 取随机产生的认证码(6位数字)
		StringBuffer sRand = new StringBuffer();  
		for (int i = 0; i < 6; i++) {
			String rand = String.valueOf(CHARS[random.nextInt(CHARS.length-1)]);//从字符数组中随机产生一个字符
			sRand.append(rand); 
			// 将认证码显示到图象中
			g.setColor(new Color(20 + random.nextInt(110), 20 + random.nextInt(110), 20 + random.nextInt(110)));
			// 调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成
			g.drawString(rand, 13 * i + 6, 17);
		}
		// 赋值验证码
		this.str = sRand.toString();

		// 图象生效
		g.dispose();
		//下面将生成的图形转变为图片
		ByteArrayOutputStream output = new ByteArrayOutputStream(); 
		ByteArrayInputStream input = null;
		try {
			ImageOutputStream imageOut = ImageIO.createImageOutputStream(output);
			ImageIO.write(image, "JPEG", imageOut);//将图像按JPEG格式写入到imageOut中，即存入到output的字节流中
			imageOut.close();//关闭写入流
			input = new ByteArrayInputStream(output.toByteArray());//input读取output中的图像信息
		} catch (Exception e) {
			System.out.println("验证码图片产生出现错误：" + e.toString());
		}

		this.image = input;/* 赋值图像 */
	} 
	/*
	 * 给定范围获得随机颜色
	 */
	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);
	}
}

//RandomAction.java的代码：
package org.ml.action;

import java.io.ByteArrayInputStream;

import org.ml.util.RandomNumUtil;

import com.opensymphony.xwork2.ActionContext;
import com.opensymphony.xwork2.ActionSupport;

@SuppressWarnings("serial")
public class RandomAction extends ActionSupport {
	private ByteArrayInputStream inputStream;

	public String execute() throws Exception {
		RandomNumUtil rdnu = RandomNumUtil.Instance();//取得随机验证码产生类的对象
		this.setInputStream(rdnu.getImage());// 取得带有随机字符串的图片
		ActionContext.getContext().getSession().put("random", rdnu.getString());// 取得随机字符串放入HttpSession
		return SUCCESS;
	}

	public void setInputStream(ByteArrayInputStream inputStream) {
		this.inputStream = inputStream;
	}

	public ByteArrayInputStream getInputStream() {
		return inputStream;
	}
}

//struts.xml配置为：


    
	image/JPEG
	inputStream
    

//HTML中的表单代码为：

 
   验证码：