jsp实现验证码

//1、验证码界面
	//验证码的宽和高
	int width = 70;
	int height = 30;
	/*
	*图像缓冲对象（注意：在多次对某个对象操作时，为了提高效率，很多时候选择用缓冲对象来进行操作，
	因为缓冲类的对象很多时候是可以即时改变对象的数据的）
	*/
	BufferedImage bufferedImage = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
	//创建图像操作对象，用于操作验证码图片对象
	Graphics2D g = bufferedImage.createGraphics();
	//创建字体对象方便操作图像字体的属性
	Font font = new Font("Times New Roman",Font.PLAIN,18);
	g.setFont(font);
	//设置相关颜色等等
	g.setColor(Color.BLACK);
	g.drawRect(0,0,width-1,height-1);
	g.setColor(Color.GRAY);

//2、产生随机数
	//定义生成随机数的对象
	Random random = new Random();
	//产生干扰线
	for(int i=0;i<40;i++){
		//设置40条干扰线
		int x1 = random.nextInt(width);
		int y1 = random.nextInt(height);
		int x2 = random.nextInt(10);
		int y2 = random.nextInt(10);
		//将随机线条描绘到验证码对象中
		g.drawLine(x1,y1,x1+x2,y1+y2);
	}
	//产生随机数
	//定义随机数的个数
	int length = 4
	//定义 变量存储随机数字变量
	BufferedString str_random = new BufferedString();//定义成缓冲字符类型是为了提高效率
	for(int i=0;i<length;i++){
		int num_random = random.nextInt(10);
		String str_num = String.valueOf(num_random);
		g.drawString(str_num);
		str_random.append(str_num);
	}

//3、发送验证码图片数据
	bufferedImg.flush();//刷新与图像缓冲有关的数据
	g.dispose();//释放与Graphice2D有关的对象的资源
	String randomCode = str_random.toString();
	session.setAttribute("randomCode",randomCode.toString());//通过session传递随机码给其他页面用于验证身份
	ServletOutputStream outputStream = response.getOutputStream();
	ImageIO.write(bufferedImg,"jpeg",outputStream);
	
	outputStream.close();
	
	out.clear();
	out=pageContext.pushBody();

int width = 70,height = 22;
	if(request.getParameter("width")!=null){
		try{
			width=Integer.parseInt(request.getParameter("width"));
		}catch(NumberFormatException e) {
			
		}
	}
	BufferedImage bufferedImg = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
	Graphics2D g = bufferedImg.createGraphics();
	
	g.setColor(Color.WHITE);
	g.fillRect(0,0,width,height);
	
	Font font = new Font("Times New Roman",Font.PLAIN,18);
	g.setFont(font);
	
	g.setColor(Color.BLACK);
	g.drawRect(0,0,width-1,height-1);
	g.setColor(Color.GRAY);
	
	Random random = new Random();//设置随机种子
	
	for(int i=0;i<40;i++){
		//设置40条干扰线
		int x1 = random.nextInt(width);
		int y1 = random.nextInt(height);
		int x2 = random.nextInt(10);
		int y2 = random.nextInt(10);
		g.drawLine(x1,y1,x1+x2,y1+y2);
	}
	
	int length = 4;//设置默认生成四个长度的验证码
	if(request.getParameter("length")!=null){
		try{
			length = Integer.parseInt(request.getParameter("length"));
		}catch(NumberFormatException e){
			out.println("<script>alert(‘无法加载验证码，请重新操作！‘)</script");
			e.printStackTrace();
		}
	}
	//定义变量存储运算结果
	int result = 0;
	//定义一个int用于存储某个数字后面的运算符，1代表+，2代表-，初始化为0
	int int_sign = 0;
	for(int i = 0;i<length;i++){//获取随机数字字符串
		int num_random = random.nextInt(10);
		//根据符号标记标量int_sign进行相应的运算
		if(int_sign==2){
			result = result - num_random;
		}else{
			result = result + num_random;
		}
		String strRand = String.valueOf(num_random);
		g.setColor(Color.RED);
		g.drawString(strRand,13 * i + 6, 16);
		//随机获取运算符号
		if(i<length-1){
			int sign_random = random.nextInt(2);
			if(sign_random<1){
				g.setColor(Color.GREEN);
				g.drawString("+",13 * i + 12, 16);
				int_sign = 1;
			}else{
				g.setColor(Color.BLUE);
				g.drawString("-",13 * i + 12, 16);
				int_sign = 2;
			}
		}else{
			g.drawString("=?",13 * i + 12, 16);
		}
		
	}
	bufferedImg.flush();
	g.dispose();
	
	session.setAttribute("randomCode",result);
	
	response.setContentType("image/jpeg");
	response.setHeader("Pragam","no-cache");
	response.setHeader("Cache-Control","no-cache");
	response.setDateHeader("Expires",0);
	
	ServletOutputStream outputStream = response.getOutputStream();
	ImageIO.write(bufferedImg,"jpeg",outputStream);
	
	outputStream.close();
	
	out.clear();
	out=pageContext.pushBody();