servlet输出随机验证码

傷城~ 2022-08-12 01:05 193阅读 0赞

public static final int WIDTH = 120;
    	public static final int HEIGHT = 25;
    
    	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		BufferedImage image = new BufferedImage(WIDTH,HEIGHT,BufferedImage.TYPE_INT_RGB);
    		
    		Graphics g = image.getGraphics();
    		
    		//1、设置背景色
    		setBackGroud(g);
    		
    		//2.设置边框	
    		setBorder(g);
    		
    		//3.画干扰线
    		drawRandomLine(g);
    		
    		//4.写随机数
    		drawRandomNum((Graphics2D)g);
    		
    		//5.图形写给浏览器 
    		response.setContentType("image/jpeg");
    		//发图控制浏览器不要缓存
    		response.setDateHeader("expries", -1);
    		response.setHeader("cache-control", "no-cache");
    		response.setHeader("Pragma", "no-cache");
    		ImageIO.write(image, "jpg", response.getOutputStream());
    	}
    	
    	private void setBackGroud(Graphics g) {
    		g.setColor(Color.WHITE);
    		//填充矩形
    		g.fillRect(0, 0, WIDTH, HEIGHT);
    	}
    
    	private void setBorder(Graphics g) {
    		g.setColor(Color.BLUE);
    		
    		g.drawRect(1, 1, WIDTH-2, HEIGHT-2);
    	}
    	
    	private void drawRandomLine(Graphics g) {
    		g.setColor(Color.GREEN);
    		
    		for(int i=0; i<5; i++){
    			int x1 = new Random().nextInt(WIDTH);
    			int y1 = new Random().nextInt(HEIGHT);
    			int x2 = new Random().nextInt(WIDTH);
    			int y2 = new Random().nextInt(HEIGHT);
    			g.drawLine(x1, y1, x2, y2);
    		}
    	}
    	
    	private void drawRandomNum(Graphics2D g) {
    		g.setColor(Color.RED);
    		g.setFont(new Font("宋体",Font.BOLD,20));
    		
    		//中文字所在区间  [\u4e00-\u9fa5]
    		String base = "ABCDEFGHIJK";
    		int x = 10;
    		for(int i=0; i<4; i++){
    			
    			//设置旋转角度
    			int degree = new Random().nextInt()%30;//生成正负30内数
    			String ch = base.charAt(new Random().nextInt(base.length()))+"";
    			
    			g.rotate(degree*Math.PI/180, x, 20);
    			g.drawString(ch, x, 20);
    			g.rotate(-degree*Math.PI/180, x, 20);//旋转回去
    			x+=30;
    		}
    	}