jsp之简单的验证码生成

<%@page import="java.awt.image.ImageObserver"%>
<%@page import="java.awt.Image"%>
<%@page import="java.awt.Toolkit"%>
<%@page import="java.awt.Font"%>
<%@page import="java.util.Random"%>
<%@page import="javax.imageio.ImageIO"%>
<%@page import="java.awt.Color"%>
<%@page import="java.awt.Graphics"%>
<%@page import="java.awt.image.BufferedImage"%>
<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%!private Random rnd = new Random();%>

<%
    //设置图片格式
    response.setContentType("image/png");
    //内存图片
    BufferedImage bi = new BufferedImage(200, 200, BufferedImage.TYPE_INT_RGB);

    //获取画笔
    Graphics g = bi.getGraphics();

    //绘制图片
    //获取工程所在的根目录
    String fileName = application.getRealPath("xx.png");
    System.out.println(fileName);
    Image img = Toolkit.getDefaultToolkit().getImage(fileName);
    g.drawImage(img, 0, 0, 200, 200, null);

    //绘图图案
    g.setColor(Color.WHITE);//将画笔设置成白色
    //g.fillRect(0, 0, 200, 200);//画填充矩形
    g.setColor(Color.BLACK);
    g.drawRect(1, 1, 198, 198);//画轮廓矩形
    //干扰线
    int lines = 100;
    g.setColor(Color.GRAY);
    for (int i = 0; i < lines; i++) {
        int x1 = rnd.nextInt(201);
        int x2 = rnd.nextInt(201);
        int y1 = rnd.nextInt(201);
        int y2 = rnd.nextInt(201);

        g.drawLine(x1, y1, x2, y2);
    }
    //生成随机数
    String x = "";
    for (int i = 0; i < 6; i++) {
        x += rnd.nextInt(10);
    }
    System.out.print(x);
    g.setColor(Color.RED);
    g.setFont(new Font("黑体", Font.PLAIN, 40));
    g.drawString(x, 30, 100);//画文字
    //将图片输出到浏览器
    ImageIO.write(bi, "png", response.getOutputStream());
    //释放资源
    g.dispose();

    out.clear();
    out = pageContext.pushBody();
%>

点击图片刷新验证码

    <img width="100px" alt="验证码" src="img.jsp" onclick="this.src='img.jsp?ran='+Math.random();">