java生成验证码

1. 本质：图片

2. 目的：防止恶意表单注册

3.代码：

package cn.itcast.web.servlet;

import javax.imageio.imageio;
import javax.servlet.servletexception;
import javax.servlet.servletoutputstream;
import javax.servlet.annotation.webservlet;
import javax.servlet.http.httpservlet;
import javax.servlet.http.httpservletrequest;
import javax.servlet.http.httpservletresponse;
import java.awt.*;
import java.awt.image.bufferedimage;
import java.io.ioexception;
import java.util.random;

@webservlet("/checkcodeservlet")
public class checkcodeservlet extends httpservlet {
    protected void dopost(httpservletrequest request, httpservletresponse response) throws servletexception, ioexception {


        int width = 100;
        int height = 50;

        //1.创建一对象，在内存中图片(验证码图片对象)
        bufferedimage image = new bufferedimage(width,height,bufferedimage.type_int_rgb);


        //2.美化图片
        //2.1 填充背景色
        graphics g = image.getgraphics();//画笔对象
        g.setcolor(color.pink);//设置画笔颜色
        g.fillrect(0,0,width,height);

        //2.2画边框
        g.setcolor(color.blue);
        g.drawrect(0,0,width - 1,height - 1);

        string str = "abcdefghijklmnopqrstuvwxyzabcdefghigklmnopqrstuvwxyz0123456789";
        //生成随机角标
        random ran = new random();

        for (int i = 1; i <= 4; i++) {
            int index = ran.nextint(str.length());
            //获取字符
            char ch = str.charat(index);//随机字符
            //2.3写验证码
            g.drawstring(ch+"",width/5*i,height/2);
        }


        //2.4画干扰线
        g.setcolor(color.green);

        //随机生成坐标点

        for (int i = 0; i < 10; i++) {
            int x1 = ran.nextint(width);
            int x2 = ran.nextint(width);

            int y1 = ran.nextint(height);
            int y2 = ran.nextint(height);
            g.drawline(x1,y1,x2,y2);
        }


        //3.将图片输出到页面展示
        imageio.write(image,"jpg",response.getoutputstream());


    }

    protected void doget(httpservletrequest request, httpservletresponse response) throws servletexception, ioexception {
        this.dopost(request,response);
    }
}