- _nosay
Servlet生成图片验证码
2017-11-19 11:36:02
背景知识:
用户在注册或者登陆的过程中,经常会遇到必须输入验证码的情况,那这个验证码主要是为了防止恶意程序访问服务器而设置的。
实现原理:
浏览器显示文档和图片,是由服务器回送给浏览器的响应完成的,而一个响应要封装成一个HttpServletResponse对象,所以我们只需要将验证码的图片封装到HttpServletResponse对象返回给浏览器即可。
相关代码
package net.zixue.servlet; import javax.imageio.ImageIO; import javax.servlet.ServletException; 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(name = "Test3Servlet",urlPatterns = "/test3") public class Test3Servlet extends HttpServlet { protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { int width = 100; int height = 30; String data = "abcdefghijklmnopqrstuvwxyz0123456789"; Random random = new Random(); BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_BGR); Graphics graphics = image.getGraphics(); graphics.setColor(Color.gray); graphics.fillRect(0,0,width,height); graphics.setColor(Color.black); for(int i=0;i<4;i++) { int position = random.nextInt(data.length()); String substring = data.substring(position, position + 1); graphics.drawString(substring,width/5*(i+1),15); } ImageIO.write(image,"jpg",response.getOutputStream()); } }