java实现点击图片文字验证码

效果图如上，

package cn.gdin.captcha;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.UnsupportedEncodingException;
import java.util.Random;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class JcaptchaServlet extends HttpServlet {
   Random random = new Random();
   public void doGet(HttpServletRequest request, HttpServletResponse response)
           throws ServletException, IOException {

       int height = 220; //图片高
       int width = 220; //图片宽
       BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
       Graphics2D g = (Graphics2D) image.getGraphics();
       String picPath= JcaptchaServlet.class.getClassLoader().getResource("../image/"+(random.nextInt(4)+1)+".jpg").getPath(); 读取本地图片，做背景图片


       g.drawImage(ImageIO.read(new File(picPath)), 0, 20, width, height, null); //将背景图片从高度20开始


       g.setColor(Color.white); //设置颜色
       g.drawRect(0, 0, width-1, height-1); //画边框

       g.setFont(new Font("宋体",Font.BOLD,20)); //设置字体
       Integer x=null,y=null; //用于记录坐标
       String target=null; // 用于记录文字
       for(int i=0;i<4;i++){ //随机产生4个文字，坐标，颜色都不同
           g.setColor(new Color(random.nextInt(50)+200, random.nextInt(150)+100, random.nextInt(50)+200));
           String str=getRandomChineseChar();
           int a=random.nextInt(width-100)+50;
           int b=random.nextInt(height-70)+55;
           if(x==null){
               x=a; //记录第一个x坐标
           }
           if(y==null){
               y=b;//记录第一个y坐标
           }
           if(target==null){
               target=str; //记录第一个文字
           }
           g.drawString(str, a, b);
       }
       g.setColor(Color.white);
       g.drawString("点击"+target, 0,20);//写入验证码第一行文字 “点击..”
       request.getSession().setAttribute("gap",x+":"+y);//将坐标放入session
       //5.释放资源
       g.dispose();
       //6.利用ImageIO进行输出
       ImageIO.write(image, "jpg", response.getOutputStream()); //将图片输出

   }
    //网上找的，随机产生汉字的方法
   public String getRandomChineseChar()
    {
              String str = null;
              int hs, ls;
              Random random = new Random();
              hs = (176 + Math.abs(random.nextInt(39)));
              ls = (161 + Math.abs(random.nextInt(93)));
              byte[] b = new byte[2];
              b[0] = (new Integer(hs).byteValue());
              b[1] = (new Integer(ls).byteValue());
              try
              {
                  str = new String(b, "GBk"); //转成中文
              }
              catch (UnsupportedEncodingException ex)
              {
                  ex.printStackTrace();
              }
              return str;
    }
   public void doPost(HttpServletRequest request, HttpServletResponse response)
           throws ServletException, IOException {
       doGet(request, response);
   }

}

前端代码

服务端

package cn.gdin.captcha;

import java.io.IOException;
import java.util.Enumeration;
import java.util.Map;
import java.util.Map.Entry;

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 javax.servlet.http.HttpSession;

/**
* Servlet implementation class Login
*/
@WebServlet("/Login")
public class Login extends HttpServlet {
   private static final long serialVersionUID = 1L;


   protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
       // TODO Auto-generated method stub
       response.setContentType("text/html;charset=utf-8"); //设置编码
        //获取前端传来的坐标

        String xs=request.getParameter("x");
       String ys=request.getParameter("y");
       HttpSession session = request.getSession();

        String str = (String) session.getAttribute("gap");//获取session中的gap
       if(str==null){
           response.getWriter().write("验证码超时");
           return;
       }
       String[] split2 = str.split(":");
       int x=   Integer.parseInt(xs);
       int y=Integer.parseInt(ys);
       int x1=   Integer.parseInt(split2[0]);
       int y1=Integer.parseInt(split2[1]);
       if(x1-2<x && x<x1+22 && y1-22<y && y<y1+2){ //若前端上传的坐标在session中记录的坐标的一定范围内则验证成功
           response.getWriter().write("验证成功");
       }else{
           response.getWriter().write("验证失败");
       }
   }

   /**
   * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
   */
   protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
       // TODO Auto-generated method stub
       doGet(request, response);
   }

}

java实现点击图片文字验证码

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