JSP + Servlet实现生成登录验证码示例

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随机生成四位数验证码，包括汉字，数字，英文大小写。
1.Servlet类

package servlet;
import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.geom.AffineTransform;
import java.awt.geom.Line2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.PrintWriter;
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;
import javax.servlet.http.HttpSession;
public class PictureCheckCode extends HttpServlet {
   private static final long serialVersionUID = 1L; 
  public PictureCheckCode() { 
    super(); 
  } 
  public void destroy() { 
    super.destroy();  
  } 
  public void init() throws ServletException { 
    super.init(); 
  } 
  /*该方法主要作用是获得随机生成的颜色*/  
  public Color getRandColor(int s,int e){ 
    Random random=new Random (); 
    if(s>255) s=255; 
    if(e>255) e=255; 
    int r,g,b; 
    r=s+random.nextInt(e-s);  //随机生成RGB颜色中的r值 
    g=s+random.nextInt(e-s);  //随机生成RGB颜色中的g值 
    b=s+random.nextInt(e-s);  //随机生成RGB颜色中的b值 
    return new Color(r,g,b); 
  } 
  public void doGet(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
  System.out.println("this is doGet method");
  this.doPost(request, response);
  }
  public void doPost(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
  //设置不缓存图片 
  response.setHeader("Pragma", "No-cache"); 
  response.setHeader("Cache-Control", "No-cache"); 
  response.setDateHeader("Expires", 0); 
  //指定生成的响应图片,一定不能缺少这句话,否则错误. 
  response.setContentType("image/jpeg"); 
  int width=80,height=35;   //指定生成验证码的宽度和高度 
  BufferedImage image=new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB); //创建BufferedImage对象,其作用相当于一图片 
  Graphics g=image.getGraphics();   //创建Graphics对象,其作用相当于画笔 
  Graphics2D g2d=(Graphics2D)g;  //创建Grapchics2D对象 
  Random random=new Random(); 
  Font mfont=new Font("楷体",Font.BOLD,16); //定义字体样式 
  g.setColor(getRandColor(200,250)); 
  g.fillRect(0, 0, width, height);  //绘制背景 
  g.setFont(mfont);      //设置字体 
  g.setColor(getRandColor(180,200)); 
  //绘制100条颜色和位置全部为随机产生的线条,该线条为2f 
  for(int i=0;i<100;i++){ 
    int x=random.nextInt(width-1); 
    int y=random.nextInt(height-1); 
    int x1=random.nextInt(6)+1; 
    int y1=random.nextInt(12)+1; 
    BasicStroke bs=new BasicStroke(2f,BasicStroke.CAP_BUTT,BasicStroke.JOIN_BEVEL); //定制线条样式 
    Line2D line=new Line2D.Double(x,y,x+x1,y+y1); 
    g2d.setStroke(bs); 
    g2d.draw(line);   //绘制直线 
  } 
  //输出由英文，数字，和中文随机组成的验证文字，具体的组合方式根据生成随机数确定。 
  String sRand=""; 
  String ctmp=""; 
  int itmp=0; 
  //制定输出的验证码为四位 
  for(int i=0;i<4;i++){ 
    switch(random.nextInt(3)){ 
    case 1:   //生成A-Z的字母 
       itmp=random.nextInt(26)+65; 
       ctmp=String.valueOf((char)itmp); 
       break; 
    case 2:   //生成汉字 
       String[] rBase={"0","1","2","3","4","5","6","7","8","9","a","b","c","d","e","f"};  
       //生成第一位区码 
       int r1=random.nextInt(3)+11; 
       String str_r1=rBase[r1]; 
       //生成第二位区码 
       int r2; 
       if(r1==13){ 
       r2=random.nextInt(7);   
       }else{ 
       r2=random.nextInt(16); 
       } 
       String str_r2=rBase[r2]; 
       //生成第一位位码 
       int r3=random.nextInt(6)+10; 
       String str_r3=rBase[r3]; 
       //生成第二位位码 
       int r4; 
       if(r3==10){ 
       r4=random.nextInt(15)+1; 
       }else if(r3==15){ 
       r4=random.nextInt(15); 
       }else{ 
       r4=random.nextInt(16); 
       } 
       String str_r4=rBase[r4]; 
       //将生成的机内码转换为汉字 
       byte[] bytes=new byte[2]; 
       //将生成的区码保存到字节数组的第一个元素中 
       String str_12=str_r1+str_r2; 
       int tempLow=Integer.parseInt(str_12, 16); 
       bytes[0]=(byte) tempLow; 
       //将生成的位码保存到字节数组的第二个元素中 
       String str_34=str_r3+str_r4; 
       int tempHigh=Integer.parseInt(str_34, 16); 
       bytes[1]=(byte)tempHigh; 
       ctmp=new String(bytes); 
       break; 
    default: 
       itmp=random.nextInt(10)+48; 
       ctmp=String.valueOf((char)itmp); 
       break; 
    } 
    sRand+=ctmp; 
    Color color=new Color(20+random.nextInt(110),20+random.nextInt(110),random.nextInt(110)); 
    g.setColor(color); 
    //将生成的随机数进行随机缩放并旋转制定角度 PS.建议不要对文字进行缩放与旋转,因为这样图片可能不正常显示 
    /*将文字旋转制定角度*/ 
    Graphics2D g2d_word=(Graphics2D)g; 
    AffineTransform trans=new AffineTransform(); 
    trans.rotate((45)*3.14/180,15*i+8,7); 
    /*缩放文字*/ 
    float scaleSize=random.nextFloat()+0.8f; 
    if(scaleSize>1f) scaleSize=1f; 
    trans.scale(scaleSize, scaleSize); 
    g2d_word.setTransform(trans); 
    g.drawString(ctmp, 15*i+18, 14); 
  } 
  HttpSession session=request.getSession(true); 
  session.setAttribute("randCheckCode", sRand); 
  System.out.println(sRand);
  g.dispose();  //释放g所占用的系统资源 
  ImageIO.write(image,"JPEG",response.getOutputStream()); //输出图片 
  }
}

2.web.xml配置

<servlet>
  <description>This is the description of my J2EE component</description>
  <display-name>This is the display name of my J2EE component</display-name>
  <servlet-name>PictureCheckCode</servlet-name>
  <servlet-class>servlet.PictureCheckCode</servlet-class>
 </servlet>
<servlet-mapping>
  <servlet-name>PictureCheckCode</servlet-name>
  <url-pattern>/pictureCheckCode</url-pattern>
 </servlet-mapping>

3.jsp页面输出验证码

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>登录页面</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<script language="javascript">
  function myReload() {
  document.getElementById("CreateCheckCode").src = document
    .getElementById("CreateCheckCode").src
    + "?nocache=" + new Date().getTime();
  }
</script>
</head>
<body>
  <form action="loginServlet" method="get">
    <p class="font tdheight">
    验证码：<input type="text" name="checkCode"
      style="width:70px;height:35px;"> <img
      src="pictureCheckCode" id="CreateCheckCode" align="middle"
      style="margin-top:-10px;"> <br> <a href=""
      
      style="font-size:12px;color:red;margin-left:156px;"> 看不清,换一个</a>
    </p>
    <br><input type="submit" value="提交"
      class="font" style="width:240px;height:35px;background:#f19e28">
  </form>
</body>
</html>

4.后台Servlet判断验证码是否与输入一致

通过request.getParameter(“checkCode”)获取输入验证码，与session.getAttribute(“randCheckCode”)比较是否一致。

public void doGet(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
  String code = request.getParameter("checkCode");
  HttpSession session = request.getSession();
  if (!code.equals(session.getAttribute("randCheckCode"))) {
    request.setAttribute("errormsg", "验证码不正确");
  } 
  System.out.println(request.getAttribute("errormsg"));
  }

运行结果：

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持CodeAE代码之家。

[JSP] JSP + Servlet实现生成登录验证码示例

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