简单的图形验证码

我用例子解释吧：

先来一个在Servlet中编写验证码的例子：

package com.servlet.checkImage;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Random;

import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGImageEncoder;

public class checkImageDemo extends HttpServlet {
    public static final char[] CHARS={'2','3','4','5','6','7','8','9','A','B','C','D','E','F','G','H','J','K','L','M','N','P','Q','R','S','T','U','V','W','X','Y','Z'};
    public static Random random=new Random();
    
    public static String getRandomString(){
        StringBuffer buffer=new StringBuffer();
        for(int i=0;i<6;i++){
            buffer.append(CHARS[random.nextInt(CHARS.length)]);
        }
        return buffer.toString();
    }

    public static Color getRandomColor(){
        return new Color(random.nextInt(255),random.nextInt(255),random.nextInt(255));
    }
    
    public static Color getReverseColor(Color c){//返回某颜色的反色
        return new Color(255-c.getRed(),255-c.getGreen(),255-c.getBlue());
    }
    
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        request.setCharacterEncoding("UTF-8");
        response.setCharacterEncoding("UTF-8");
        response.setContentType("image/jpeg");//设置输出类型，必须的
        
        String randomString=getRandomString();
        request.getSession(true).setAttribute("randomString", randomString);
        
        int width=100;
        int height=30;
        
        Color color=getRandomColor();//用于背景颜色
        Color reverse=getReverseColor(color);//用于前景颜色
        
        BufferedImage bi=new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);//创建一个彩色图片
        Graphics2D g=bi.createGraphics();//获取绘图对象
        g.setFont(new Font(Font.SANS_SERIF,Font.BOLD,16));//设置字体
        g.setColor(color);
        g.fillRect(0, 0, width, height);//绘制背景
        g.setColor(reverse);
        g.drawString(randomString, 18, 20);
        for(int i=0,n=random.nextInt(100);i<n;i++){
            //最多画100个噪音点
            g.drawRect(random.nextInt(width),random.nextInt(height), 1, 1);//随机噪音点
        }
        ServletOutputStream out=response.getOutputStream();//转化为JPEG格式
        JPEGImageEncoder encoder=JPEGCodec.createJPEGEncoder(out);//编码器
        encoder.encode(bi);//对图片进行编码
        out.flush();//输出到客户端
        
    }

    
    public void doPost(HttpServletRequest request, HttpServletResponse response){
    
    }

    
}

再来一个在类中编写验证码的例子：

package com.servlet.checkImage;

import java.awt.Color;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Random;

import javax.imageio.ImageIO;

public class Image1 {
    public Random random=new Random();
    
    public String[] getRandomString(){
        String validateCode[]=new String[4];
        for(int i=0;i<4;i++){
            validateCode[i]=random.nextInt(10)+"";
        }        
        return validateCode;
    }
    
    public Color getRandomColor(){
        Color color=new Color(random.nextInt(255),random.nextInt(255),random.nextInt(255));
        return color;
    }
    
    public Color getResverseColor(Color color){
        Color reverse=new Color(255-color.getRed(),255-color.getGreen(),255-color.getBlue());//获取该颜色的反色，如果需要噪点或者切割线可以使用这个
        return reverse;
    }
    
    public String getImage(OutputStream os){
        int width=80;
        int height=25;
        
        BufferedImage bi=new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
        Graphics g=bi.getGraphics();//获得一个画笔
        //g.setFont(new Font(Font.SANS_SERIF,Font.BOLD,16));//设置字体
        
        //边框
        g.setColor(Color.black);
        g.drawRect(0, 0, width-1, height-1);
        
        Color back=getRandomColor();
        g.setColor(back);
        g.fillRect(0, 0, width, height);//填充背景
                    
        String[] code=getRandomString();
        for(int i=0;i<code.length;i++){
            g.setColor(getRandomColor());
            g.drawString(code[i], 5+(i+1)*15, 15);
        }
        
        Color reserse=getResverseColor(back);
        g.setColor(reserse);
        g.drawLine(0, random.nextInt(height), width, random.nextInt(height));//干扰线
        g.drawLine(random.nextInt(width), 0,height, random.nextInt(width));

        g.dispose();//释放图文上下文
        
        try {
            ImageIO.write(bi, "JPEG", os);
        } catch (IOException e) {
            e.printStackTrace();
            return "";
        }
        
        return new String(code.toString());
        
    }

}

在类中编写的验证码调用需要一个jsp作为中间介质：

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<%@page contentType="image/jpeg" %>


<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">
    
    <title>My JSP 'tempImage.jsp' starting page</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">
    <!--
    <link rel="stylesheet" type="text/css" href="styles.css">
    -->

  </head>
  
  <body>
     <jsp:useBean id="image" scope="page" class="com.servlet.checkImage.Image1"></jsp:useBean>
     <%
        String str=image.getImage(response.getOutputStream());
        session.setAttribute("checkCode",str);
        
        out.clear();
        out=pageContext.pushBody();
     %>
    
  </body>
</html>

在Servlet中的验证码可以直接调用：

两个的调用示例在这个例子里面：

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">
    
    <title>My JSP 'checkImg.jsp' starting page</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">
    <!--
    <link rel="stylesheet" type="text/css" href="styles.css">
    -->

  </head>
  
  <body>
    <script>
      function reloadImage(m){
      if(m==0){
        document.getElementById('btn').disabled=true;
        document.getElementById('identity').src='checkImageDemo?ts='+new Date().getTime();
      }
      if(m==1){
        document.getElementById('btn1').disabled=true;
        document.getElementById('identity1').src='tempImage.jsp?ts='+new Date().getTime();
      }
      }
      
    </script>
    <img src="checkImageDemo" id="identity" onload="btn.disabled=false;" />
    <input type="button" value="换个图片" onclick="reloadImage(0)" id="btn"/>
    <br/>
    <img src="tempImage.jsp" id="identity1" onload="btn1.disabled=false;" />
    <input type="button" value="换个图片" onclick="reloadImage(1)" id="btn1"/>
  </body>
</html>

至于一些配置的就不啰嗦了。认真看看代码就基本验证码该会制作了。