Servlet简单验证码的实现

Servlet简单验证码的实现

 

1.生成验证码图片：RandomValidateCode.java

 

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.util.Random;

import javax.imageio.ImageIO;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class RandomValidateCode {

    public static final String RANDOMCODEKEY = "RANDOMVALIDATECODEKEY";//放到session中的key
    private Random random = new Random();
    private String randString = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";//随机产生的字符串
    
    private int width = 80;//图片宽
    private int height = 26;//图片高
    private int lineSize = 20;//干扰线数量
    private int stringNum = 4;//随机产生字符数量
    /*
     * 获得字体
     */
    private Font getFont(){
        return new Font("Fixedsys",Font.CENTER_BASELINE,18);
    }
    /*
     * 获得颜色
     */
    private Color getRandColor(int fc,int bc){
        if(fc > 255)
            fc = 255;
        if(bc > 255)
            bc = 255;
        int r = fc + random.nextInt(bc-fc-16);
        int g = fc + random.nextInt(bc-fc-14);
        int b = fc + random.nextInt(bc-fc-18);
        return new Color(r,g,b);
    }
    /**
     * 生成随机图片
     */
    public void getRandcode(HttpServletRequest request,
            HttpServletResponse response) {
        HttpSession session = request.getSession();
        //BufferedImage类是具有缓冲区的Image类,Image类是用于描述图像信息的类
        BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_BGR);
        Graphics g = image.getGraphics();//产生Image对象的Graphics对象,改对象可以在图像上进行各种绘制操作
        g.fillRect(0, 0, width, height);
        g.setFont(new Font("Times New Roman",Font.ROMAN_BASELINE,18));
        g.setColor(getRandColor(110, 133));
        //绘制干扰线
        for(int i=0;i<=lineSize;i++){
            drowLine(g);
        }
        //绘制随机字符
        String randomString = "";
        for(int i=1;i<=stringNum;i++){
            randomString=drowString(g,randomString,i);
        }
        session.removeAttribute(RANDOMCODEKEY);
        session.setAttribute(RANDOMCODEKEY, randomString);
        System.out.println(randomString);
        g.dispose();
        try {
            ImageIO.write(image, "JPEG", response.getOutputStream());//将内存中的图片通过流动形式输出到客户端
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    /*
     * 绘制字符串
     */
    private String drowString(Graphics g,String randomString,int i){
        g.setFont(getFont());
        g.setColor(new Color(random.nextInt(101),random.nextInt(111),random.nextInt(121)));
        String rand = String.valueOf(getRandomString(random.nextInt(randString.length())));
        randomString +=rand;
        g.translate(random.nextInt(3), random.nextInt(3));
        g.drawString(rand, 13*i, 16);
        return randomString;
    }
    /*
     * 绘制干扰线
     */
    private void drowLine(Graphics g){
        int x = random.nextInt(width);
        int y = random.nextInt(height);
        int xl = random.nextInt(13);
        int yl = random.nextInt(15);
        g.drawLine(x, y, x+xl, y+yl);
    }
    /*
     * 获取随机的字符
     */
    public String getRandomString(int num){
        return String.valueOf(randString.charAt(num));
    }
}

 

 

2.把图片传到浏览器上的servlet：ImageServlet.java

 

import java.io.IOException;

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

public class ImageServlet extends HttpServlet {

	/**
	 * Constructor of the object.
	 */
	public ImageServlet() {
		super();
	}

	/**
	 * Destruction of the servlet. <br>
	 */
	public void destroy() {
		super.destroy(); // Just puts "destroy" string in log
		// Put your code here
	}

	/**
	 * The doGet method of the servlet. <br>
	 *
	 * This method is called when a form has its tag value method equals to get.
	 * 
	 * @param request the request send by the client to the server
	 * @param response the response send by the server to the client
	 * @throws ServletException if an error occurred
	 * @throws IOException if an error occurred
	 */
	private static final long serialVersionUID = 1L;
	
	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
        response.setContentType("image/jpeg");//设置相应类型,告诉浏览器输出的内容为图片
        response.setHeader("Pragma", "No-cache");//设置响应头信息，告诉浏览器不要缓存此内容
        response.setHeader("Cache-Control", "no-cache");
        response.setDateHeader("Expire", 0);
        RandomValidateCode randomValidateCode = new RandomValidateCode();
        try {
            randomValidateCode.getRandcode(request, response);//输出图片方法
        } catch (Exception e) {
            e.printStackTrace();
        }
	}

	/**
	 * The doPost method of the servlet. <br>
	 *
	 * This method is called when a form has its tag value method equals to post.
	 * 
	 * @param request the request send by the client to the server
	 * @param response the response send by the server to the client
	 * @throws ServletException if an error occurred
	 * @throws IOException if an error occurred
	 */	
	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		doGet(request, response);
	}

	/**
	 * Initialization of the servlet. <br>
	 *
	 * @throws ServletException if an error occurs
	 */
	public void init() throws ServletException {
		// Put your code here
	}

}

 

3.web.xml添加映射（重要！！！）：

<servlet-mapping >
    <servlet-name>valid</servlet-name>
    <url-pattern>/valid</url-pattern>
</servlet-mapping>

<servlet>
    <servlet-name>valid</servlet-name>
    <servlet-class>com.datanew.czfc.validateCode.ImageServlet</servlet-class>
</servlet>

 

注意匹配方式：

/* 1. 完全匹配 */
  <url-pattern>/test/list.do</url-pattern>  

/* 2. 路径匹配 */
  <url-pattern>/*</url-pattern> //匹配根路径下的全部请求

/* 3. 扩展名匹配 */
  <url-pattern>*.do</url-pattern> //匹配.do结尾的请求
  <url-pattern>*.html</url-pattern> //匹配全部html结尾的请求
  <url-pattern>*</url-pattern> //不能用*，否则报错

 

 

4.jsp显示验证码图片和输入验证码：

<tr>
  <td height="37" align="right"><span class="STYLE1">验证码：</span></td>
  <td><input name="validCode" class="login_valid" maxlength="4"/>&nbsp;<img id="validCode" src="valid" onclick="changeCode()" title="点击更换" /></td>
</tr>

或者：
<img id="validCode" src="valid" onClick="document.getElementById('validCode').src ='valid?rand='+new Date();" title="点击更换"/>

注意：有的地方的<img>标签中的src="/valid"，此处有斜杠“/”，表示的是绝对路径，地址为：127.0.0.1：8080/valid （——8080后面少了项目名！）

 

5.刷新验证码的脚本（重要！）：

/**方式一：测试失败——原因：src无变化！！！*/
/* function changeCode(){
	document.getElementById("validCode").src="valid"; 
} *

/**方式二：测试成功！*/
function changeCode(){
	document.getElementById('validCode').src ='valid?rand='+new Date();
}
/**方式三：Chrome测试成功！Firefox和IE测试失败！！！*/
function changeCode(){  
    var request = getXMLRequest();//得到XMLHttpRequest对象  
    request.onreadystatechange = function(){  
        if(request.readyState == 4){  
            document.getElementById("validCode").src = "valid";//改变验证码图片  
        }  
    }  
                //将请求发送出去  
    request.open("GET","valid",true);  
    request.send(null);  
}  

function getXMLRequest(){  
    var request;  
    try{  
        //for火狐等浏览器  
        request = new XMLHttpRequest();  
    }catch(e){  
        try{  
            //for IE  
            request = new ActiveXObject("Microsoft.XMLHttp");    
        }catch(e){  
            alert("您的浏览器不支持AJAX!!!");  
            return null;  
        }  
    }  
    return request;  
}  

 

6.登录验证：

boolean valid = false;
String validCode = request.getParameter("validCode");
String oldCode = (String) request.getSession().getAttribute("RANDOMVALIDATECODEKEY");
if (validCode !=null && validCode.equalsIgnoreCase(oldCode)) {
	valid = true;
}