jsp生成验证码

login_image.jsp

<%@ page contentType="image/jpeg" import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*" pageEncoding="utf-8"%>
<%!
//随机获取图片颜色
Color getRandColor(int fc,int bc){
        Random random = new Random();
        if(fc>255) fc=255;
        if(bc>255) bc=255;
        int r=fc+random.nextInt(bc-fc);
        int g=fc+random.nextInt(bc-fc);
        int b=fc+random.nextInt(bc-fc);
        return new Color(r,g,b);
        }
%>
<%
//response设置
response.setHeader("Pragma","No-cache");
response.setHeader("Cache-Control","no-cache");
response.setDateHeader("Expires", 0);

//设置图片大小
int width=60, height=20;
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

//Graphics图片对象
Graphics g = image.getGraphics();


Random random = new Random();

g.setColor(getRandColor(200,250));
g.fillRect(0, 0, width, height);

g.setFont(new Font("Times New Roman",Font.PLAIN,18));




// 设置图片中的随机数
g.setColor(getRandColor(160,200));
for (int i=0;i<155;i++)
{
	int x = random.nextInt(width);
	int y = random.nextInt(height);
        int xl = random.nextInt(12);
        int yl = random.nextInt(12);
	g.drawLine(x,y,x+xl,y+yl);
}


String sRand="";
for (int i=0;i<4;i++){
    String rand=String.valueOf(random.nextInt(10));
    sRand+=rand;
    g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));//µ÷Óú¯Êý³öÀ´µÄÑÕÉ«Ïàͬ£¬¿ÉÄÜÊÇÒòΪÖÖ×ÓÌ«½Ó½ü£¬ËùÒÔÖ»ÄÜÖ±½ÓÉú³É
    g.drawString(rand,13*i+6,16);
}

// 把随值数放入SESSION
session.setAttribute("VALIDATION_CODE",sRand);

g.dispose();

ImageIO.write(image, "JPEG", response.getOutputStream());
out.clear();
out = pageContext.pushBody();
%> 

loginform.jsp

验证码:
    <input type="text" name="j_validation_code" id="j_validation_code"
      style="font-size: 9pt; background-color: #EDEDED;
      border: 1 inset #BEBEBE" 
      size="17" onfocus="this.style.backgroundColor='#FFF7DA'" 
      tabindex="3" 
      onblur="this.style.backgroundColor='#EDEDED'"> 
    <img src="<c:url value="/common/loginimage.jsp"/>"
      onclick="refurbish()" alt="点击图片显示新的验证码"
      style="margin-top: 10px">

ValidationCodeFilter.java

import javax.servlet.http.HttpServletRequest;

import org.acegisecurity.Authentication;
import org.acegisecurity.AuthenticationException;
import org.acegisecurity.ui.webapp.AuthenticationProcessingFilter;

import com.uiiang.iknow.common.exception.ValidationCodeException;

public class ValidationCodeFilter 
  extends AuthenticationProcessingFilter {
	public Authentication attemptAuthentication(
			HttpServletRequest httpServletRequest)
			throws AuthenticationException {
		String inputValidationCode = httpServletRequest
				.getParameter("j_validation_code");
		// 从Session中取出验证码
		String ssnValidationCode = (String)
                  httpServletRequest.getSession()
                    .getAttribute("VALIDATION_CODE");
		// 取出后就失效，        
               httpServletRequest.getSession()
                  .setAttribute("VALIDATION_CODE",
		  "Game Over");
	       if (ssnValidationCode == null
		  || ssnValidationCode.equalsIgnoreCase("Game Over")
		  || !ssnValidationCode.equals(inputValidationCode)) {
			// 用户输入的值与看到的不一致,抛出异常
			httpServletRequest
                          .setAttribute("errorMsg", "验证码输入错误!");
			  throw new ValidationCodeException("验证码输入错误!");
               }
	    return super.attemptAuthentication(httpServletRequest);
	}
}

ValidationCodeException.java

import org.acegisecurity.AuthenticationException;

public class ValidationCodeException extends AuthenticationException {
 private static final long serialVersionUID = 1L;

 public ValidationCodeException(String s) {   
        super(s);   
    }
}

<bean id="authenticationProcessingFilter"
		class="com.uiiang.iknow.common.webapp.filter.ValidationCodeFilter">
		<property name="authenticationManager" ref="authenticationManager" />
		<property name="authenticationFailureUrl" value="/login.jsp?error=true" />
		<property name="defaultTargetUrl" value="/login.do" />
		<property name="filterProcessesUrl" value="/j_security_check" />
		<property name="alwaysUseDefaultTargetUrl" value="true" />
	</bean>