index.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
<script type="text/javascript">
function reloadCode() {
var time=new Date().getTime();
document.getElementById("imagecode").src="<%=request.getContextPath()%>/servlet/ImageServlet?d="+time;
}
</script>
</head>
<body>
<form action="<%=request.getContextPath()%>/servlet/LoginServlet" method="get">
验证码:<input type="text" name="checkcode"/>
<img alt="验证码" id="imagecode" src="<%=request.getContextPath()%>/servlet/ImageServlet"/>
<a href="javascript:reloadCode();">看不清楚</a><br>
<input type="submit" value="提交"/>
</form>
</body>
</html>
ImageServlet.java
package code;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.util.Random;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class ImageServlet extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response){
BufferedImage bi=new BufferedImage(68, 22, BufferedImage.TYPE_INT_RGB);
Graphics g=bi.getGraphics();
Color c=new Color(200,150,225);
g.setColor(c);
g.fillRect(0, 0, 68, 22);
char[] ch="ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890".toCharArray();
Random r=new Random();
int len=ch.length,index;
StringBuffer sb=new StringBuffer();
for(int i=0;i<4;i++) {
index=r.nextInt(len);
g.setColor(new Color(r.nextInt(88),r.nextInt(188),r.nextInt(255)));
g.drawString(ch[index]+"",(i*15)+3, 18);
sb.append(ch[index]);
}
}
}
web.xml
<servlet>
<servlet-name>ImageServlet</servlet-name>
<servlet-class>code.ImageServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>ImageServlet</servlet-name>
<url-pattern>/servlet/ImageServlet</url-pattern>
</servlet-mapping>
ImageServlet.java中最后缺少request.getSession().setAttribute("piccode", sb.toString());
ImageIO.write(bi, "JPG", response.getOutputStream());加上也没能显示