Web.xml文件

<?xml version="1.0" encoding="UTF-8"?>

<web-app version="2.5"

    xmlns="http://java.sun.com/xml/ns/javaee"

    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee

    http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">

  <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>GetCheckCode</servlet-name>

    <servlet-class>GetCheckCode</servlet-class>

  </servlet>

  <servlet-mapping>

    <servlet-name>GetCheckCode</servlet-name>

    <url-pattern>/checkcode</url-pattern>

  </servlet-mapping>

  <welcome-file-list>

    <welcome-file>index.jsp</welcome-file>

  </welcome-file-list>

</web-app>

Servlet文件

import java.awt.Graphics;

import java.awt.image.BufferedImage;

import java.io.IOException;

import java.io.OutputStream;

import javax.imageio.ImageIO;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

public class GetCheckCode extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)

           throws ServletException, IOException {

           doPost(request, response);

    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)

           throws ServletException, IOException {

           response.setContentType("image/JPEG");

           int width=80;

           int height=15;

           BufferedImage bi=new BufferedImage(width, height,BufferedImage.TYPE_INT_RGB);

           Graphics g=bi.getGraphics();

           g.drawString("hello",15,9);

           g.dispose();

           OutputStream os=response.getOutputStream();

           ImageIO.write(bi, "JPEG",os);

           os.flush();

           os.close();

    }

}