src/com/inloam/common/RandImage.java

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package com.inloam.common;

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 RandImage extends HttpServlet {

 public RandImage() {
  super();
  
 }


 
 @Override
protected void doGet(HttpServletRequest req,HttpServletResponse res) throws IOException,ServletException{

//设置输出内容为图像，格式为jpeg
  res.setContentType("image/jpg");
  try {
//将内容输出到响应客户端对象的输出流中，生成的图片中包含6个字符

   String v = RandomGraphic.createInstance(4).drawAlpha(RandomGraphic.GRAPHIC_JPEG,res.getOutputStream());
//将字符串的值保留在session中，便于和用户手工输入的验证码比较，比较部分不是本文讨论重点，故略
   System.out.println("v:"+v);
   req.getSession().setAttribute("rv",v); 
  } catch (Exception e) {
   
   e.printStackTrace();
  }
  
 }


}