http://bbs.csdn.net/topics/390426978

public static String readCheckImage(HashMap<String, String> requestMap) {

        String url = requestMap.get("url");

        if (requestMap.get("params") != null) {

            url += "?" + requestMap.get("params");

        }

        InputStream in = null;

        try {

            System.out.println("get>>>" + url);

            URL serverUrl = new URL(url);

            HttpURLConnection conn = (HttpURLConnection) serverUrl.openConnection();

            conn.setRequestMethod("GET");// "POST" ,"GET"

            conn.addRequestProperty("Cookie", requestMap.get("cookie"));

            conn.addRequestProperty("Accept-Charset", "UTF-8;");// GB2312,

            conn.addRequestProperty("User-Agent",

                    "Mozilla/5.0 (Windows; U; Windows NT 5.1; zh-CN; rv:1.9.2.8) Firefox/3.6.8");

            conn.connect();

            // 判断请求是否成功

            if (((HttpURLConnection) conn).getResponseCode() == 200) {

                // 获取所有响应头字段

                Map<String, List<String>> map = conn.getHeaderFields();

                // 遍历所有的响应头字段

                for (String key : map.keySet()) {

                    System.out.println(key + "--->" + map.get(key));

                }

                // 返回的cookie

                String cookie = null;

                if (conn.getHeaderFields().get("Set-Cookie") != null) {

                    for (String s : conn.getHeaderFields().get("Set-Cookie")) {

                        cookie += s;

                    }

                }

                requestMap.put("cookie", requestMap.get("cookie") + cookie);

                in = conn.getInputStream();

                BufferedImage bi = ImageIO.read(in);

                File f = new File("check_img.jpg");

                ImageIO.write(bi, "jpg", f);

                return f.getAbsolutePath();

            } else {

                System.out.println("下载code图片失败！");

            }

        } catch (Exception e) {

            e.printStackTrace();

        }// 使用finally块来关闭输入流

        finally {

            try {

                if (in != null) {

                    in.close();

                }

            } catch (Exception e2) {

                e2.printStackTrace();

            }

        }

        return null;

    }