百度可以百度出来,这里做一点补充说明 原理:第一次交互时,记录对方返回的sessionid,下次再发送时加上次sessionid即可. 本次遇到的问题是,html页面访问后台1,后台1再通过http调用后台2. 此时html1访问后台1,有一个sessionid1,再调用后台2,此时会返回一个sessionid2给后台1 后台1中需要处理一下2个sessionid.当前台传来的是sessionid1,就去sessionid2发送给后台2 需要注意的地方,也是网上说的不清楚的地方.传给后台后总sessionid内容,不仅仅是sessionid值,应该为:JSESSIONID=023283505AAA8F227D29AD4A4256A555这整个字符串 以下代码为发送http请求的通用代码

private static Map<String, String> appSessionMap=new HashMap<String, String>();

 public static String sendPost(String url, Map<String,String> map,String value,HttpServletRequest request) {

        //为支持https访问
        HttpsURLConnection.setDefaultHostnameVerifier(new SendHTTP().new NullHostNameVerifier()); 
        SSLContext sc = null;
        try {
            sc = SSLContext.getInstance("TLS");
        } catch (NoSuchAlgorithmException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        } 
        try {
            sc.init(null, trustAllCerts, new SecureRandom());
        } catch (KeyManagementException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        } 
        HttpsURLConnection.setDefaultSSLSocketFactory(sc.getSocketFactory());



        PrintWriter out = null;
        BufferedReader in = null;
        String result = "";
        try {
            String param="";

            if(value!=null){
                param=value;
            }else if(map!=null){
                Set<Entry<String, String>> set=map.entrySet();
                Iterator<Entry<String, String>> it=set.iterator();
                while(it.hasNext()){
                    Entry<String, String> en=it.next();
                    if(!param.equals("")){
                        param+="&";
                    }
                    param+=en.getKey()+"="+URLEncoder.encode(en.getValue(),"UTF-8");
                }
            }
            URL realUrl = new URL(url);
            // 打开和URL之间的连接
            URLConnection conn = realUrl.openConnection();
            // 设置通用的请求属性
            conn.setRequestProperty("accept", "*/*");
            conn.setRequestProperty("connection", "Keep-Alive");
            conn.setRequestProperty("user-agent","Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");
            if(request!=null&&appSessionMap.containsKey(request.getSession().getId())){
                conn.setRequestProperty("Cookie", appSessionMap.get(request.getSession().getId()));
            }
            // 发送POST请求必须设置如下两行
            conn.setDoOutput(true);
            conn.setDoInput(true);
            // 获取URLConnection对象对应的输出流
            out = new PrintWriter(conn.getOutputStream());
            // 发送请求参数
            out.print(param);
            // flush输出流的缓冲
            out.flush();

            // 定义BufferedReader输入流来读取URL的响应
            in = new BufferedReader(new InputStreamReader(conn.getInputStream(),"UTF-8"));
            String line;
            while ((line = in.readLine()) != null) {
                result += line;
            }
            if(request!=null&&!appSessionMap.containsKey(request.getSession().getId())){
                appSessionMap.put(request.getSession().getId(), conn.getHeaderField("Set-Cookie").split(";")[0]);
            }
//            System.out.println(appSessionMap);
//            System.out.println("发送数据后返回数据:"+result);
//            result="<success>success</success>";
        } catch (Exception e) {
            System.out.println("发送 POST 请求出现异常！");
            result="sendError";
//            e.printStackTrace();
        }
        //使用finally块来关闭输出流、输入流
        finally{
            if(out!=null){
                out.close();
            }
            if(in!=null){
                try {
                    in.close();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
        }
        return result;
    }