JAVA代码模拟获取cookie以及携带cookie

去年做android的时候，网络连接没有用类似OKHttp之类的框架，而是完全用jdk自带的api实现，今天不想看书。。就把笔记整理一下吧。。

这里有个小demo，是先实现登陆，登陆的过程是通过post方式请求，登陆后通过携带的cookie判断是否已经成功登陆。

1.获取cookie

public void connect(String u) throws IOException{
        HttpURLConnection conn = null;
        OutputStream os = null;
        InputStream is = null;
        try {
            URL url = new URL(u);
            conn = (HttpURLConnection) url.openConnection();
            conn.setRequestMethod("POST");
            conn.setDoInput(true);
            conn.setDoOutput(true);
            os = conn.getOutputStream();
            String param = "account=senninha&password=senninha";
            String eparam = param;
            //这里是把post参数携带上去。
            os.write(eparam.getBytes("utf-8"));
            is = conn.getInputStream();
            byte[] b = new byte[1024];
            int len = is.read(b);
            while(len != -1){
                System.out.println(new String(b,0,len,"utf-8"));
                len = is.read(b);
            }
            //这里是读取第一次登陆时服务器返回的cookie，然后用一个全局变量cookie接收。因为是服务器往客户端发送cookie，所以名字是Set-Cookie
            cookie = conn.getHeaderField("Set-Cookie");
            System.out.println("read over" + cookie);
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }   finally{
            if(os != null){
                os.close();
            }
            
            if(is != null){
                is.close();
            }
            if(conn != null){
                conn.disconnect();
            }
            
            System.out.println("all close");
        }
    }

2.携带cookie

public void isLogin(String u) throws IOException{
        HttpURLConnection conn = null;
        InputStream is = null;
        try {
            URL url = new URL(u);
            conn = (HttpURLConnection) url.openConnection();
            conn.setRequestMethod("POST");
            //把上一步获取的cookie携带上去
            conn.setRequestProperty("cookie", cookie);
            conn.setDoInput(true);
            is = conn.getInputStream();
            byte[] b = new byte[1024];
            int len = is.read(b);
            while(len != -1){
                System.out.println(new String(b,0,len,"utf-8"));
                len = is.read(b);
            }
            System.out.println("read over");
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }   finally{
            if(is != null){
                is.close();
            }
            if(conn != null){
                conn.disconnect();
            }
            
        }
            System.out.println("all close");
        }

ok，以后每次访问，只要携带上这个cookie，就可以畅通无阻了。当然，是指用cookie维持登陆的网站。

ps：java后端的维持登陆状态的cookie叫JSESSIONID，php的叫phpSessionId好像。。
ps：对于安卓客户端来说，获取到的cookie可以存到数据库里，这样重启app后一样可以再次保持登陆状态。