java - 每次都必须声明 HttpUrlConnection 吗？

Question

1

for(int i=0; i<3; i++)
    {
        URL url = new URL("http://localhost/network_test.php");
        HttpURLConnection connection = (HttpURLConnection) url.openConnection();

        DataOutputStream wr = new DataOutputStream(
                connection.getOutputStream ());
        wr.writeBytes("some data to send");
        wr.flush();
        wr.close();

        // prepare request to server

        // ...

        // recive data from server

        connection.disconnect();
    }

2

URL url = new URL("http://localhost/network_test.php");
HttpURLConnection connection = (HttpURLConnection) url.openConnection();

for(int i=0; i<3; i++)
    {
        DataOutputStream wr = new DataOutputStream(
                connection.getOutputStream ());
        wr.writeBytes("some data to send");
        wr.flush();
        wr.close();


        // prepare request to server

        // ...

        // recive data from server
    }

connection.disconnect();

第一个选项很完美!

但为什么我不能使用#2 版本？每次我都必须创建新对象 HttpUrlConnection 吗？为什么？

#2 版本错误:

java.net.ProtocolException: cannot write request body after response has been read

Answer 1

Instances of URLConnection are not reusable: you must use a different instance for each connection to a resource

-- http://developer.android.com/reference/java/net/URLConnection.html