android httpclient 工作，但我类似的 HttpUrlconnection 不工作 post

Question

你们中的许多人都知道新应用程序应该使用 HttpUrlconnection，因为 Httpclient 将无法工作超过 api 22. 我在 HttpClient 中有以下代码成功 posts 到服务器然后我评论说出并换入 HttpUrlconnection，它不会 post。我的 HttpUrlconnection

代码可能有什么问题

    URL url = new URL(LOGIN_URL);
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        conn.connect();
        conn.setReadTimeout(10000);
        conn.setConnectTimeout(15000);
        conn.setRequestMethod("POST");
       String cert="username=user_777&password=76566";
        conn.setDoOutput(true);
        DataOutputStream wr = new DataOutputStream(conn.getOutputStream());
        wr.writeBytes(cert);
        wr.flush();
        wr.close();

      conn.disconnect();

HttpClient 中的这段类似代码完美运行

 HttpClient httpClient = new DefaultHttpClient();
        HttpPost httpPost = new HttpPost(LOGIN_URL);
        List<NameValuePair> nameValuePair = new ArrayList<NameValuePair>(2);
        nameValuePair.add(new BasicNameValuePair("username", "test_user"));
        nameValuePair.add(new BasicNameValuePair("password", "123456789"));
        httpPost.setEntity(new UrlEncodedFormEntity(nameValuePair));
        HttpResponse response = httpClient.execute(httpPost);
        Log.d("Http Post Response:", response.toString());

Httpclient 工作，HttpUrlclient 不工作我怎样才能让它工作？他们都有相同的 URL.

Answer 1

问题是您在连接已打开时调用 conn.setDoOutput(true)。

来自the documentation：

Sets the flag indicating whether this URLConnection allows output. It cannot be set after the connection is established.

将对 conn.setDoOutput(true); 的调用移至 conn.connect(); 之前解决了该问题。

这是我在使用您的原始代码时遇到的错误：

 java.lang.RuntimeException: An error occured while executing doInBackground()
            at android.os.AsyncTask.done(AsyncTask.java:300)
            at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:355)
            at java.util.concurrent.FutureTask.setException(FutureTask.java:222)
            at java.util.concurrent.FutureTask.run(FutureTask.java:242)
            at android.os.AsyncTask$SerialExecutor.run(AsyncTask.java:231)
            at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
            at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
            at java.lang.Thread.run(Thread.java:841)
     Caused by: java.lang.IllegalStateException: Already connected
            at java.net.URLConnection.checkNotConnected(URLConnection.java:464)
            at java.net.URLConnection.setDoOutput(URLConnection.java:878)

这是完整的工作和测试代码，注意我添加了一些 try/catch 块并稍微移动了一些东西，还添加了代码以从服务器读取结果：

class MyAsyncTask extends AsyncTask<String, String, String> {

    String LOGIN_URL = "http://www.example.com/someFile.php";
    HttpURLConnection conn;
    DataOutputStream wr;
    StringBuilder result = new StringBuilder();
    URL url;

    @Override
    protected String doInBackground(String... params) {

        try {
            url = new URL(LOGIN_URL);

            conn = (HttpURLConnection) url.openConnection();

            conn.setDoOutput(true); //moved here

            conn.connect();

        } catch (IOException e) {
            e.printStackTrace();
        }

        conn.setReadTimeout(10000);
        conn.setConnectTimeout(15000);
        try {
            conn.setRequestMethod("POST");
        } catch (ProtocolException e) {
            e.printStackTrace();
        }
        String cert="name=user_777&message=7656666666";


        try {
            wr = new DataOutputStream(conn.getOutputStream());
            wr.writeBytes(cert);
            wr.flush();
            wr.close();

            InputStream in = new BufferedInputStream(conn.getInputStream());
            BufferedReader reader = new BufferedReader(new InputStreamReader(in));

            String line;
            while ((line = reader.readLine()) != null) {
                result.append(line);
            }

        } catch (IOException e) {
            e.printStackTrace();
        }


        conn.disconnect();

        return result.toString();
    }

    @Override
    protected void onPostExecute(String result) {

        Toast.makeText(MainActivity.this, result, Toast.LENGTH_LONG ).show();
    }
}

android httpclient 工作，但我类似的 HttpUrlconnection 不工作 post

android httpclient works but my similar HttpUrlconnection does not post

java

android

httpurlconnection