java - Java Android OutputStreamWriter IOException

我有一个代码将请求发送到php页面，并且工作正常，但突然（我不记得更改任何内容），它在模拟器和实际设备上均停止工作

    URL url = new URL(this.site);
            URLConnection conn = url.openConnection();

            if (!(conn instanceof HttpURLConnection))    {
                Log.e(TAG, "connection is not HttpURLConnection");
                throw new IOException("Not an HTTP connection");

            }

            try{
                Log.e(TAG, "Trying");
                HttpURLConnection httpConn = (HttpURLConnection) conn;
                Log.e(TAG, "Created connection");
                httpConn.setAllowUserInteraction(false);
                httpConn.setInstanceFollowRedirects(true);
                httpConn.setRequestMethod("POST");
                Log.e(TAG, "connecting");
                httpConn.connect();
                Log.e(TAG, "connected");

                OutputStreamWriter wr = new OutputStreamWriter(httpConn.getOutputStream());
                Log.e(TAG, "created outputstream");

这是堆栈跟踪：

     12-25 00:32:14.024: W/System.err(885): java.net.ProtocolException: Does not support output
     12-25 00:32:14.090: W/System.err(885):     at org.apache.harmony.luni.internal.net.www.protocol.http.HttpURLConnectionImpl.getOutputStream(HttpURLConnectionImpl.java:575)
     12-25 00:32:14.090: W/System.err(885):     at com.*****.StringAsyncRetriever.OpenHttpConnection(StringAsyncRetriever.java:122)
     12-25 00:32:14.090: W/System.err(885):     at com.******.StringAsyncRetriever.getData(StringAsyncRetriever.java:66)
     12-25 00:32:14.094: W/System.err(885):     at com.******.StringAsyncRetriever.doInBackground(StringAsyncRetriever.java:38)
     12-25 00:32:14.094: W/System.err(885):     at com.******.StringAsyncRetriever.doInBackground(StringAsyncRetriever.java:1)
     12-25 00:32:14.094: W/System.err(885):     at android.os.AsyncTask$2.call(AsyncTask.java:185)
     12-25 00:32:14.094: W/System.err(885):     at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:306)
     12-25 00:32:14.094: W/System.err(885):     at java.util.concurrent.FutureTask.run(FutureTask.java:138)
     12-25 00:32:14.094: W/System.err(885):     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1088)
     12-25 00:32:14.094: W/System.err(885):     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:581)
     12-25 00:32:14.094: W/System.err(885):     at java.lang.Thread.run(Thread.java:1019)

最佳答案

查看源代码，当doOutput未设置为true时抛出该异常：

（来自：http://www.java2s.com/Open-Source/Android/android-core/platform-libcore/org/apache/harmony/luni/internal/net/www/protocol/http/HttpURLConnectionImpl.java.htm）

public OutputStream getOutputStream() throws IOException {
    if (!doOutput) {
        throw new ProtocolException("Does not support output");
    }

HttpURLConnectionImpl类是从Java的HttpUrlConnection类扩展的，该类扩展了URLConnection。查看您发现的javadocs：


  受保护的布尔值doOutput
  
  此变量由setDoOutput设置
  方法。其值由getDoOutput方法返回。网址
  连接可用于输入和/或输出。设置doOutput
  标记为true表示应用程序打算将数据写入
  URL连接。
  
  该字段的默认值为false。


因此，您需要执行以下操作：

httpConn.setDoOutput(true);

在您的代码中。