Java的Android的OutputStreamWriter IOException异常

Question

我有一个代码发送请求给PHP页面，它工作得很好，但突然（我不记得任何更改），它停止工作无论在模拟器和真实设备

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"); 

这里是堆栈跟踪：

 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) 

Answer 1

查看源代码，当doOutput未设置为true该异常被抛出：

（来源：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"); 
    } 

的HttpURLConnectionImpl类是从Java的HttpUrlConnection延伸URLConnection类扩展。看着你找到Javadoc中：

保护布尔则将DoOutput

此变量由setDoOutput 方法设置。它的值由getDoOutput方法返回。一个URL 连接可用于输入和/或输出。将doOutput 标志设置为true表示应用程序打算将数据写入到 的URL连接。

此字段的默认值为false。

所以，你需要做的：

httpConn.setDoOutput(true); 

在你的代码。