java - 输入流和 SAXParser 的问题

Question

当我使用 HTTPGET 特别是 TIMEOUT 处理并通过 HttpResponse 和 passto xmlR.parse(new InputSource(instream)) 获取响应时，我在解析时遇到了问题; 并制作休息程序。但有抛出错误:

05-08 11:03:38.637: WARN/System.err(522): java.io.IOException: Attempted read on closed stream.
05-08 11:03:38.667: WARN/System.err(522):     at org.apache.http.conn.EofSensorInputStream.isReadAllowed(EofSensorInputStream.java:127)
05-08 11:03:38.667: WARN/System.err(522):     at org.apache.http.conn.EofSensorInputStream.read(EofSensorInputStream.java:176)
05-08 11:03:38.677: WARN/System.err(522):     at org.apache.harmony.xml.ExpatParser.parseFragment(ExpatParser.java:515)
05-08 11:03:38.677: WARN/System.err(522):     at org.apache.harmony.xml.ExpatParser.parseDocument(ExpatParser.java:478)
05-08 11:03:38.677: WARN/System.err(522):     at org.apache.harmony.xml.ExpatReader.parse(ExpatReader.java:317)
05-08 11:03:38.677: WARN/System.err(522):     at org.apache.harmony.xml.ExpatReader.parse(ExpatReader.java:275)
05-08 11:03:38.677: WARN/System.err(522):     at com.housedisplay.mapspec.MyMapActivity.Sendsarchparameter(MyMapActivity.java:334)
05-08 11:03:38.687: WARN/System.err(522):     at com.housedisplay.mapspec.MyMapActivity.access$0(MyMapActivity.java:289)
05-08 11:03:38.697: WARN/System.err(522):     at com.housedisplay.mapspec.MyMapActivity$SearchATask.doInBackground(MyMapActivity.java:251)
05-08 11:03:38.697: WARN/System.err(522):     at com.housedisplay.mapspec.MyMapActivity$SearchATask.doInBackground(MyMapActivity.java:1)
05-08 11:03:38.697: WARN/System.err(522):     at android.os.AsyncTask$2.call(AsyncTask.java:252)
05-08 11:03:38.697: WARN/System.err(522):     at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
05-08 11:03:38.697: WARN/System.err(522):     at java.util.concurrent.FutureTask.run(FutureTask.java:137)
05-08 11:03:38.697: WARN/System.err(522):     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1081)
05-08 11:03:38.697: WARN/System.err(522):     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:574)
05-08 11:03:38.697: WARN/System.err(522):     at java.lang.Thread.run(Thread.java:1020)

代码::(超时代码基于this answer by kuester2000)

HttpGet httpGet = new HttpGet(strURL.toURI());
            HttpParams httpParameters = new BasicHttpParams();
            // Set the timeout in milliseconds until a connection is established.
            // The default value is zero, that means the timeout is not used. 
            int timeoutConnection = 3000;
            HttpConnectionParams.setConnectionTimeout(httpParameters, timeoutConnection);
            // Set the default socket timeout (SO_TIMEOUT) 
            // in milliseconds which is the timeout for waiting for data.
            int timeoutSocket = 5000;
            HttpConnectionParams.setSoTimeout(httpParameters, timeoutSocket);

            DefaultHttpClient httpClient = new DefaultHttpClient(httpParameters);
            HttpResponse response = httpClient.execute(httpGet);
            
            
            HttpEntity entity = response.getEntity();
            InputStream instream = entity.getContent();
            if (entity != null) {
                
                strResponse = convertStreamToString(instream);

                
            }
        /**********test*******/
            SAXParserFactory saxPF = SAXParserFactory.newInstance();
            
            SAXParser saxP = saxPF.newSAXParser();
            XMLReader xmlR = saxP.getXMLReader();
            System.out.println("url >>>>>" + strURL);
            HandlerFromLatLongCustom myXMLHandler = new HandlerFromLatLongCustom();
            xmlR.setContentHandler(myXMLHandler);
            xmlR.parse(new InputSource(instream));
            instream.close();

Answer 1

我怀疑这是问题所在:

strResponse = convertStreamToString(instream);

我的猜测是该方法(您尚未显示)会关闭流。撇开其他不谈，它至少会读取流，这将使以后很难再次读取...

您可以或者将整个响应读入一个字节数组，然后您可以根据需要将其包装在任意多个 ByteArrayInputStream 中，或者您可以使用 strResponse 作为解析源。不过，这可能会引发编码问题。

HttpClient 可能会为您完成所有这些 - 您可以简单地写:

instream = entity.getContent();

并再次获取相同的数据 - 我对返回的流是否有效“实时”或客户端代码是否读取数据并缓存数据的细节了解不够。

另请注意，这段代码非常可疑:

HttpEntity entity = response.getEntity();
InputStream instream = entity.getContent();
if (entity != null) {
    ...

如果 entity 为 null，第二行将已经抛出一个 NullPointerException，使得对第三行的检查变得毫无意义......