java - 如何处理Java AssertionError(java.lang.SocketException)？

Question

我有 Android 应用程序，它从服务器中提取 xml。

public class FeedParser {

    private final URL mURL;

    public FeedParser(String feedUrl) {
        try {
            mURL = new URL(feedUrl);
        } catch (MalformedURLException e) {
            throw new RuntimeException();
        }
    }

    private InputStream getInputStream() throws IOException {
        return mURL.openConnection().getInputStream();
    }

    public FeedItem parseFeed() {
        // SAX stuff here

        try {
            Xml.parse(getInputStream(), Xml.Encoding.UTF_8,
                    root.getContentHandler());
        } catch (Exception e) {
            e.printStackTrace();
        }
        return result;
    }
}

有时，当 XML.parse(...) 执行时，我得到异常:

 AndroidRuntime: java.lang.RuntimeException: An error occured while executing doInBackground()
 AndroidRuntime:    at android.os.AsyncTask$3.done(AsyncTask.java:200)
 AndroidRuntime:    at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:274)
 AndroidRuntime:    at java.util.concurrent.FutureTask.setException(FutureTask.java:125)
 AndroidRuntime:    at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:308)
 AndroidRuntime:    at java.util.concurrent.FutureTask.run(FutureTask.java:138)
 AndroidRuntime:    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1088)
 AndroidRuntime:    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:581)
 AndroidRuntime:    at java.lang.Thread.run(Thread.java:1019)
 AndroidRuntime: Caused by: java.lang.AssertionError: java.net.SocketException: Connection reset by peer
 AndroidRuntime:    at android.util.Xml.parse(Xml.java:89)
 AndroidRuntime:    at com.packagename.FeedParser.parseFeed(FeedParser.java:60)
 AndroidRuntime:    at com.packagename.UpdateService$FeedLookupTask.doInBackground(UpdateService.java:84)
 AndroidRuntime:    at com.packagename.UpdateService$FeedLookupTask.doInBackground(UpdateService.java:1)
 AndroidRuntime:    at android.os.AsyncTask$2.call(AsyncTask.java:185)
 AndroidRuntime:    at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:306)
 AndroidRuntime:    ... 4 more
 AndroidRuntime: Caused by: java.net.SocketException: Connection reset by peer
 AndroidRuntime:    at org.apache.harmony.luni.platform.OSNetworkSystem.read(Native Method)
 AndroidRuntime:    at dalvik.system.BlockGuard$WrappedNetworkSystem.read(BlockGuard.java:273)
 AndroidRuntime:    at org.apache.harmony.luni.net.PlainSocketImpl.read(PlainSocketImpl.java:458)
 AndroidRuntime:    at org.apache.harmony.luni.net.SocketInputStream.read(SocketInputStream.java:85)
 AndroidRuntime:    at org.apache.harmony.luni.net.SocketInputStream.read(SocketInputStream.java:65)
 AndroidRuntime:    at java.io.BufferedInputStream.fillbuf(BufferedInputStream.java:140)
 AndroidRuntime:    at java.io.BufferedInputStream.read(BufferedInputStream.java:225)
 AndroidRuntime:    at org.apache.harmony.luni.internal.net.www.protocol.http.HttpURLConnectionImpl.readLine(HttpURLConnectionImpl.java:660)
 AndroidRuntime:    at org.apache.harmony.luni.internal.net.www.protocol.http.ChunkedInputStream.readChunkSize(ChunkedInputStream.java:77)
 AndroidRuntime:    at org.apache.harmony.luni.internal.net.www.protocol.http.ChunkedInputStream.read(ChunkedInputStream.java:45)
 AndroidRuntime:    at java.io.InputStream.read(InputStream.java:157)
 AndroidRuntime:    at org.apache.harmony.xml.ExpatParser.parseFragment(ExpatParser.java:516)
 AndroidRuntime:    at org.apache.harmony.xml.ExpatParser.parseDocument(ExpatParser.java:479)
 AndroidRuntime:    at org.apache.harmony.xml.ExpatReader.parse(ExpatReader.java:318)
 AndroidRuntime:    at org.apache.harmony.xml.ExpatReader.parse(ExpatReader.java:275)

如何处理此类错误？

编辑 知道捕获错误是糟糕的编程风格，我寻求更优雅的解决方案。

Answer 1

Connection reset by peer 意味着你正在读取的远程服务器正在关闭连接，然后你试图再次从它读取。远程端执行此操作不一定是网络错误——它可以出于多种原因执行此操作。在不知道服务器协议(protocol)的情况下，很难知道确切的原因。

您可以将代码设置为捕获并重试有限次数，如上文所建议。捕获错误不是一个坏主意。

根据您的 xml 的大小，另一种可能性是将其读入字符串缓冲区，然后对其进行解析。对于大数据，这会降低重置的可能性，因为您的服务器连接将比您在进行解析时短得多。我在这里想到一个场景，在你解析时 tcp 窗口关闭了很长时间，最终对方认为你已经死了并重置连接。