Android HttpUrlConnection result string truncated

Question

I am currently developing an Android application and encounter the following problem. I am making an HTTP request to a server that is supposed to send me back XML content that I then parse. I noticed recurring errors while parsing long XML strings so I decided to display the result of my requests and discovered that the string (or the stream?) that I receive is randomly truncated. Sometimes I get the whole string, sometimes half, sometimes a third, and it seems to follow a certain pattern in the amount of characters that are truncated, what I mean by that is that I sometimes get 320 characters after a request then 156 after the next then 320 twice, then 156 again (these aren't the actual numbers but it follows a pattern).

Here is my code for the request and conversion of the InputStream into a string:

private String downloadUrlGet(String myurl) throws IOException {
    InputStream is = null;
    // Only display the first 20000 characters of the retrieved
    // web page content.
    int len = 20000;

    try {
        URL url = new URL(myurl);
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        conn.setReadTimeout(10000 /* milliseconds */);
        conn.setConnectTimeout(15000 /* milliseconds */);
        conn.setRequestMethod("GET");
        conn.setDoInput(true);
        conn.setRequestProperty("Content-Type", "application/xml");
        // Starts the query
        conn.connect();
        int response = conn.getResponseCode();
        Log.d(DEBUG_TAG, "The response is: " + response);
        is = conn.getInputStream();

        // Convert the InputStream into a string
        String contentAsString = readIt(is, len);
        return contentAsString;

    // Makes sure that the InputStream is closed after the app is
    // finished using it.
    } finally {
        if (is != null) {
            is.close();
        } 
    }
}

// Reads an InputStream and converts it to a String.
private String readIt(InputStream stream, int len) throws IOException, UnsupportedEncodingException {
    Reader reader = null;
    reader = new InputStreamReader(stream, "UTF-8");        
    char[] buffer = new char[len];
    reader.read(buffer);
    return new String(buffer);
}

The length of the XML that I try to retrieve is much less than 20000. I tried to use HttpURLConnection.setChunkedStreamingMode() with 0 and various other numbers as parameter but it didn't change anything.

Thanks in advance for any suggestions.

in your "readIt" your read input stream just one time, getting small chunk of data from buffer. You need to repeat reading it until it ends. — Alex Salauyou
– Alex Salauyou, Commented Mar 27, 2014 at 23:30

user207421 · Accepted Answer · 2014-03-27 23:26:54Z

2

You are making the usual mistake of assuming that read() fills the buffer. See the Javadoc. It isn't obliged to do that. It isn't obliged to transfer more than one byte as a matter of fact. You need to read in a loop until you have encountered end of stream (read() returns -1).

answered Mar 27, 2014 at 23:26

user207421

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3 Comments

Anthony Weibel Over a year ago

Thanks, I managed to make it work by reading the stream one character at a time and appending it to a String but I still can't figure out how to make it work using a buffer and read(char[] buffer, int offset, int count) like they do it in the official Android tutorial...

user207421 Over a year ago

while ((count = in.read(buffer)) > 0) { str += new String(buffer, 0, count); }

Pieter van Ginkel Over a year ago

The above method of reading a string is wrong if you're using multi-byte encoding (e.g. UTF-8). If the buffer ends half way a multi-byte character, this will throw. Instead use a StreamReader or something like that.

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