Why the code throws "Cannot write output after reading input" error?

Question

Please check the code below. What the code does is use firstHttpConn to check the response code and open secondHttpConn. If the response code is 401, add a basic auth header to secondHttpConn. Then post the data and read the response.

However, the code throws Cannot write output after reading input error. I checked other questions on Stack Overflow like this one and I am sure I did not make the same mistakes.

//I hate using Java 6 and HttpURLConnection, but the code is for a very old system.
private static XmlObject callWebService(String soapMessage, String webServiceEndpoint, String soapAction) throws Exception {
    XmlObject resultXMLObject;
    HttpURLConnection firstHttpConn = null;
    HttpURLConnection secondHttpConn = null;

    try {
        byte[] streamoutByteArray = soapMessage.getBytes("UTF-8");

        URL url = new URL(webServiceEndpoint);
        firstHttpConn = (HttpURLConnection) url.openConnection();
        firstHttpConn.connect();

        if (firstHttpConn.getResponseCode() == 401) {
            firstHttpConn.disconnect();
            secondHttpConn = (HttpURLConnection) url.openConnection();
            secondHttpConn.setRequestProperty("Authorization", "Basic " + getBasicAuth());
        } else {
            firstHttpConn.disconnect();
            secondHttpConn = (HttpURLConnection) url.openConnection();
        }

        secondHttpConn.setConnectTimeout(30000);
        secondHttpConn.setReadTimeout(300000);
        secondHttpConn.setRequestProperty("Content-Length", String.valueOf(streamoutByteArray.length));
        secondHttpConn.setRequestProperty("Content-Type", "text/xml; charset=UTF-8);
        secondHttpConn.setRequestProperty("SOAPAction", soapAction);
        secondHttpConn.setRequestMethod("POST");
        secondHttpConn.setDoOutput(true);
        secondHttpConn.setDoInput(true);

        OutputStream out = secondHttpConn.getOutputStream();
        out.write(streamoutByteArray);
        out.close();

        //Line 238 below.
        InputStreamReader isr = new InputStreamReader(secondHttpConn.getInputStream());
        BufferedReader in = new BufferedReader(isr);
        String inputLine;
        StringBuffer sb = new StringBuffer();

        while ((inputLine = in.readLine()) != null)
            sb.append(inputLine).append("\n");

        in.close();
        resultXMLObject = XmlObject.Factory.parse(sb.toString());
    } finally {
        if (firstHttpConn != null)
            firstHttpConn.disconnect();
        if (secondHttpConn != null)
            secondHttpConn.disconnect();
    }

    return resultXMLObject;
}

The log:

Caused By: java.net.ProtocolException: Cannot write output after reading input.
        at weblogic.net.http.HttpURLConnection.getOutputStream(HttpURLConnection.java:271)
        at org.company.member.esb.webservice.WebServiceClient.callWebService(WebServiceClient.java:238)
        at org.company.member.esb.webservice.WebServiceClient.invokeWebserviceV01(WebServiceClient.java:132)
        at sun.reflect.GeneratedMethodAccessor711.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        Truncated. see log file for complete stacktrace

Anyone knows why? Thanks.

@luk2302 I don't think it matters because I added `connect()` before and it threw the same error. — 6324, Oct 02 '17 at 15:55
Ah, I overlooked that you created a second connection. Sorry. Now I do not know of the top of my head what might be wrong. You should probably add the stacktrace you receive to the question. — luk2302, Oct 02 '17 at 15:58
The exception is thrown at `weblogic.net.http.HttpURLConnection.getOutputStream` I don't see how it's possible that it's thrown at the line you showed which gets the `InputStream` — Oleg, Oct 02 '17 at 16:14
@Oleg Yeah it is weird because line 238 points to the line which gets the `InputStream.` — 6324, Oct 02 '17 at 16:15
Perhaps because `url` is re-used. Try creating a new instance: `secondHttpConn = (HttpURLConnection) (new URL(webServiceEndpoint)).openConnection();` — Andrew S, Oct 02 '17 at 16:17
@Oleg I also want to debug. But the code is "older than my grandpa" and I am not able to set it up running it on my laptop. I have to deploy it to the old system to run every time, which takes 2 hours or so. — 6324, Oct 02 '17 at 16:21
@YilongWang you can always just isolate a small block of code like the one in the question and just run that, anywhere. — eis, Oct 02 '17 at 16:22

score 0 · Accepted Answer · answered Oct 02 '17 at 16:19

0

You're not running the code you pasted here. You can see the lines do not match, as there is HttpURLConnection.getOutputStream in the stack trace, but you claim

//Line 238 below.
InputStreamReader isr = new InputStreamReader(secondHttpConn.getInputStream());

so code is different for stack trace and your paste.

I don't see a problem with the code you've pasted here.

answered Oct 02 '17 at 16:19

eis

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I do think the code matches. Let me isolate the code and run that on my local machine. – 6324 Oct 02 '17 at 16:23
2

it's not a matter of opinion, that line does not call getOutputStream() so it does not match. – eis Oct 02 '17 at 16:25
Yes you are right. The grandpa system did not pick up my latest code. It took me some time to find it out. :) – 6324 Oct 04 '17 at 21:35

Why the code throws "Cannot write output after reading input" error?

1 Answers1