Get header from HttpUrlConnection object

Question

I want to send request to servlet and read headers from response. So I try it using this:

  URL url = new URL(contextPath + "file_operations");
    HttpURLConnection conn = null;
    try {
        conn = (HttpURLConnection) url.openConnection();
        conn.setDoOutput(true);
        conn.setDoInput(true);
        conn.setRequestMethod("POST");
        conn.setRequestProperty("charset", "utf-8");
        conn.setUseCaches(false);
        conn.setConnectTimeout(1000 * 5);
        conn.connect();

        conn.getHeaderField("MyHeader")
        .....

But received headers are always null. Servlet works fine (i tried work with servlet using standalone HTTP client)

Is it connecting or giving any exception ??

Deepu--Java
– Deepu--Java

2013-08-13 06:30:37 +00:00
Commented Aug 13, 2013 at 6:30 — Deepu--Java
– Deepu--Java, Commented Aug 13, 2013 at 6:30

ns16 · Accepted Answer · 2019-08-13 05:51:03Z

44

Make sure you are getting the successful response before you try to fetch the headers. This is how you can check for your response:

int status = conn.getResponseCode();

if (status == HttpURLConnection.HTTP_OK) {
    String header = conn.getHeaderField("MyHeader");
}

Also make sure the Servlet response is not a redirect response, if redirected all the session information, including headers will be lost.

edited Aug 13, 2019 at 5:51

ns16

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answered Aug 13, 2013 at 6:31

Juned Ahsan

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A-J-Bauer · Accepted Answer · 2017-06-29 09:29:39Z

20

Before the connect (right after setRquestPropert, setDoOutput a.s.o):

for (Map.Entry<String, List<String>> entries : conn.getRequestProperties().entrySet()) {    
    String values = "";
    for (String value : entries.getValue()) {
        values += value + ",";
    }
    Log.d("Request", entries.getKey() + " - " +  values );
}

Before disconnect (after reading response a.s.o):

for (Map.Entry<String, List<String>> entries : conn.getHeaderFields().entrySet()) {
    String values = "";
    for (String value : entries.getValue()) {
        values += value + ",";
    }
    Log.d("Response", entries.getKey() + " - " +  values );
}

answered Jun 29, 2017 at 9:29

A-J-Bauer

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