HttpURLConnection throws NullPointerException at getResponseCode

Question

My POST request throws a NullPointerException at getResponseCode(), however, it worked well till today. An equivalent curl call works as it should, so the problem should be in Java. The same implementation (without some properties, of course) works well for GET requests. Here it is:

private Object executeRequest(URL url, String httpMethod, String contentType, URL jobPropsPath)
            throws NoSuchAlgorithmException, KeyManagementException,
            MalformedURLException, IOException, ParseException {

        if(contentType == null) {
            contentType = "application/json";
        }

        // curl -k
        TrustManager[] trustAllCerts = { new OozieWorkflowTest.CustomX509TrustManager() };
        SSLContext sc = SSLContext.getInstance("SSL");
        sc.init(null, trustAllCerts, new SecureRandom());
        HttpsURLConnection.setDefaultSSLSocketFactory(sc.getSocketFactory());

        HostnameVerifier allHostsValid = (hostname, session) -> true;
        HttpsURLConnection.setDefaultHostnameVerifier(allHostsValid);

        // execute a request
        HttpsURLConnection conn = (HttpsURLConnection) url.openConnection();
        conn.setRequestProperty("Content-Type", contentType);
        conn.setRequestMethod(httpMethod);
        conn.setConnectTimeout(30000);

        // prepare request body (for XML only)
        if( (jobPropsPath != null) && ("POST".equals(httpMethod)) ) {
            File jobPropsXml = new File(jobPropsPath.getPath());

            if(jobPropsXml.exists()) {
                String jobPropsSerialized = this.serializeXml(jobPropsXml);
                conn.setDoOutput(true);

                // Add serialized String to a request body
                try(OutputStream output = new BufferedOutputStream(conn.getOutputStream())) {
                    output.write(jobPropsSerialized.getBytes());
                    output.flush();
                }

            } else {
                throw new IOException("Requested file does not exist in specified path.");
            }
        }

        // Process response
        int status = conn.getResponseCode();
        StringBuilder sb = new StringBuilder();

        switch (status) {
        ...
        }

        conn.disconnect();
        return new JSONParser().parse(sb.toString());
}

And here is the equivalent curl call (for more clarity)

curl -i -k --negotiate -u : -X POST -H "Content-Type: application/xml" -d foo/bar/wf.xml "https://host:port/oozie/v1/jobs"

Stack trace:

java.lang.RuntimeException: java.lang.NullPointerException

    at sun.net.www.protocol.http.HttpURLConnection.getInputStream0(HttpURLConnection.java:1488)
    at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1474)
    at sun.net.www.protocol.http.HttpURLConnection.getHeaderField(HttpURLConnection.java:3018)
    at java.net.HttpURLConnection.getResponseCode(HttpURLConnection.java:489)
    at sun.net.www.protocol.https.HttpsURLConnectionImpl.getResponseCode(HttpsURLConnectionImpl.java:338)
    at foo.bar.proj.OozieWorkflowTest.executeRequest(OozieWorkflowTest.java:193)
    at foo.bar.proj.OozieWorkflowTest.testWorkflowOverRestApi(OozieWorkflowTest.java:120)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at junit.framework.TestCase.runTest(TestCase.java:176)
    at junit.framework.TestCase.runBare(TestCase.java:141)
    at junit.framework.TestResult$1.protect(TestResult.java:122)
    at junit.framework.TestResult.runProtected(TestResult.java:142)
    at junit.framework.TestResult.run(TestResult.java:125)
    at junit.framework.TestCase.run(TestCase.java:129)
    at junit.framework.TestSuite.runTest(TestSuite.java:252)
    at junit.framework.TestSuite.run(TestSuite.java:247)
    at org.junit.internal.runners.JUnit38ClassRunner.run(JUnit38ClassRunner.java:86)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:115)
    at org.junit.vintage.engine.execution.RunnerExecutor.execute(RunnerExecutor.java:42)
    at java.util.stream.ForEachOps$ForEachOp$OfRef.accept(ForEachOps.java:184)
    at java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:193)
    at java.util.Iterator.forEachRemaining(Iterator.java:116)
    at java.util.Spliterators$IteratorSpliterator.forEachRemaining(Spliterators.java:1801)
    at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:481)
    at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:471)
    at java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:151)
    at java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:174)
    at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
    at java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:418)
    at org.junit.vintage.engine.VintageTestEngine.executeAllChildren(VintageTestEngine.java:83)
    at org.junit.vintage.engine.VintageTestEngine.execute(VintageTestEngine.java:74)
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:170)
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:154)
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:90)
    at com.intellij.junit5.JUnit5IdeaTestRunner.startRunnerWithArgs(JUnit5IdeaTestRunner.java:74)
    at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
    at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
    at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
Caused by: java.lang.NullPointerException
    at java.util.Base64$Encoder.encode(Base64.java:261)
    at java.util.Base64$Encoder.encodeToString(Base64.java:315)
    at sun.net.www.protocol.http.NegotiateAuthentication.setHeaders(NegotiateAuthentication.java:182)
    at sun.net.www.protocol.http.HttpURLConnection.getInputStream0(HttpURLConnection.java:1731)
    at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1474)
    at java.net.HttpURLConnection.getResponseCode(HttpURLConnection.java:480)
    ... 38 more

Answer 1

The error was due to some syntactical errors in the XML file that was sent with the request, so that the whole request could not be processed correctly. However, the curl request returned at least 400, whereas Java didn't get any response at all. I created a bug report, but there's no big chances, since the API is private and it's hard to reproduce this behaviour otherwise.