[BUG] 8371092: NullPointerException in AltServiceUsageTest.afterClass test method

Overview#

In the AltServiceUsageTest class for the net system, a field named DatagramChannel udpNotResponding is retained during initialization¹. This DatagramChannel is closed at the end of the test (i.e., when the test class is destroyed)².

Under normal circumstances, the flow is preparation of origin and alternative servers → creation of channels → testing → destruction of channels, with no particular issues.

However, on line 85³, if the addresses of the origin server and the alternative server are identical, the channel is not prepared (=not initialized). In this case, since the channel remains uninitialized, there is a risk that a NullPointerException will occur when attempting to close it⁴.

Discovered on JBS in 2026/11/02#

This bug was discovered on JBS and verified locally. The suspected bug was reproduced, so I began working on the fix.

The following method is where the issue lies⁵:

@AfterClass
public void afterClass() throws Exception {
    safeStop(originServer);
    safeStop(altServer);
    udpNotResponding.close();
}

To address this problem, a null check was added to this part. Since udpNotResponding.close(); is called in other places as well, I created a common helper method and called it. This change has been marked as integrable.

private static void safeStop(final HttpTestServer server) {
    if (server == null) {
        return;
    }
    final InetSocketAddress serverAddr = server.getAddress();
    try {
        System.out.println("Stopping server " + serverAddr);
        server.stop();
    } catch (Exception e) {
        System.err.println("Ignoring exception: " + e.getMessage() + " that occurred during stop of server: " + serverAddr);
    }
}

By introducing this change and replacing the call site, I completed the fix⁶.

Reviewed on 2025/11/03#

The changes were reviewed by Daniel Fuchs⁷ who approved them. Additionally, he provided the following comment:

Please make sure to run the test locally before integrating. Networking tests are not run by github actions.

Integration Requested on 2025/11/04#

After confirming the previous review and running local tests, I verified that they passed and marked them as integrable.

Integrated on 2025/11/05#

With Fuchs⁷'s /sponsor, the changes were integrated into JDK under commit 2f455ed⁸.

Overview#

Discovered on JBS in 2026/11/02#

Reviewed on 2025/11/03#

Integration Requested on 2025/11/04#

Integrated on 2025/11/05#

Footnotes#