Unwrap completion exception for legacy async handling

ibauersachs · bhaveshthakker · ibauersachs · commit cd0bbdf991b3 · 2025-06-28T18:36:58.000+02:00
Closes #383 Co-authored-by: bhaveshthakker <bhaveshthakker111@gmail.com>
diff --git a/src/main/java/org/xbill/DNS/Resolver.java b/src/main/java/org/xbill/DNS/Resolver.java
@@ -9,6 +9,7 @@
 import java.util.Collections;
 import java.util.List;
 import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.CompletionException;
 import java.util.concurrent.CompletionStage;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.Executor;
@@ -239,11 +240,16 @@ default Object sendAsync(Message query, ResolverListener listener) {
         (result, throwable) -> {
           if (throwable != null) {
             Exception exception;
+            if (throwable instanceof CompletionException && throwable.getCause() != null) {
+              throwable = throwable.getCause();
+            }
+
             if (throwable instanceof Exception) {
               exception = (Exception) throwable;
             } else {
               exception = new Exception(throwable);
             }
+
             listener.handleException(id, exception);
             return null;
           }
diff --git a/src/test/java/org/xbill/DNS/ResolverTest.java b/src/test/java/org/xbill/DNS/ResolverTest.java
@@ -0,0 +1,47 @@
+// SPDX-License-Identifier: BSD-3-Clause
+package org.xbill.DNS;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.fail;
+
+import java.net.UnknownHostException;
+import java.time.Duration;
+import java.util.concurrent.CompletionException;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
+import org.junit.jupiter.api.Test;
+
+class ResolverTest {
+  @Test
+  @SuppressWarnings("deprecation")
+  void resolverListenerExceptionUnwrap() throws InterruptedException, UnknownHostException {
+    // 1. Point to a blackhole address from RFC 5737 TEST-NET-1 to ensure a timeout
+    SimpleResolver resolver = new SimpleResolver("192.0.2.1");
+    resolver.setTimeout(Duration.ofSeconds(2));
+
+    Message query =
+        Message.newQuery(
+            Record.newRecord(Name.fromConstantString("example.com."), Type.A, DClass.IN));
+    CountDownLatch latch = new CountDownLatch(1);
+
+    // 2. Use the async method with a listener
+    resolver.sendAsync(
+        query,
+        new ResolverListener() {
+          @Override
+          public void receiveMessage(Object id, Message m) {
+            fail("Received message (should not happen)");
+            latch.countDown();
+          }
+
+          @Override
+          public void handleException(Object id, Exception ex) {
+            // 3. Observe the exception type
+            assertThat(ex).isNotInstanceOf(CompletionException.class);
+            latch.countDown();
+          }
+        });
+
+    latch.await(5, TimeUnit.SECONDS);
+  }
+}
