chore(bqjdbc): enhance exception messages to include chained exception message

java-bigquery/google-cloud-bigquery-jdbc/src/main/java/com/google/cloud/bigquery/exception/BigQueryConversionException.java

@@ -27,7 +27,7 @@ public class BigQueryConversionException extends SQLException {
       new BigQueryJdbcCustomLogger(BigQueryConversionException.class.getName());
 
   public BigQueryConversionException(String message, Throwable cause) {
-    super(message, cause);
-    LOG.severe(message, this);
+    super(BigQueryJdbcExceptionUtils.formatMessage(message, cause), cause);
+    LOG.severe(this.getMessage(), this);
   }
 }

java-bigquery/google-cloud-bigquery-jdbc/src/main/java/com/google/cloud/bigquery/exception/BigQueryJdbcCoercionException.java

@@ -34,7 +34,7 @@ public class BigQueryJdbcCoercionException extends RuntimeException {
    * @param cause the actual cause which was thrown while performing the coercion.
    */
   public BigQueryJdbcCoercionException(Exception cause) {
-    super("Coercion error", cause);
-    LOG.severe("Coercion error", this);
+    super(BigQueryJdbcExceptionUtils.formatMessage("Coercion error", cause), cause);
+    LOG.severe(this.getMessage(), this);
   }
 }

java-bigquery/google-cloud-bigquery-jdbc/src/main/java/com/google/cloud/bigquery/exception/BigQueryJdbcException.java

@@ -52,9 +52,9 @@ public BigQueryJdbcException(InterruptedException ex) {
    * @param ex The BigQueryException to be thrown.
    */
   public BigQueryJdbcException(String message, BigQueryException ex) {
-    super(message, ex);
+    super(BigQueryJdbcExceptionUtils.formatMessage(message, ex), ex);
     this.bigQueryException = ex;
-    LOG.severe(ex.getMessage(), this);
+    LOG.severe(this.getMessage(), this);
   }
 
   /**
@@ -64,8 +64,8 @@ public BigQueryJdbcException(String message, BigQueryException ex) {
    * @param cause Throwable that is being converted.
    */
   public BigQueryJdbcException(String message, Throwable cause) {
-    super(message, cause);
-    LOG.severe(message, this);
+    super(BigQueryJdbcExceptionUtils.formatMessage(message, cause), cause);
+    LOG.severe(this.getMessage(), this);
   }
 
   /**

java-bigquery/google-cloud-bigquery-jdbc/src/main/java/com/google/cloud/bigquery/exception/BigQueryJdbcExceptionUtils.java

@@ -0,0 +1,40 @@
+/*
+ * Copyright 2026 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.cloud.bigquery.exception;
+
+/** Utility class for JDBC exceptions. */
+final class BigQueryJdbcExceptionUtils {
+
+  private BigQueryJdbcExceptionUtils() {
+    // Utility class, prevent instantiation
+  }
+
+  /**
+   * Formats the exception message by appending the cause's message (or toString if null) on a
+   * newline.
+   *
+   * @param message The custom detail message.
+   * @param cause The underlying cause of the exception.
+   * @return The formatted message.
+   */
+  public static String formatMessage(String message, Throwable cause) {
+    return message
+        + (cause != null
+            ? "\n" + (cause.getMessage() != null ? cause.getMessage() : cause.toString())
+            : "");
+  }
+}

java-bigquery/google-cloud-bigquery-jdbc/src/main/java/com/google/cloud/bigquery/exception/BigQueryJdbcRuntimeException.java

@@ -50,12 +50,12 @@ public BigQueryJdbcRuntimeException(Throwable ex) {
    * @param ex Throwable to be thrown.
    */
   public BigQueryJdbcRuntimeException(String message, InterruptedException ex) {
-    super(message, ex);
-    LOG.severe(message, this);
+    super(BigQueryJdbcExceptionUtils.formatMessage(message, ex), ex);
+    LOG.severe(this.getMessage(), this);
   }
 
   public BigQueryJdbcRuntimeException(String message, Throwable ex) {
-    super(message, ex);
-    LOG.severe(message, this);
+    super(BigQueryJdbcExceptionUtils.formatMessage(message, ex), ex);
+    LOG.severe(this.getMessage(), this);
   }
 }

java-bigquery/google-cloud-bigquery-jdbc/src/main/java/com/google/cloud/bigquery/exception/BigQueryJdbcSqlSyntaxErrorException.java

@@ -40,7 +40,7 @@ public BigQueryJdbcSqlSyntaxErrorException(BigQueryException ex) {
   }
 
   public BigQueryJdbcSqlSyntaxErrorException(String message, BigQueryException ex) {
-    super(message, ex);
-    LOG.severe(message, this);
+    super(BigQueryJdbcExceptionUtils.formatMessage(message, ex), ex);
+    LOG.severe(this.getMessage(), this);
   }
 }

java-bigquery/google-cloud-bigquery-jdbc/src/test/java/com/google/cloud/bigquery/exception/BigQueryJdbcExceptionTest.java

@@ -0,0 +1,78 @@
+/*
+ * Copyright 2026 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.cloud.bigquery.exception;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import com.google.cloud.bigquery.BigQueryException;
+import java.util.stream.Stream;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
+
+public class BigQueryJdbcExceptionTest {
+
+  @FunctionalInterface
+  interface ExceptionCreator {
+    Throwable create(String message, Throwable cause);
+  }
+
+  static Stream<Arguments> exceptionProvider() {
+    return Stream.of(
+        Arguments.of(
+            (ExceptionCreator)
+                (msg, cause) -> new BigQueryJdbcException(msg, (BigQueryException) cause)),
+        Arguments.of((ExceptionCreator) BigQueryJdbcException::new),
+        Arguments.of((ExceptionCreator) BigQueryJdbcRuntimeException::new),
+        Arguments.of((ExceptionCreator) BigQueryConversionException::new),
+        Arguments.of(
+            (ExceptionCreator)
+                (msg, cause) -> new BigQueryJdbcCoercionException((Exception) cause)),
+        Arguments.of(
+            (ExceptionCreator)
+                (msg, cause) ->
+                    new BigQueryJdbcSqlSyntaxErrorException(msg, (BigQueryException) cause)));
+  }
+
+  @ParameterizedTest
+  @MethodSource("exceptionProvider")
+  public void testExceptionMessageFormatting(ExceptionCreator creator) {
+    String message = "Custom error message";
+    Throwable cause = new BigQueryException(500, "Underlying error");
+
+    Throwable ex = creator.create(message, cause);
+
+    String expectedPrefix =
+        ex instanceof BigQueryJdbcCoercionException ? "Coercion error" : message;
+    String expectedMessage = expectedPrefix + "\n" + cause.getMessage();
+
+    assertEquals(expectedMessage, ex.getMessage());
+    assertEquals(cause, ex.getCause());
+  }
+
+  @Test
+  public void testException_withCauseHavingNullMessage() {
+    String message = "Custom error message";
+    Throwable cause = new RuntimeException(); // Null message
+
+    BigQueryJdbcException ex = new BigQueryJdbcException(message, cause);
+
+    String expectedMessage = message + "\n" + cause.toString();
+    assertEquals(expectedMessage, ex.getMessage());
+  }
+}

java-bigquery/google-cloud-bigquery-jdbc/src/test/java/com/google/cloud/bigquery/jdbc/BigQueryTypeCoercerTest.java

@@ -78,7 +78,7 @@ public void shouldThrowCoercionException() {
         assertThrows(
             BigQueryJdbcCoercionException.class,
             () -> bigQueryTypeCoercer.coerceTo(Integer.class, 2147483648L));
-    assertThat(exception.getMessage()).isEqualTo("Coercion error");
+    assertThat(exception.getMessage()).isEqualTo("Coercion error\ninteger overflow");
     assertThat(exception.getCause()).isInstanceOf(ArithmeticException.class);
   }