Sie können diese Exceptionhandler mit Ihren eigenen überschreiben.

### Überschreiben von Request-Validierungs-Exceptions { #override-request-validation-exceptions }

Wenn ein Request ungültige Daten enthält, löst **FastAPI** intern einen `RequestValidationError` aus.

Und es enthält auch einen Default-Exceptionhandler für diesen.

You can override these exception handlers with your own.

### Override request validation exceptions { #override-request-validation-exceptions }

When a request contains invalid data, **FastAPI** internally raises a `RequestValidationError`.

And it also includes a default exception handler for it.

 * guaranteed to execute. There is no guarantee, however, that listeners will be executed in the
 * order that they are added.
 *
 * <p>Exceptions thrown by a listener will be propagated up to the executor. Any exception thrown
 * during {@code Executor.execute} (e.g., a {@code RejectedExecutionException} or an exception

 * error handling, and validation in web API context.
 */
public final class WebApiUtil {

    /**
     * Request attribute key for storing web API exceptions.
     */
    private static final String WEB_API_EXCEPTION = "webApiException";

    /**
     * Private constructor to prevent instantiation.
     */
    private WebApiUtil() {
    }

    /**

   *   }
   * }
   * }
   *
   * @param closeable the {@code Closeable} object to be closed, or null, in which case this method
   *     does nothing
   * @param swallowIOException if true, don't propagate IO exceptions thrown by the {@code close}
   *     methods
   * @throws IOException if {@code swallowIOException} is false and {@code close} throws an {@code
   *     IOException}.
   */
  /*

    PLATFORM {
      @GwtIncompatible
      @J2ktIncompatible
      @Override
      // returns the types available in "normal" environments
      ImmutableMap<Class<? extends Throwable>, Predicate<Throwable>> exceptions() {
        return ImmutableMap.of(
            InvocationTargetException.class,
            e -> e instanceof InvocationTargetException,
            StackOverflowError.class,

     * Verify that all methods can be called with null buffers without
     * throwing exceptions. This test ensures robustness of the implementation.
     */
    @Test
    void methodsHandleNullBuffersGracefully() {
        // Arrange
        TransWaitNamedPipeResponse resp = new TransWaitNamedPipeResponse();
        // Act & Assert - no exceptions should be thrown
        assertDoesNotThrow(() -> resp.writeSetupWireFormat(null, 0));

        assertNull(queryParseException.getCause());
        // getMessage() may return null when constructed with null
        // This is expected behavior for exceptions with null cause
    }

    @Test
    public void test_nestedCause() {
        // Test with nested exceptions
        RuntimeException rootCause = new RuntimeException("Root cause");
        ParseException parseException = new ParseException("Parse error");

    ).containsExactly(
      "--> GET http://google.com/robots.txt",
      "<-- HTTP FAILED: java.net.UnknownHostException: shortcircuit. ${request.url} (ms)",
    )
    // We should consider if these logs should retain Exceptions
    assertThat(logs.last().throwable).isNull()
  }

  @Test
  fun testLoggingEventListener() {
    val client = clientBuilder.eventListenerFactory(LoggingEventListener.Factory()).build()

    try {

But it's there for you if you need it. 🤓

///

{* ../../docs_src/dependencies/tutorial008b_an_py310.py hl[18:22,31] *}