# Exceptions - `HTTPException` and `WebSocketException`

These are the exceptions that you can raise to show errors to the client.

When you raise an exception, as would happen with normal Python, the rest of the execution is aborted. This way you can raise these exceptions from anywhere in the code to abort a request and show the error to the client.

You can use:

* `HTTPException`
* `WebSocketException`

  final Collection<? extends Throwable> exceptions;

  private ClusterException(Collection<? extends Throwable> exceptions) {
    super(
        exceptions.size() + " exceptions were thrown. The first exception is listed as a cause.",
        exceptions.iterator().next());
    ArrayList<? extends Throwable> temp = new ArrayList<>(exceptions);
    this.exceptions = Collections.unmodifiableCollection(temp);
  }

    // Exceptions
    // ------------------------------------------------------------------------

    public boolean hasExceptions() {
        return exceptions != null && !exceptions.isEmpty();
    }

    public List<Exception> getExceptions() {
        return exceptions == null ? Collections.emptyList() : Collections.unmodifiableList(exceptions);
    }

  final Collection<? extends Throwable> exceptions;

  private ClusterException(Collection<? extends Throwable> exceptions) {
    super(
        exceptions.size() + " exceptions were thrown. The first exception is listed as a cause.",
        exceptions.iterator().next());
    ArrayList<? extends Throwable> temp = new ArrayList<>(exceptions);
    this.exceptions = Collections.unmodifiableCollection(temp);
  }

/**
 * Base class for all maven exceptions carrying {@link BuilderProblem}s.
 *
 * @since 4.0.0
 */
@Experimental
public abstract class MavenBuilderException extends MavenException {

    /**
     * The collection of problems associated with this exception.
     */
    private final ProblemCollector<BuilderProblem> problems;

    /**
     * Constructs a new exception with the specified message and cause.

                        BufferCache.releaseBuffer(buffer);
                        successCount.incrementAndGet();
                    }
                } catch (Exception e) {
                    synchronized (exceptions) {
                        exceptions.add(e);
                    }
                } finally {
                    endLatch.countDown();
                }
            });
        }

      // the operation would be a no-op, so exceptions are allowed but not required
    }
    expectUnchanged();
  }

  @MapFeature.Require(absent = SUPPORTS_PUT)
  public void testReplaceEntry_unsupportedAbsentKey() {
    try {
      getMap().replace(k3(), v3(), v4());
    } catch (UnsupportedOperationException tolerated) {
      // the operation would be a no-op, so exceptions are allowed but not required
    }

      // the operation would be a no-op, so exceptions are allowed but not required
    }
    expectUnchanged();
  }

  @MapFeature.Require(absent = SUPPORTS_PUT)
  public void testReplaceEntry_unsupportedAbsentKey() {
    try {
      getMap().replace(k3(), v3(), v4());
    } catch (UnsupportedOperationException tolerated) {
      // the operation would be a no-op, so exceptions are allowed but not required
    }

     * exception, and wrongly believes that its exception is new (leading it to logging it when it
     * shouldn't)
     *
     * Our solution is for threads to CAS seenExceptionsField from null to a Set populated with _the
     * initial exception_, no matter which thread does the work. This ensures that
     * seenExceptionsField always contains not just the current thread's exception but also the
     * initial thread's.
     */

        }
      }
    }
    if (!suppressThrows && (exceptions.size() > 0)) {
      throw ClusterException.create(exceptions);
    }
  }