src/main/java/rx/Notification.java
/**
* Copyright 2014 Netflix, Inc.
*
* 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 rx;
/**
* An object representing a notification sent to an {@link Observable}.
* @param <T> the actual value type held by the Notification
*/
public final class Notification<T> {
private final Kind kind;
private final Throwable throwable;
private final T value;
private static final Notification<Void> ON_COMPLETED = new Notification<Void>(Kind.OnCompleted, null, null);
/**
* Creates and returns a {@code Notification} of variety {@code Kind.OnNext}, and assigns it a value.
*
* @param <T> the actual value type held by the Notification
* @param t
* the item to assign to the notification as its value
* @return an {@code OnNext} variety of {@code Notification}
*/
public static <T> Notification<T> createOnNext(T t) {
return new Notification<T>(Kind.OnNext, t, null);
}
/**
* Creates and returns a {@code Notification} of variety {@code Kind.OnError}, and assigns it an exception.
*
* @param <T> the actual value type held by the Notification
* @param e
* the exception to assign to the notification
* @return an {@code OnError} variety of {@code Notification}
*/
public static <T> Notification<T> createOnError(Throwable e) {
return new Notification<T>(Kind.OnError, null, e);
}
/**
* Creates and returns a {@code Notification} of variety {@code Kind.OnCompleted}.
*
* @param <T> the actual value type held by the Notification
* @return an {@code OnCompleted} variety of {@code Notification}
*/
@SuppressWarnings("unchecked")
public static <T> Notification<T> createOnCompleted() {
return (Notification<T>) ON_COMPLETED;
}
/**
* Creates and returns a {@code Notification} of variety {@code Kind.OnCompleted}.
*
* @param <T> the actual value type held by the Notification
* @param type the type token to help with type inference of {@code <T>}
* @deprecated this method does the same as {@link #createOnCompleted()} and does not use the passed in type hence it's useless.
* @return an {@code OnCompleted} variety of {@code Notification}
*/
@Deprecated
@SuppressWarnings("unchecked")
public static <T> Notification<T> createOnCompleted(Class<T> type) {
return (Notification<T>) ON_COMPLETED;
}
private Notification(Kind kind, T value, Throwable e) {
this.value = value;
this.throwable = e;
this.kind = kind;
}
/**
* Retrieves the exception associated with this (onError) notification.
*
* @return the Throwable associated with this (onError) notification
*/
public Throwable getThrowable() {
return throwable;
}
/**
* Retrieves the item associated with this (onNext) notification.
*
* @return the item associated with this (onNext) notification
*/
public T getValue() {
return value;
}
/**
* Indicates whether this notification has an item associated with it.
*
* @return a boolean indicating whether or not this notification has an item associated with it
*/
public boolean hasValue() {
return isOnNext() && value != null;
// isn't "null" a valid item?
}
/**
* Indicates whether this notification has an exception associated with it.
*
* @return a boolean indicating whether this notification has an exception associated with it
*/
public boolean hasThrowable() {
return isOnError() && throwable != null;
}
/**
* Retrieves the kind of this notification: {@code OnNext}, {@code OnError}, or {@code OnCompleted}
*
* @return the kind of the notification: {@code OnNext}, {@code OnError}, or {@code OnCompleted}
*/
public Kind getKind() {
return kind;
}
/**
* Indicates whether this notification represents an {@code onError} event.
*
* @return a boolean indicating whether this notification represents an {@code onError} event
*/
public boolean isOnError() {
return getKind() == Kind.OnError;
}
/**
* Indicates whether this notification represents an {@code onCompleted} event.
*
* @return a boolean indicating whether this notification represents an {@code onCompleted} event
*/
public boolean isOnCompleted() {
return getKind() == Kind.OnCompleted;
}
/**
* Indicates whether this notification represents an {@code onNext} event.
*
* @return a boolean indicating whether this notification represents an {@code onNext} event
*/
public boolean isOnNext() {
return getKind() == Kind.OnNext;
}
/**
* Forwards this notification on to a specified {@link Observer}.
* @param observer the target observer to call onXXX methods on based on the kind of this Notification instance
*/
public void accept(Observer<? super T> observer) {
if (kind == Kind.OnNext) {
observer.onNext(getValue());
} else if (kind == Kind.OnCompleted) {
observer.onCompleted();
} else {
observer.onError(getThrowable());
}
}
/**
* Specifies the kind of the notification: an element, an error or a completion notification.
*/
public enum Kind {
OnNext, OnError, OnCompleted
}
@Override
public String toString() {
StringBuilder str = new StringBuilder(64).append('[').append(super.toString())
.append(' ').append(getKind());
if (hasValue()) {
str.append(' ').append(getValue());
}
if (hasThrowable()) {
str.append(' ').append(getThrowable().getMessage());
}
str.append(']');
return str.toString();
}
@Override
public int hashCode() {
int hash = getKind().hashCode();
if (hasValue()) {
hash = hash * 31 + getValue().hashCode();
}
if (hasThrowable()) {
hash = hash * 31 + getThrowable().hashCode();
}
return hash;
}
@Override
public boolean equals(Object obj) {
if (obj == null) {
return false;
}
if (this == obj) {
return true;
}
if (obj.getClass() != getClass()) {
return false;
}
Notification<?> notification = (Notification<?>) obj;
return notification.getKind() == getKind() && (value == notification.value || (value != null && value.equals(notification.value))) && (throwable == notification.throwable || (throwable != null && throwable.equals(notification.throwable)));
}
}