| // Copyright 2010 The Apache Software Foundation |
| // |
| // 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 org.apache.tapestry5.ioc.services; |
| |
| import java.util.Objects; |
| import java.util.function.Consumer; |
| import java.util.function.Function; |
| import java.util.function.Supplier; |
| |
| /** |
| * Provides access to per-thread (and, by extension, per-request) data, managed by the {@link PerthreadManager}. |
| * A PerThreadValue stores a particular type of information. |
| * |
| * @see org.apache.tapestry5.ioc.services.PerthreadManager#createValue() |
| * @since 5.2.0 |
| */ |
| public interface PerThreadValue<T> |
| { |
| /** |
| * Is a value stored (even null)? |
| */ |
| boolean exists(); |
| |
| /** |
| * Reads the current per-thread value, or returns null if no value has been stored. |
| */ |
| T get(); |
| |
| /** |
| * Gets the current per-thread value if it exists (even if null), or the defaultValue |
| * if no value has been stored. |
| */ |
| T get(T defaultValue); |
| |
| /** |
| * Sets the current per-thread value, then returns that value. |
| */ |
| T set(T newValue); |
| |
| /** |
| * If no value is currently stored (checked by {@link #exists()}), the value |
| * provided by the supplier function is set and return. |
| * Otherwise, the current value is returned. |
| * |
| * @param fn the value supplier function |
| * @return The current (existing or computed) value |
| * @throws NullPointerException if the supplier function is null |
| * @since 5.8.3 |
| */ |
| default T computeIfAbsent(Supplier<? extends T> fn) { |
| Objects.requireNonNull(fn); |
| if (exists()) { |
| return get(); |
| } |
| |
| T newValue = fn.get(); |
| set(newValue); |
| |
| return newValue; |
| } |
| |
| /** |
| * If a value is currently stored (checked by {@link #exists()}), this value |
| * is used to compute a new one with the given mapping function. |
| * Otherwise, null is returned. |
| * |
| * @param fn the mapping function to compute the new value |
| * @return The new computed value, or null if none was present |
| * @throws NullPointerException if the mapping function is null |
| * @since 5.8.3 |
| */ |
| default T computeIfPresent(Function<? super T, ? extends T> fn) { |
| Objects.requireNonNull(fn); |
| if (!exists()) { |
| return null; |
| } |
| |
| T newValue = fn.apply(get()); |
| set(newValue); |
| |
| return newValue; |
| } |
| |
| /** |
| * Computes a new value with the help of the current one, which is returned. |
| * |
| * @param fn the mapping function to compute the new value |
| * @return The new computed value |
| * @throws NullPointerException if the mapping function is null |
| * @since 5.8.3 |
| */ |
| default T compute(Function<? super T, ? extends T> fn) { |
| Objects.requireNonNull(fn); |
| |
| T newValue = fn.apply(get()); |
| set(newValue); |
| |
| return newValue; |
| } |
| |
| /** |
| * If a value is set, performs the given action with it, otherwise it |
| * does nothing. |
| * |
| * @param action performed action if a value is set |
| * @throws NullPointerException if the action is null |
| * @since 5.8.3 |
| */ |
| default void ifSet(Consumer<? super T> action) { |
| Objects.requireNonNull(action); |
| |
| if (!exists()) { |
| return; |
| } |
| |
| action.accept(get()); |
| } |
| } |