| // Copyright 2006-2014 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.services; |
| |
| import java.util.NoSuchElementException; |
| |
| /** |
| * Provides access to environment objects, which are almost always provided to enclosed components by enclosing |
| * components. Environmental services are a form of very late binding. |
| * <p/> |
| * The Environment acts like a collection of stacks. Each stack contains environmental objects of a given type. Most |
| * often, a stack has zero or one elements, but on occasion, a particular component will push an override onto the stack |
| * for the benefit of the components it encloses. |
| * |
| * @see org.apache.tapestry5.annotations.Environmental |
| * @see org.apache.tapestry5.services.EnvironmentalShadowBuilder |
| */ |
| public interface Environment |
| { |
| /** |
| * Peeks at the current top of the indicated stack. |
| * |
| * @param <T> the type of environmental object |
| * @param type class used to select the object |
| * @return the current object of that type, or null if no service of that type has been added |
| */ |
| <T> T peek(Class<T> type); |
| |
| /** |
| * Peeks at the current top of the indicated stack (which must have a non-null value). |
| * |
| * @param <T> the type of environmental object |
| * @param type class used to select the object |
| * @return the current object of the specified type |
| * @throws RuntimeException if no service of that type has been added |
| */ |
| <T> T peekRequired(Class<T> type); |
| |
| /** |
| * Removes and returns the top environmental object of the selected type. |
| * |
| * @param <T> the type of environmental object |
| * @param type class used to select the object |
| * @return the object just removed |
| * @throws NoSuchElementException if the environmental stack (for the specified type) is empty |
| */ |
| <T> T pop(Class<T> type); |
| |
| /** |
| * Pushes a new service onto the stack. The old service at the top of the stack is returned (it may be null). |
| * |
| * @param <T> the type of environmental object |
| * @param type class used to select the object |
| * @param instance the service object |
| * @return the previous top service |
| */ |
| <T> T push(Class<T> type, T instance); |
| |
| /** |
| * Hides all current environment values, making the Environment object appear empty, until |
| * a call to {@link #decloak()}} restores the original state. |
| * |
| * @since 5.3 |
| * @deprecated Deprecated in 5.4 with no replacement; not longer used by Tapestry. |
| * @see org.apache.tapestry5.TapestryConstants#RESPONSE_RENDERER |
| */ |
| void cloak(); |
| |
| /** |
| * Restores state previously hidden by {@link #cloak()}}. |
| * |
| * @since 5.3 |
| * @deprecated Deprecated in 5.4 with no replacement; not longer used by Tapestry. |
| * @see org.apache.tapestry5.TapestryConstants#RESPONSE_RENDERER |
| */ |
| void decloak(); |
| } |