001// Copyright 2006, 2007 The Apache Software Foundation 002// 003// Licensed under the Apache License, Version 2.0 (the "License"); 004// you may not use this file except in compliance with the License. 005// You may obtain a copy of the License at 006// 007// http://www.apache.org/licenses/LICENSE-2.0 008// 009// Unless required by applicable law or agreed to in writing, software 010// distributed under the License is distributed on an "AS IS" BASIS, 011// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 012// See the License for the specific language governing permissions and 013// limitations under the License. 014 015package org.apache.tapestry5; 016 017import org.apache.tapestry5.ioc.AnnotationProvider; 018 019/** 020 * A binding is a connection between a component and its container (another component), that allows the embedded 021 * component to gain access to <em>resources</em> defined by the container. Resources can represent any kind of value 022 * that can be obtained from the parent component, but is often a JavaBean property that can be read and updated. 023 * Different implementations of Binding as used to access different kinds of resources of the container. 024 * <p/> 025 * A binding ultimately must provide access to the underlying annotations. In most cases, there are no annotations, but 026 * bindings that ultimate invoke methods or read and update fields must provide access to those annotations. 027 */ 028public interface Binding extends AnnotationProvider 029{ 030 /** 031 * Reads the current value of the property (or other resource). When reading properties of objects that are 032 * primitive types, this will return an instance of the wrapper type. In some cases, a binding is read only and this 033 * method will throw a runtime exception. 034 */ 035 Object get(); 036 037 /** 038 * Updates the current value. Most types of bindings are read-only, and this method will throw a runtime exception. 039 * It is the caller's responsibility to ensure that the value passed in is of the appropriate type. 040 * 041 * @param value 042 */ 043 void set(Object value); 044 045 /** 046 * Returns true if the value of the binding does not ever change. Components will often cache such values 047 * aggressively. 048 */ 049 boolean isInvariant(); 050 051 /** 052 * Returns the type of the binding, either the type of resource exposed by the binding, or the type of the property 053 * bound. 054 */ 055 Class getBindingType(); 056}