001// Copyright 2010, 2011, 2012 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.internal.transform;
016
017import org.apache.tapestry5.Binding;
018import org.apache.tapestry5.annotations.Parameter;
019import org.apache.tapestry5.internal.InternalComponentResources;
020import org.apache.tapestry5.ioc.services.TypeCoercer;
021import org.apache.tapestry5.plastic.FieldConduit;
022
023/**
024 * A facade around {@link Binding} and {@link InternalComponentResources} that is used to instrument
025 * fields with the {@link Parameter} annotation. Extends {@link FieldConduit} so that
026 * the get() method implicitly coerces the value to the field's type.
027 * <p/>
028 * {@link #get(Object, org.apache.tapestry5.plastic.InstanceContext)} will read from the underlying {@link Binding} and used the {@link TypeCoercer} coerce the value to the
029 * parameter field's type. get() also includes a null value check (as per {@link Parameter#allowNull()}.
030 * <p/>
031 * {@link #set(Object, org.apache.tapestry5.plastic.InstanceContext, Object)} pushes the value into the binding.
032 *
033 * @since 5.2.0
034 */
035public interface ParameterConduit extends FieldConduit<Object>
036{
037    /**
038     * Determines if the parameter is actually bound.
039     *
040     * @return true if bound
041     */
042    boolean isBound();
043
044    /**
045     * Resets the conduit, clearing any <em>temporarily</em> cached data (from a non-invariant {@link Binding}).
046     */
047    void reset();
048}