    001    // Copyright 2006, 2008 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
    015    package org.apache.tapestry5.internal.structure;
    016
    017    import org.apache.tapestry5.Binding;
    018    import org.apache.tapestry5.MarkupWriter;
    019    import org.apache.tapestry5.ioc.services.TypeCoercer;
    020    import org.apache.tapestry5.runtime.RenderCommand;
    021    import org.apache.tapestry5.runtime.RenderQueue;
    022
    023    public class ExpansionPageElement implements RenderCommand
    024    {
    025        private final Binding binding;
    026
    027        private final boolean invariant;
    028
    029        private final TypeCoercer coercer;
    030
    031        private boolean cached;
    032
    033        private String cachedValue;
    034
    035        public ExpansionPageElement(Binding binding, TypeCoercer coercer)
    036        {
    037            this.binding = binding;
    038            this.coercer = coercer;
    039
    040            invariant = this.binding.isInvariant();
    041        }
    042
    043        public void render(MarkupWriter writer, RenderQueue queue)
    044        {
    045            String value = cached ? cachedValue : coercer.coerce(binding.get(), String.class);
    046
    047            if (invariant && !cached)
    048            {
    049                cachedValue = value;
    050                cached = true;
    051            }
    052
    053            writer.write(value);
    054        }
    055
    056        @Override
    057        public String toString()
    058        {
    059            return String.format("Expansion[%s]", binding.toString());
    060        }
    061    }