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    }