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
015package org.apache.tapestry5.internal.structure;
016
017import org.apache.tapestry5.Binding;
018import org.apache.tapestry5.MarkupWriter;
019import org.apache.tapestry5.commons.services.TypeCoercer;
020import org.apache.tapestry5.runtime.RenderCommand;
021import org.apache.tapestry5.runtime.RenderQueue;
022
023public 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}