    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}