tapestry/tapestry-framework/src/java/org/apache/tapestry/pageload/EstablishDefaultParameterValuesVisitor.java

// Copyright 2004, 2005 The Apache Software Foundation
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package org.apache.tapestry.pageload;

import org.apache.hivemind.ApplicationRuntimeException;
import org.apache.tapestry.IBinding;
import org.apache.tapestry.IComponent;
import org.apache.tapestry.binding.BindingConstants;
import org.apache.tapestry.binding.BindingSource;
import org.apache.tapestry.spec.IComponentSpecification;
import org.apache.tapestry.spec.IParameterSpecification;

import java.util.Iterator;

/**
 * For all parameters in the examined component that have default values, but
 * are not bound, automatically add an ExpressionBinding with the default value.
 * 
 * @author mindbridge
 * @since 3.0
 */
public class EstablishDefaultParameterValuesVisitor implements IComponentVisitor
{

    /** @since 4.0 */
    private BindingSource _bindingSource;

    /**
     * @see org.apache.tapestry.pageload.IComponentVisitor#visitComponent(org.apache.tapestry.IComponent)
     */
    public void visitComponent(IComponent component)
    {
        IComponentSpecification spec = component.getSpecification();

        Iterator i = spec.getParameterNames().iterator();

        while(i.hasNext())
        {
            String name = (String) i.next();
            IParameterSpecification parameterSpec = spec.getParameter(name);

            // Skip aliases

            if (!name.equals(parameterSpec.getParameterName())) continue;

            String defaultValue = parameterSpec.getDefaultValue();
            if (defaultValue == null) continue;

            // the parameter has a default value, so it must not be required
            if (parameterSpec.isRequired())
                throw new ApplicationRuntimeException(PageloadMessages
                        .parameterMustHaveNoDefaultValue(component, name),
                        component, parameterSpec.getLocation(), null);

            // if there is no binding for this parameter, bind it to the default
            // value.
            // In 3.0, default-value was always an OGNL expression, but now its
            // a binding reference.

            if (component.getBinding(name) == null)
            {
                String description = PageloadMessages
                        .defaultParameterName(name);

                IBinding binding = _bindingSource.createBinding(component,
                        description, defaultValue,
                        BindingConstants.OGNL_PREFIX, parameterSpec
                                .getLocation());

                component.setBinding(name, binding);
            }
        }
    }

    /** @since 4.0 */

    public void setBindingSource(BindingSource bindingSource)
    {
        _bindingSource = bindingSource;
    }
}