| // Copyright 2004 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 ognl.Ognl; |
| |
| import org.apache.tapestry.ApplicationRuntimeException; |
| import org.apache.tapestry.IComponent; |
| import org.apache.tapestry.ILocation; |
| import org.apache.tapestry.IResourceResolver; |
| import org.apache.tapestry.Tapestry; |
| import org.apache.tapestry.event.PageDetachListener; |
| import org.apache.tapestry.event.PageEvent; |
| import org.apache.tapestry.util.prop.OgnlUtils; |
| |
| /** |
| * Given a component, a property and a value, this object will |
| * reset the property to the value whenever the page |
| * (containing the component) is detached. This is related |
| * to support for {@link org.apache.tapestry.spec.IPropertySpecification}s. |
| * |
| * @author Howard Lewis Ship |
| * @version $Id$ |
| * @since 3.0 |
| **/ |
| |
| public class PropertyInitializer implements PageDetachListener |
| { |
| private IResourceResolver _resolver; |
| private IComponent _component; |
| private String _propertyName; |
| private String _expression; |
| private boolean _invariant; |
| private Object _value; |
| private ILocation _location; |
| |
| public PropertyInitializer( |
| IResourceResolver resolver, |
| IComponent component, |
| String propertyName, |
| String expression, |
| ILocation location) |
| { |
| _resolver = resolver; |
| _component = component; |
| _propertyName = propertyName; |
| _expression = expression; |
| _location = location; |
| |
| prepareInvariant(); |
| } |
| |
| public void prepareInvariant() |
| { |
| _invariant = false; |
| |
| try |
| { |
| // If no initial value expression is provided, then read the current |
| // property of the expression. This may be null, or may be |
| // a value set in finishLoad() (via an abstract accessor). |
| |
| if (Tapestry.isBlank(_expression)) |
| { |
| _invariant = true; |
| _value = OgnlUtils.get(_propertyName, _resolver, _component); |
| } |
| else |
| if (Ognl.isConstant(_expression, Ognl.createDefaultContext(_component, _resolver))) |
| { |
| // If the expression is a constant, evaluate it and remember the value |
| _invariant = true; |
| _value = OgnlUtils.get(_expression, _resolver, _component); |
| } |
| } |
| catch (Exception ex) |
| { |
| throw new ApplicationRuntimeException( |
| Tapestry.format( |
| "PageLoader.unable-to-initialize-property", |
| _propertyName, |
| _component, |
| ex.getMessage()), |
| _location, |
| ex); |
| } |
| } |
| |
| public void pageDetached(PageEvent event) |
| { |
| try |
| { |
| if (_invariant) |
| OgnlUtils.set(_propertyName, _resolver, _component, _value); |
| else |
| { |
| Object value = OgnlUtils.get(_expression, _resolver, _component); |
| OgnlUtils.set(_propertyName, _resolver, _component, value); |
| } |
| } |
| catch (Exception ex) |
| { |
| throw new ApplicationRuntimeException( |
| Tapestry.format( |
| "PageLoader.unable-to-initialize-property", |
| _propertyName, |
| _component, |
| ex.getMessage()), |
| _location, |
| ex); |
| } |
| } |
| |
| } |