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30 day Evaluation Version distributed via the Maven Jar Repository. Clover is not free. You have 30 days to evaluate it. Please visit http://www.thecortex.net/clover to obtain a licensed version of Clover | |||||||||||||||||||
Source file | Conditionals | Statements | Methods | TOTAL | |||||||||||||||
ExpressionBinding.java | 83.3% | 100% | 100% | 97.9% |
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// Copyright 2004, 2005 The Apache Software Foundation
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package org.apache.tapestry.binding;
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import org.apache.hivemind.Location;
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import org.apache.tapestry.BindingException;
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import org.apache.tapestry.IComponent;
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import org.apache.tapestry.coerce.ValueConverter;
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import org.apache.tapestry.services.ExpressionCache;
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import org.apache.tapestry.services.ExpressionEvaluator;
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/**
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* Implements a dynamic binding, based on evaluating an expression using an expression language.
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* Tapestry's default expression language is the <a href="http://www.ognl.org/">Object Graph
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* Navigation Language </a>.
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*
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* @see org.apache.tapestry.services.ExpressionEvaluator
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* @author Howard Lewis Ship
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* @since 2.2
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*/
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public class ExpressionBinding extends AbstractBinding |
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{ |
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/**
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* The root object against which the nested property name is evaluated.
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*/
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private final IComponent _root;
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/**
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* The OGNL expression, as a string.
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*/
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private String _expression;
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/**
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* If true, then the binding is invariant.
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*/
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private boolean _invariant = false; |
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/**
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* Parsed OGNL expression.
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*/
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private Object _parsedExpression;
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/**
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* Flag set to true once the binding has initialized.
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*/
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private boolean _initialized; |
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/**
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* @since 4.0
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*/
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private ExpressionEvaluator _evaluator;
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/** @since 4.0 */
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private ExpressionCache _cache;
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/**
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* Creates a {@link ExpressionBinding}from the root object and an OGNL expression.
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*/
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public ExpressionBinding(String description, Location location, ValueConverter valueConverter,
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IComponent root, String expression, ExpressionEvaluator evaluator, |
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ExpressionCache cache) |
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{ |
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super(description, valueConverter, location);
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_root = root; |
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_expression = expression; |
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_evaluator = evaluator; |
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_cache = cache; |
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} |
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/**
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* Gets the value of the property path, with the assistance of the {@link ExpressionEvaluator}.
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*
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* @throws BindingException
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* if an exception is thrown accessing the property.
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*/
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public Object getObject()
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{ |
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initialize(); |
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return resolveExpression();
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} |
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private Object resolveExpression()
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{ |
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try
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{ |
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return _evaluator.readCompiled(_root, _parsedExpression);
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} |
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catch (Throwable t)
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{ |
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throw new BindingException(t.getMessage(), this, t); |
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} |
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} |
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/**
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* Returns true if the binding is expected to always return the same value.
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*/
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public boolean isInvariant() |
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{ |
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initialize(); |
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return _invariant;
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} |
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/**
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* Sets up the helper object, but also optimizes the property path and determines if the binding
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* is invarant.
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*/
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private void initialize() |
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{ |
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if (_initialized)
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return;
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_initialized = true;
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try
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{ |
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_parsedExpression = _cache.getCompiledExpression(_expression); |
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_invariant = _evaluator.isConstant(_expression); |
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} |
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catch (Exception ex)
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{ |
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throw new BindingException(ex.getMessage(), this, ex); |
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} |
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} |
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/**
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* Updates the property for the binding to the given value.
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*
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* @throws BindingException
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* if the property can't be updated (typically due to an security problem, or a
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* missing mutator method).
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* @throws ReadOnlyBindingException
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* if the binding is invariant.
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*/
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public void setObject(Object value) |
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{ |
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initialize(); |
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if (_invariant)
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throw createReadOnlyBindingException(this); |
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try
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{ |
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_evaluator.writeCompiled(_root, _parsedExpression, value); |
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} |
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catch (Throwable ex)
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{ |
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throw new BindingException(ex.getMessage(), this, ex); |
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} |
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} |
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/**
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* Returns the a String representing the property path. This includes the
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* {@link IComponent#getExtendedId() extended id}of the root component and the property path
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* ... once the binding is used, these may change due to optimization of the property path.
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*/
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public String toString()
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{ |
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StringBuffer buffer = new StringBuffer();
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buffer.append("ExpressionBinding[");
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buffer.append(_root.getExtendedId()); |
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if (_expression != null) |
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{ |
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buffer.append(' '); |
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buffer.append(_expression); |
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} |
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buffer.append(']'); |
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return buffer.toString();
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} |
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/** @since 4.0 */
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public Object getComponent()
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{ |
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return _root;
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} |
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} |
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