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package org.codehaus.plexus.interpolation;

/*
 * Copyright 2001-2008 Codehaus 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.
 */

/**
 * {@link ValueSource} abstract implementation that wraps another value source.
 * When an expression is resolved, this wrapped source is first used to retrieve
 * the expression's actual value; then, the last expression processed by this
 * source is retrieved, and the two are passed into the abstract method
 * {@link AbstractFunctionValueSourceWrapper#executeFunction(String, Object)}
 * together. The result of this is returned as the resolved value for the second
 * expression.
 * 
* This allows the first expression to be a function name that modifies the * value of the second expression, which is resolved from the wrapped value * source. * @version $Id$ */ public abstract class AbstractFunctionValueSourceWrapper implements ValueSource { private final ValueSource valueSource; /** * Construct a new function value source instance, using the supplied {@link ValueSource} * to retrieve the input values for the function(s) this class implements. * * @param valueSource The value source to wrap */ protected AbstractFunctionValueSourceWrapper( ValueSource valueSource ) { this.valueSource = valueSource; } /** *
    *
  1. Resolve the current expression using the embedded {@link ValueSource}
  2. *
  3. Retrieve the last expression processed by this value source
  4. *
  5. Pass the last expression (which should be the function name), along * with the value for the current expression, into the * executeFunction(..) method
  6. *
  7. Return the result of the executeFunction(..) as the resolved value * for the current expression.
  8. *
*/ public Object getValue( String expression ) { Object value = valueSource.getValue( expression ); String expr = expression; if ( valueSource instanceof QueryEnabledValueSource ) { expr = ((QueryEnabledValueSource) valueSource).getLastExpression(); } return executeFunction( expr, value ); } /** * Retrieve the embedded value source. */ protected ValueSource getValueSource() { return valueSource; } /** * Execute the function referenced in the last-processed expression using the * value resolved from the current expression (using the embedded {@link ValueSource}). * * @param expression The last expression to be processed by this value source. * @param value The value for the current expression, resolved by the embedded {@link ValueSource} * @return The result of modifying the current expression's value using the function named by the last expression. */ protected abstract Object executeFunction( String expression, Object value ); }




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