1 package org.codehaus.plexus.interpolation; 2 3 /* 4 * Copyright 2001-2008 Codehaus Foundation. 5 * 6 * Licensed under the Apache License, Version 2.0 (the "License"); 7 * you may not use this file except in compliance with the License. 8 * You may obtain a copy of the License at 9 * 10 * http://www.apache.org/licenses/LICENSE-2.0 11 * 12 * Unless required by applicable law or agreed to in writing, software 13 * distributed under the License is distributed on an "AS IS" BASIS, 14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 15 * See the License for the specific language governing permissions and 16 * limitations under the License. 17 */ 18 19 /** 20 * {@link ValueSource} abstract implementation that wraps another value source. 21 * When an expression is resolved, this wrapped source is first used to retrieve 22 * the expression's actual value; then, the last expression processed by this 23 * source is retrieved, and the two are passed into the abstract method 24 * {@link AbstractFunctionValueSourceWrapper#executeFunction(String, Object)} 25 * together. The result of this is returned as the resolved value for the second 26 * expression. 27 * <p>This allows the first expression to be a function name that modifies the 28 * value of the second expression, which is resolved from the wrapped value 29 * source.</p> 30 */ 31 public abstract class AbstractFunctionValueSourceWrapper implements ValueSource { 32 33 private final ValueSource valueSource; 34 35 /** 36 * Construct a new function value source instance, using the supplied {@link ValueSource} 37 * to retrieve the input values for the function(s) this class implements. 38 * 39 * @param valueSource The value source to wrap 40 */ 41 protected AbstractFunctionValueSourceWrapper(ValueSource valueSource) { 42 this.valueSource = valueSource; 43 } 44 45 /** 46 * <ol> 47 * <li>Resolve the current expression using the embedded {@link ValueSource}</li> 48 * <li>Retrieve the last expression processed by this value source</li> 49 * <li>Pass the last expression (which should be the function name), along 50 * with the value for the current expression, into the 51 * executeFunction(..) method</li> 52 * <li>Return the result of the executeFunction(..) as the resolved value 53 * for the current expression.</li> 54 * </ol> 55 */ 56 public Object getValue(String expression) { 57 Object value = valueSource.getValue(expression); 58 59 String expr = expression; 60 61 if (valueSource instanceof QueryEnabledValueSource) { 62 expr = ((QueryEnabledValueSource) valueSource).getLastExpression(); 63 } 64 65 return executeFunction(expr, value); 66 } 67 68 /** 69 * Retrieve the embedded value source. 70 * @return {@link ValueSource} 71 */ 72 protected ValueSource getValueSource() { 73 return valueSource; 74 } 75 76 /** 77 * Execute the function referenced in the last-processed expression using the 78 * value resolved from the current expression (using the embedded {@link ValueSource}). 79 * 80 * @param expression The last expression to be processed by this value source. 81 * @param value The value for the current expression, resolved by the embedded {@link ValueSource} 82 * @return The result of modifying the current expression's value using the function named by the last expression. 83 */ 84 protected abstract Object executeFunction(String expression, Object value); 85 }