/* ==================================================================== Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements. See the NOTICE file distributed with this work for additional information regarding copyright ownership. The ASF licenses this file to You 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.poi.hssf.record.formula.eval; /** * This class is used to simplify error handling logic within operator and function * implementations. Note - OperationEval.evaluate() and Function.evaluate() * method signatures do not throw this exception so it cannot propagate outside.
* * Here is an example coded without EvaluationException, to show how it can help: ** public Eval evaluate(Eval[] args, int srcRow, short srcCol) { * // ... * Eval arg0 = args[0]; * if(arg0 instanceof ErrorEval) { * return arg0; * } * if(!(arg0 instanceof AreaEval)) { * return ErrorEval.VALUE_INVALID; * } * double temp = 0; * AreaEval area = (AreaEval)arg0; * ValueEval[] values = area.getValues(); * for (int i = 0; i < values.length; i++) { * ValueEval ve = values[i]; * if(ve instanceof ErrorEval) { * return ve; * } * if(!(ve instanceof NumericValueEval)) { * return ErrorEval.VALUE_INVALID; * } * temp += ((NumericValueEval)ve).getNumberValue(); * } * // ... * } ** In this example, if any error is encountered while processing the arguments, an error is * returned immediately. This code is difficult to refactor due to all the points where errors * are returned.
* public Eval evaluate(Eval[] args, int srcRow, short srcCol) { * try { * // ... * AreaEval area = getAreaArg(args[0]); * double temp = sumValues(area.getValues()); * // ... * } catch (EvaluationException e) { * return e.getErrorEval(); * } *} * *private static AreaEval getAreaArg(Eval arg0) throws EvaluationException { * if (arg0 instanceof ErrorEval) { * throw new EvaluationException((ErrorEval) arg0); * } * if (arg0 instanceof AreaEval) { * return (AreaEval) arg0; * } * throw EvaluationException.invalidValue(); *} * *private double sumValues(ValueEval[] values) throws EvaluationException { * double temp = 0; * for (int i = 0; i < values.length; i++) { * ValueEval ve = values[i]; * if (ve instanceof ErrorEval) { * throw new EvaluationException((ErrorEval) ve); * } * if (!(ve instanceof NumericValueEval)) { * throw EvaluationException.invalidValue(); * } * temp += ((NumericValueEval) ve).getNumberValue(); * } * return temp; *} ** It is not mandatory to use EvaluationException, doing so might give the following advantages: