log4j/src/testcases/org/apache/poi/ss/formula/eval/forked/BaseTestForkedEvaluator.java

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   this work for additional information regarding copyright ownership.
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package org.apache.poi.ss.formula.eval.forked;

import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertNotNull;
import static org.junit.jupiter.api.Assertions.assertThrows;

import java.io.IOException;

import org.apache.poi.hssf.usermodel.HSSFWorkbook;
import org.apache.poi.ss.formula.IStabilityClassifier;
import org.apache.poi.ss.formula.eval.NumberEval;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.ss.usermodel.Sheet;
import org.apache.poi.ss.usermodel.Workbook;
import org.junit.jupiter.api.Test;

public class BaseTestForkedEvaluator {

    protected Workbook newWorkbook() {
        return new HSSFWorkbook();
    }

	/**
	 * set up a calculation workbook with input cells nicely segregated on a
	 * sheet called "Inputs"
	 */
	protected Workbook createWorkbook() {
		Workbook wb = newWorkbook();
		Sheet sheet1 = wb.createSheet("Inputs");
		Sheet sheet2 = wb.createSheet("Calculations");
		Row row;
		row = sheet2.createRow(0);
		row.createCell(0).setCellFormula("B1*Inputs!A1-Inputs!B1");
		row.createCell(1).setCellValue(5.0); // Calculations!B1

		// some default input values
		row = sheet1.createRow(0);
		row.createCell(0).setCellValue(2.0); // Inputs!A1
		row.createCell(1).setCellValue(3.0); // Inputs!B1
		return wb;
	}

	/**
	 * Shows a basic use-case for {@link ForkedEvaluator}
	 */
	@Test
	void testBasic() throws IOException {
		try (Workbook wb = createWorkbook()) {

			// The stability classifier is useful to reduce memory consumption of caching logic
			IStabilityClassifier stabilityClassifier = (sheetIndex, rowIndex, columnIndex) -> sheetIndex == 1;

			ForkedEvaluator fe1 = ForkedEvaluator.create(wb, stabilityClassifier, null);
			ForkedEvaluator fe2 = ForkedEvaluator.create(wb, stabilityClassifier, null);

			// fe1 and fe2 can be used concurrently on separate threads

			fe1.updateCell("Inputs", 0, 0, new NumberEval(4.0));
			fe1.updateCell("Inputs", 0, 1, new NumberEval(1.1));

			fe2.updateCell("Inputs", 0, 0, new NumberEval(1.2));
			fe2.updateCell("Inputs", 0, 1, new NumberEval(2.0));

			NumberEval eval1 = (NumberEval) fe1.evaluate("Calculations", 0, 0);
			assertNotNull(eval1);
			assertEquals(18.9, eval1.getNumberValue(), 0.0);
			NumberEval eval2 = (NumberEval) fe2.evaluate("Calculations", 0, 0);
			assertNotNull(eval2);
			assertEquals(4.0, eval2.getNumberValue(), 0.0);
			fe1.updateCell("Inputs", 0, 0, new NumberEval(3.0));
			eval1 = (NumberEval) fe1.evaluate("Calculations", 0, 0);
			assertNotNull(eval1);
			assertEquals(13.9, eval1.getNumberValue(), 0.0);
		}
	}

	/**
	 * As of Sep 2009, the Forked evaluator can update values from existing cells (this is because
	 * the underlying 'master' cell is used as a key into the calculation cache.  Prior to the fix
	 * for this bug, an attempt to update a missing cell would result in NPE.  This junit tests for
	 * a more meaningful error message.<br>
	 *
	 * An alternate solution might involve allowing empty cells to be created as necessary.  That
	 * was considered less desirable because so far, the underlying 'master' workbook is strictly
	 * <i>read-only</i> with respect to the ForkedEvaluator.
	 */
	@Test
	void testMissingInputCellH() throws IOException {

		try (Workbook wb = createWorkbook()) {
			ForkedEvaluator fe = ForkedEvaluator.create(wb, null, null);
			// attempt update input at cell A2 (which is missing)
			UnsupportedOperationException ex = assertThrows(
				UnsupportedOperationException.class,
				 () -> fe.updateCell("Inputs", 1, 0, new NumberEval(4.0))
			);
			assertEquals("Underlying cell 'A2' is missing in master sheet.", ex.getMessage());
		}
	}
}