[github-254] Implement XSSFWorkbook linkExternalWorkbook. Thanks to @aspojo. This closes #254

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1893728 13f79535-47bb-0310-9956-ffa450edef68

poi-integration/build.gradle

     testImplementation 'org.apache.ant:ant:1.10.11'
     testImplementation 'org.apache.commons:commons-collections4:4.4'
     testImplementation 'com.google.guava:guava:31.0.1-jre'
-    testRuntimeOnly 'org.slf4j:slf4j-api:1.7.32'
+    testRuntimeOnly "org.apache.logging.log4j:log4j-core:${log4jVersion}"
+    testRuntimeOnly "org.apache.logging.log4j:log4j-slf4j-impl:${log4jVersion}"
 
     misc(project(':poi-ooxml')) {
         capabilities {

poi-ooxml/src/main/java/org/apache/poi/xssf/usermodel/XSSFCreationHelper.java

 
 import org.apache.poi.common.usermodel.HyperlinkType;
 import org.apache.poi.ss.usermodel.CreationHelper;
+import org.apache.poi.ss.usermodel.FormulaEvaluator;
 import org.apache.poi.ss.usermodel.Hyperlink;
+import org.apache.poi.ss.usermodel.Workbook;
 import org.apache.poi.ss.util.AreaReference;
 import org.apache.poi.ss.util.CellReference;
 import org.apache.poi.util.Internal;
 import org.openxmlformats.schemas.spreadsheetml.x2006.main.CTColor;
 
+import java.util.HashMap;
+import java.util.Map;
+
 public class XSSFCreationHelper implements CreationHelper {
     private final XSSFWorkbook workbook;
+    private final Map<String, Workbook> referencedWorkbooks;
 
     /**
      * Should only be called by {@link XSSFWorkbook#getCreationHelper()}
     @Internal
     public XSSFCreationHelper(XSSFWorkbook wb) {
         workbook = wb;
+        referencedWorkbooks = new HashMap<>();
     }
 
     /**
      */
     @Override
     public XSSFFormulaEvaluator createFormulaEvaluator() {
-        return new XSSFFormulaEvaluator(workbook);
+        XSSFFormulaEvaluator evaluator = new XSSFFormulaEvaluator(workbook);
+        Map<String, FormulaEvaluator> evaluatorMap = new HashMap<>();
+        evaluatorMap.put("", evaluator);
+        this.referencedWorkbooks.forEach((name,otherWorkbook)->evaluatorMap.put(name,otherWorkbook.getCreationHelper().createFormulaEvaluator()));
+        evaluator.setupReferencedWorkbooks(evaluatorMap);
+        return evaluator;
     }
 
     /**
     public AreaReference createAreaReference(CellReference topLeft, CellReference bottomRight) {
         return new AreaReference(topLeft, bottomRight, workbook.getSpreadsheetVersion());
     }
+
+    protected Map<String, Workbook> getReferencedWorkbooks() {
+        return referencedWorkbooks;
+    }
+
+    protected void addExternalWorkbook(String name, Workbook workbook) {
+        this.referencedWorkbooks.put(name,workbook);
+    }
 }

poi-ooxml/src/main/java/org/apache/poi/xssf/usermodel/XSSFWorkbook.java

         namedRangesByName = new ArrayListValuedHashMap<>();
         sheets = new ArrayList<>();
         pivotTables = new ArrayList<>();
+
+        externalLinks = new ArrayList<>();
     }
 
     private void setBookViewsIfMissing() {
      *  referencing the specified external workbook to be added to this one. Allows
      *  formulas such as "[MyOtherWorkbook.xlsx]Sheet3!$A$5" to be added to the
      *  file, for workbooks not already linked / referenced.
-     *
-     *  Note: this is not implemented and thus currently throws an Exception stating this.
+     * <p>
+     * This support is still regarded as in beta and may change
+     * <p>
+     * see https://bz.apache.org/bugzilla/show_bug.cgi?id=57184
      *
      * @param name The name the workbook will be referenced as in formulas
      * @param workbook The open workbook to fetch the link required information from
-     *
-     * @throws RuntimeException stating that this method is not implemented yet.
+     * @return index position for external workbook
+     * @since POI 5.1.0
      */
+    @Beta
     @Override
-    @NotImplemented
     public int linkExternalWorkbook(String name, Workbook workbook) {
-        throw new RuntimeException("Not Implemented - see bug #57184");
+        int externalLinkIdx=-1;
+        if (!getCreationHelper().getReferencedWorkbooks().containsKey(name)){
+             externalLinkIdx = this.getNextPartNumber(XSSFRelation.EXTERNAL_LINKS,
+                    this.getPackagePart().getPackage().getPartsByContentType(XSSFRelation.EXTERNAL_LINKS.getContentType()).size());
+            POIXMLDocumentPart.RelationPart rp = this.createRelationship(XSSFRelation.EXTERNAL_LINKS, XSSFFactory.getInstance(), externalLinkIdx, false);
+            ExternalLinksTable linksTable = rp.getDocumentPart();
+            linksTable.setLinkedFileName(name);
+            this.getExternalLinksTable().add(linksTable);
+
+            CTExternalReference ctExternalReference = this.getCTWorkbook().addNewExternalReferences().addNewExternalReference();
+            ctExternalReference.setId(rp.getRelationship().getId());
+
+        } else {
+            List<RelationPart> relationParts = getRelationParts();
+            for (RelationPart relationPart : relationParts) {
+                if (relationPart.getDocumentPart() instanceof ExternalLinksTable) {
+                    ExternalLinksTable linksTable = relationPart.getDocumentPart();
+                    String linkedFileName = linksTable.getLinkedFileName();
+                    if(linkedFileName.equals(name)){
+                        String s = relationPart.getRelationship().getTargetURI().toString();
+                        String s2 = XSSFRelation.EXTERNAL_LINKS.getDefaultFileName();
+                        String numStr = s.substring(s2.indexOf('#'), s2.indexOf('.'));
+                        externalLinkIdx = Integer.parseInt(numStr);
+                        break;
+                    }
+                }
+            }
+        }
+
+        XSSFCreationHelper creationHelper = getCreationHelper();
+        creationHelper.addExternalWorkbook(name,workbook);
+
+        return externalLinkIdx;
+
     }
 
     /**

poi-ooxml/src/test/java/org/apache/poi/xssf/usermodel/TestXSSFWorkbook.java

 
 import static org.apache.commons.io.output.NullOutputStream.NULL_OUTPUT_STREAM;
 import static org.apache.poi.hssf.HSSFTestDataSamples.openSampleFileStream;
-import static org.apache.poi.xssf.XSSFTestDataSamples.openSampleWorkbook;
-import static org.apache.poi.xssf.XSSFTestDataSamples.writeOut;
-import static org.apache.poi.xssf.XSSFTestDataSamples.writeOutAndReadBack;
+import static org.apache.poi.xssf.XSSFTestDataSamples.*;
 import static org.junit.jupiter.api.Assertions.assertArrayEquals;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import java.util.Date;
 import java.util.Iterator;
 import java.util.List;
+import java.util.function.Consumer;
 import java.util.zip.CRC32;
 
 import org.apache.poi.POIDataSamples;
 import org.apache.poi.xddf.usermodel.chart.XDDFBarChartData;
 import org.apache.poi.xddf.usermodel.chart.XDDFChartData;
 import org.apache.poi.xssf.XSSFITestDataProvider;
+import org.apache.poi.xssf.XSSFTestDataSamples;
 import org.apache.poi.xssf.model.StylesTable;
 import org.junit.jupiter.api.Test;
 import org.openxmlformats.schemas.spreadsheetml.x2006.main.CTCalcPr;
     private static String ref(Cell cell) {
         return new CellReference(cell).formatAsString();
     }
+
+    @Test
+    void testLinkExternalWorkbook() throws Exception {
+        String nameA = "link-external-workbook-a.xlsx";
+
+        try (
+                XSSFWorkbook a = new XSSFWorkbook();
+                XSSFWorkbook b = new XSSFWorkbook()
+        ) {
+            XSSFRow row1 = a.createSheet().createRow(0);
+            row1.createCell(0).setCellValue(10);
+            row1.createCell(1).setCellValue(20);
+
+            XSSFRow row2 = b.createSheet().createRow(0);
+            XSSFCell cell = row2.createCell(0);
+
+            b.linkExternalWorkbook(nameA, a);
+            String formula = String.format("SUM('[%s]Sheet0'!A1:B1)", nameA);
+            cell.setCellFormula(formula);
+            XSSFFormulaEvaluator evaluator = b.getCreationHelper().createFormulaEvaluator();
+            evaluator.evaluateFormulaCell(cell);
+            double cellValue = cell.getNumericCellValue();
+            assertEquals(cellValue,30.0);
+            /*
+            try (FileOutputStream out = new FileOutputStream(getSampleFile(nameA))) {
+                a.write(out);
+            }
+            String nameB = "link-external-workbook-b.xlsx";
+            try (FileOutputStream out = new FileOutputStream(getSampleFile(nameB))) {
+                b.write(out);
+            }
+            */
+        }
+    }
+
 }