enable to import multiple spotbugs.xml results file

build.gradle

@@ -79,7 +79,9 @@ dependencies {
         exclude group: 'org.apache.logging.log4j', module: 'log4j-core'
         exclude group: 'org.slf4j', module: 'slf4j-api'
     }
-    implementation 'net.sf.saxon:Saxon-HE:12.5'
+    implementation ('net.sf.saxon:Saxon-HE:12.5') {
+        exclude group: 'org.slf4j', module: 'slf4j-api'
+    }
     implementation 'org.jsoup:jsoup:1.18.3'
     implementation 'info.clearthought:table-layout:4.3.0'
     testImplementation 'junit:junit:4.13.2'

src/main/java/org/jetbrains/plugins/spotbugs/actions/ImportBugCollection.java

@@ -81,10 +81,12 @@ void actionPerformedImpl(
 		if (dialogBuilder.getDialogWrapper().getExitCode() == DialogWrapper.CANCEL_EXIT_CODE) {
 			return;
 		}
-		final String fileToImport = importFileDialog.getText();
-		if (fileToImport == null || fileToImport.trim().isEmpty()) {
-			return;
-		}
+        String inputFile = importFileDialog.getText();
+        inputFile = MergeMultipleResultsFiles.mergeFiles(inputFile);
+        if (inputFile == null || inputFile.trim().isEmpty()) {
+            return;
+        }
+        final String fileToImport = inputFile;
 
 
 		final FindBugsResult findBugsResult = ToolWindowPanel.getInstance(project).getResult();

src/main/java/org/jetbrains/plugins/spotbugs/actions/MergeMultipleResultsFiles.java

@@ -0,0 +1,138 @@
+/*
+ * Copyright 2020 SpotBugs plugin contributors
+ *
+ * This file is part of IntelliJ SpotBugs plugin.
+ *
+ * IntelliJ SpotBugs plugin is free software: you can redistribute it
+ * and/or modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, either version 3 of
+ * the License, or (at your option) any later version.
+ *
+ * IntelliJ SpotBugs plugin is distributed in the hope that it will
+ * be useful, but WITHOUT ANY WARRANTY; without even the implied
+ * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ * See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with IntelliJ SpotBugs plugin.
+ * If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package org.jetbrains.plugins.spotbugs.actions;
+
+import org.w3c.dom.Document;
+import org.w3c.dom.Element;
+import org.w3c.dom.Node;
+import org.w3c.dom.NodeList;
+import org.xml.sax.SAXException;
+
+import javax.xml.parsers.DocumentBuilder;
+import javax.xml.parsers.DocumentBuilderFactory;
+import javax.xml.parsers.ParserConfigurationException;
+import javax.xml.transform.Transformer;
+import javax.xml.transform.TransformerFactory;
+import javax.xml.transform.dom.DOMSource;
+import javax.xml.transform.stream.StreamResult;
+import java.io.File;
+import java.io.FileWriter;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.ArrayList;
+import java.util.List;
+
+public class MergeMultipleResultsFiles {
+
+    public static String mergeFiles(final String inputFile){
+
+        if (inputFile == null || inputFile.trim().isEmpty()) {
+            return null;
+        }
+
+        if (!Files.isDirectory(Path.of(inputFile))){
+            return inputFile;
+        }
+
+        final String outputFile = Path.of(inputFile, "merged-spotbugs-report.xml").toString();
+        // input file is directory - go over all the directories under this folder,
+        // find spotbugs results file and merge them to one file
+        try {
+            final List<File> xmlFiles = new ArrayList<>();
+            collectXmlFiles(new File(inputFile), xmlFiles);
+
+            if (xmlFiles.isEmpty()) {
+                System.out.println("No SpotBugs XML files found in the directory: " + inputFile);
+                return null;
+            }
+
+            final Document mergedDocument = mergeSpotBugsReports(xmlFiles);
+
+            saveDocumentToFile(mergedDocument, outputFile);
+            System.out.println("Merged SpotBugs report written to: " + outputFile);
+        } catch (Exception e) {
+            System.err.println("Error while merging SpotBugs reports: " + e.getMessage());
+            e.printStackTrace();
+        }
+        return outputFile;
+    }
+
+    /**
+     * Recursively collects XML files from the given directory.
+     */
+    private static void collectXmlFiles(File directory, List<File> xmlFiles) {
+        if (!directory.exists()) {
+            System.err.println("Directory does not exist: " + directory.getAbsolutePath());
+            return;
+        }
+
+        final File[] files = directory.listFiles();
+        if (files != null) {
+            for (File file : files) {
+                if (file.isDirectory()) {
+                    collectXmlFiles(file, xmlFiles);
+                } else if (file.getName().equals("spotbugsXml.xml")) {
+                    System.out.println("adding file "+ file);
+                    xmlFiles.add(file);
+                }
+            }
+        }
+    }
+
+    /**
+     * Merges multiple SpotBugs XML files into a single Document.
+     */
+    private static Document mergeSpotBugsReports(List<File> xmlFiles)
+        throws ParserConfigurationException, SAXException, IOException {
+
+        final DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
+        final DocumentBuilder builder = factory.newDocumentBuilder();
+        final Document mergedDocument = builder.newDocument();
+
+        // Create the root element for the merged document
+        Element rootElement = mergedDocument.createElement("BugCollection");
+        mergedDocument.appendChild(rootElement);
+
+        for (File file : xmlFiles) {
+            final Document document = builder.parse(file);
+            final NodeList bugInstances = document.getElementsByTagName("BugInstance");
+
+            for (int i = 0; i < bugInstances.getLength(); i++) {
+                final Node importedNode = mergedDocument.importNode(bugInstances.item(i), true);
+                rootElement.appendChild(importedNode);
+            }
+        }
+
+        return mergedDocument;
+    }
+
+    /**
+     * Saves the merged Document to an XML file.
+     */
+    private static void saveDocumentToFile(Document document, String outputFile) throws Exception {
+        final TransformerFactory transformerFactory = TransformerFactory.newInstance();
+        final Transformer transformer = transformerFactory.newTransformer();
+        final DOMSource source = new DOMSource(document);
+        final StreamResult result = new StreamResult(new FileWriter(outputFile));
+        transformer.transform(source, result);
+    }
+}