Fix resource leaks in core file processing classes

- Add try-with-resources for FileInputStream in ZUGFeRDVisualizer
- Fix unclosed InputStream in ZUGFeRDInvoiceImporter with try-with-resources
- Add explicit close() call for XMLWriter in ZUGFeRDValidator
- Properly close DataInputStream in ZUGFeRDExporterFromPDFA
- Fix resource management in Main.convertInputStreamToString

Mustang-CLI/src/main/java/org/mustangproject/commandline/Main.java

@@ -307,12 +307,13 @@ public class Main {
 	// Plain Java
 	// based on https://mkyong.com/java/how-to-convert-inputstream-to-string-in-java/
 	private static String convertInputStreamToString(InputStream is) {
+		try (InputStream inputStream = is) {
 			int DEFAULT_BUFFER_SIZE = 8192;
 			ByteArrayOutputStream result = new ByteArrayOutputStream();
 			byte[] buffer = new byte[DEFAULT_BUFFER_SIZE];
 			int length;
-		try {
+
-			while ((length = is.read(buffer)) != -1) {
+			while ((length = inputStream.read(buffer)) != -1) {
 				result.write(buffer, 0, length);
 			}
 
@@ -320,11 +321,10 @@ public class Main {
 			return result.toString(StandardCharsets.UTF_8.name());
 		} catch (IOException e) {
 			e.printStackTrace();
-		}
 			return null;
 			// Java 10
 			// return result.toString(StandardCharsets.UTF_8);
-
+		}
 	}
 
 	/***

library/src/main/java/org/mustangproject/XMLTools.java

@@ -220,6 +220,7 @@ public class XMLTools extends XMLWriter {
 	}
 
 	public static byte[] getBytesFromStream(InputStream fileinput) throws IOException {
+		// Stream closing responsibility is with the caller
 		return IOUtils.toByteArray(fileinput);
 	}
 

library/src/main/java/org/mustangproject/ZUGFeRD/ZUGFeRDExporterFromPDFA.java

@@ -90,10 +90,11 @@ public class ZUGFeRDExporterFromPDFA implements IZUGFeRDExporter {
 
 	protected byte[] inputstreamToByteArray(InputStream fileInputStream) throws IOException  {
 		byte[] bytes = new byte[fileInputStream.available()];
-		DataInputStream dataInputStream = new DataInputStream(fileInputStream);
+		try (DataInputStream dataInputStream = new DataInputStream(fileInputStream)) {
 			dataInputStream.readFully(bytes);
 			return bytes;
 		}
+	}
 
 	/***
 	 *

library/src/main/java/org/mustangproject/ZUGFeRD/ZUGFeRDInvoiceImporter.java

@@ -138,9 +138,9 @@ public class ZUGFeRDInvoiceImporter {
 					return;
 				}
 
-				final InputStream XMP = doc.getDocumentCatalog().getMetadata().exportXMPMetadata();
+				try (final InputStream XMP = doc.getDocumentCatalog().getMetadata().exportXMPMetadata()) {
-
 					xmpString = new String(XMLTools.getBytesFromStream(XMP), StandardCharsets.UTF_8);
+				}
 
 				final PDEmbeddedFilesNameTreeNode etn = names.getEmbeddedFiles();
 				if (etn == null) {

library/src/main/java/org/mustangproject/ZUGFeRD/ZUGFeRDVisualizer.java

@@ -131,9 +131,10 @@ public class ZUGFeRDVisualizer {
 
 	public String visualize(String xmlFilename, Language lang)
 		throws IOException, TransformerException, ParserConfigurationException {
-		FileInputStream fis = new FileInputStream(xmlFilename);
+		try (FileInputStream fis = new FileInputStream(xmlFilename)) {
 			return visualize(fis, lang);
 		}
+	}
 
 	public String visualize(InputStream inputXml, Language lang)
 		throws IOException, TransformerException, ParserConfigurationException {
@@ -222,13 +223,15 @@ public class ZUGFeRDVisualizer {
 
 	protected String toFOP(String xmlFilename)
 		throws IOException, TransformerException, ParserConfigurationException {
+		EStandard theStandard;
+		try (FileInputStream fis = new FileInputStream(xmlFilename)) {
+			theStandard = findOutStandardFromRootNode(fis);
+		}
 		
-		FileInputStream fis = new FileInputStream(xmlFilename);
+		try (FileInputStream fis = new FileInputStream(xmlFilename)) {
-		EStandard theStandard = findOutStandardFromRootNode(fis);
-		fis = new FileInputStream(xmlFilename);//rewind :-(
-
 			return toFOP(fis, theStandard);
 		}
+	}
 
 	protected String toFOP(InputStream is, EStandard theStandard)
 		throws TransformerException, IOException {

validator/src/main/java/org/mustangproject/validator/ZUGFeRDValidator.java

@@ -301,6 +301,7 @@ public class ZUGFeRDValidator {
 		XMLWriter writer = new XMLWriter(sw, format);
 		try {
 			writer.write(document);
+			writer.close();
 		} catch (Exception e) {
 			LOGGER.error(e.getMessage());
 		}