closes #39

src/main/java/org/mustangproject/ZUGFeRD/ZUGFeRDExporter.java

@@ -75,6 +75,8 @@ public class ZUGFeRDExporter implements Closeable {
 
 	private boolean disableAutoClose;
 
+	private boolean fileAttached=false;
+
 	public ZUGFeRDExporter() {
 		init();
 	}
@@ -274,7 +276,6 @@ public class ZUGFeRDExporter implements Closeable {
 	 *            <code>setZUGFeRDXMLData(byte[] zugferdData)</code>
 	 */
 	public void PDFattachZugferdFile(IZUGFeRDExportableTransaction trans) throws IOException {
-
 		xmlProvider.generateXML(trans);
 		String filename = getFilenameForVersion(ZFVersion);
 		PDFAttachGenericFile(doc, filename, "Alternative",
@@ -283,6 +284,9 @@ public class ZUGFeRDExporter implements Closeable {
 	}
 
 	public void export(String ZUGFeRDfilename) throws IOException {
+		if (!fileAttached) {
+			throw new IOException("File must be attached (usually with PDFattachZugferdFile) before perfoming this operation");
+		}
 		doc.save(ZUGFeRDfilename);
 		if (!disableAutoClose) {
 			close();
@@ -290,6 +294,9 @@ public class ZUGFeRDExporter implements Closeable {
 	}
 
 	public void export(OutputStream output) throws IOException {
+		if (!fileAttached) {
+			throw new IOException("File must be attached (usually with PDFattachZugferdFile) before perfoming this operation");
+		}
 		doc.save(output);
 		if (!disableAutoClose) {
 			close();
@@ -316,6 +323,8 @@ public class ZUGFeRDExporter implements Closeable {
 	 */
 	public void PDFAttachGenericFile(PDDocument doc, String filename, String relationship, String description,
 			String subType, byte[] data) throws IOException {
+		fileAttached=true;
+
 		PDComplexFileSpecification fs = new PDComplexFileSpecification();
 		fs.setFile(filename);
 

src/test/java/org/mustangproject/ZUGFeRD/MustangReaderWriterCustomXMLTest.java

@@ -183,8 +183,7 @@ public class MustangReaderWriterCustomXMLTest extends TestCase {
 					+ "</ram:SpecifiedTradeProduct>\n" + "</ram:IncludedSupplyChainTradeLineItem>\n"
 					+ "</rsm:SpecifiedSupplyChainTradeTransaction>\n" + "</rsm:CrossIndustryDocument>";
 			zea1.setZUGFeRDXMLData(ownZUGFeRDXML.getBytes("UTF-8"));
-			zea1.PDFattachZugferdFile(null);
-
+			
 			ByteArrayOutputStream baos=new ByteArrayOutputStream();
 			zea1.disableAutoClose(true);
 			zea1.export(TARGET_PDF);

src/test/java/org/mustangproject/ZUGFeRD/MustangReaderWriterEdgeTest.java

@@ -412,7 +412,7 @@ public class MustangReaderWriterEdgeTest extends TestCase implements IZUGFeRDExp
     	  ze.setZUGFeRDVersion(1);
       ze.PDFattachZugferdFile(this);
       String theXML=new String(ze.getProvider().getXML());
-      //assertTrue(theXML.contains("<rsm:CrossIndustryDocument"));
+      assertTrue(theXML.contains("<rsm:CrossIndustryDocument"));
       ze.export(TARGET_PDF);
     }