Use try-with-resources to prevent potential resource leaks

* Detected by enabling all resource-related Java compiler warnings
 * Java -> Compiler -> Errors/Warnings
 * Filtering for "resource" should show 3 warnings
 * Set to "Warning"

Issue-Ref: 3539
Issue-Url: https://af3-developer.fortiss.org/issues/3539



Signed-off-by: Simon Barner <barner@fortiss.org>

org.fortiss.tooling.kernel/src/org/fortiss/tooling/kernel/internal/.ratings

 CommandStackService.java 957bda69b5feb91f002aed4d25ed334e92801e7e GREEN
 ConnectionCompositorService.java d69a60cd7a3d06e91d24fd32b9c00125ea71e0dd GREEN
 ConstraintCheckerService.java 459b5eb717598e7e8bb71a0c87e57ea85cb00e4b GREEN
-ConstraintService.java d869107b1cef404bc5e27edd7d30fc2ea86a0427 GREEN
+ConstraintService.java 139187909523300c80a22be920329f1c9d0fb654 YELLOW
 DummyTopLevelElement.java 42ae59a6a89a57035644d04f9f0f2d674797642a GREEN
 ElementCompositorService.java 98c5d27e09881e60aa4f87c1ac0c7787cdec9f7c GREEN
 LibraryPrototypeProvider.java b77eddbdca78f561ffb1233e98817be361c690ae GREEN

org.fortiss.tooling.kernel/src/org/fortiss/tooling/kernel/internal/ConstraintService.java

@@ -202,11 +202,10 @@ public final class ConstraintService implements IIntrospectiveKernelService, ICo
 			return null;
 		}
 		ByteArrayOutputStream baos = new ByteArrayOutputStream();
-		final ObjectOutputStream oos;
 		final EObject hashRelevant = getChecksumRelevantEObject(constrained, ci);
-		try {
+		try(ObjectOutputStream oos = new ObjectOutputStream(baos)) {
 			final ResourceSet rset = new ResourceSetImpl();
-			oos = new ObjectOutputStream(baos);
+
 			Resource resource = rset.createResource(URI.createURI("temp"));
 			resource.getContents().add(hashRelevant);
 			Map<String, String> options = new HashMap<>();
@@ -217,7 +216,6 @@ public final class ConstraintService implements IIntrospectiveKernelService, ICo
 			options.put(OPTION_PROCESS_DANGLING_HREF, OPTION_PROCESS_DANGLING_HREF_DISCARD);
 
 			resource.save(oos, options);
-			oos.close();
 			MessageDigest m = MessageDigest.getInstance("SHA1");
 			m.update(baos.toByteArray());
 			BigInteger res = new BigInteger(1, m.digest());
@@ -227,11 +225,11 @@ public final class ConstraintService implements IIntrospectiveKernelService, ICo
 				String nameCstrd = constrained instanceof INamedElement
 						? ((INamedElement)constrained).getName() : constrained.toString();
 				String fileName = filePrefix + "_" + nameCstr + "_" + nameCstrd + ".xml";
-				FileOutputStream file = new FileOutputStream(fileName);
-				ObjectOutputStream oos2 = new ObjectOutputStream(file);
-				resource.save(oos2, options);
-				oos2.writeUTF("\nCHECKSUM: " + res.toString());
-				oos2.close();
+				try(FileOutputStream file = new FileOutputStream(fileName);
+						ObjectOutputStream oos2 = new ObjectOutputStream(file)) {
+					resource.save(oos2, options);
+					oos2.writeUTF("\nCHECKSUM: " + res.toString());
+				}
 			}
 			resource.getContents().remove(hashRelevant);
 			resource.delete(options);