Adding null handling for missing file read (and test case)

Author: PicoCreator

src/main/java/picoded/dstack/mongodb/MongoDB_FileWorkspaceMap.java

@@ -637,7 +637,15 @@ public void backend_fileWriteInputStream(final String oid, final String filepath
 	 **/
 	@Override
 	public byte[] backend_fileRead(String oid, String filepath) {
+		// Get the buffer
 		InputStream buffer = backend_fileReadInputStream(oid, filepath);
+		
+		// Null handling
+		if( buffer == null ) {
+			return null;
+		}
+		
+		// Cast the inputstream to byte[]
 		byte[] ret = null;
 		try {
 			ret = IOUtils.toByteArray(buffer);
@@ -667,7 +675,17 @@ public byte[] backend_fileRead(String oid, String filepath) {
 	 * @return  the stored byte array of the file
 	 **/
 	public InputStream backend_fileReadInputStream(String oid, String filepath) {
-		return gridFSBucket.openDownloadStream(oid + "/" + filepath);
+		try {
+			return gridFSBucket.openDownloadStream(oid + "/" + filepath);
+		} catch(Exception e) {
+			if( e.getMessage().toLowerCase().indexOf("no file found") >= 0 ) {
+				// Does nothing if no file is found
+				return null;
+			} 
+
+			// rethrow the error
+			throw e;
+		}
 	}
 
 	@Override

src/test/java/picoded/dstack/struct/simple/StructSimple_FileWorkspaceMap_test.java

@@ -144,6 +144,24 @@ public void folderSetupAndRemove_pathVarients() {
 
 	}
 
+	@Test
+	public void noFileRead_returnsNull() {
+		// Get the file workspace to use
+		FileWorkspace fileWorkspace = testObj.newEntry();
+		assertNotNull(fileWorkspace);
+		
+		// Check for null (no file) for non existant file
+		assertNull(fileWorkspace.readString("test/folder/file.txt"));
+
+		// Write file
+		fileWorkspace.writeString("test/folder/file.txt", "anything");
+		assertTrue(fileWorkspace.fileExist("test/folder/file.txt"));
+		assertEquals(fileWorkspace.readString("test/folder/file.txt"), "anything");
+		
+		// Check for null (no file) for non existant file
+		assertNull(fileWorkspace.readString("test/folder/file-somethingElse.txt"));
+	}
+
 	@Test
 	public void fileWrite_andProperlySetupFolder() {
 		// Get the file workspace to use
@@ -153,6 +171,9 @@ public void fileWrite_andProperlySetupFolder() {
 		// Folder does not exist first
 		assertFalse(fileWorkspace.folderPathExist("test/folder"));
 
+		// Check for null (no file) for non existant file
+		assertNull(fileWorkspace.readString("test/folder/file.txt"));
+
 		// Write file
 		fileWorkspace.writeString("test/folder/file.txt", "anything");
 		assertTrue(fileWorkspace.folderPathExist("test/folder"));