Throw IOException if classifier file is invalid

Author: SamCarlberg

core/src/main/java/edu/wpi/grip/core/sources/ClassifierSource.java

@@ -13,9 +13,14 @@
 
 import org.bytedeco.javacpp.opencv_objdetect.CascadeClassifier;
 
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Paths;
 import java.util.List;
 import java.util.Properties;
 
+import static com.google.common.base.Preconditions.checkArgument;
+
 /**
  * A source for the path to a XML classifier file (e.g. haarcascade_face_default.xml).
  */
@@ -75,8 +80,16 @@ public Properties getProperties() {
   }
 
   @Override
-  public void initialize() {
-    classifierSocket.setValue(new CascadeClassifier(filePath));
+  public void initialize() throws IOException {
+    if (!Files.exists(Paths.get(filePath))) {
+      throw new IOException("File does not exist: " + filePath);
+    }
+    try {
+      classifierSocket.setValue(new CascadeClassifier(filePath));
+    } catch (Exception e) {
+      // OpenCV will throw an exception if given malformed XML
+      throw new IOException("Could not load cascade classifier XML", e);
+    }
   }
 
   public interface Factory {

ui/src/main/java/edu/wpi/grip/ui/pipeline/AddSourceButton.java

@@ -272,7 +272,7 @@ public class AddSourceButton extends MenuButton {
           File file = fc.showOpenDialog(getScene().getWindow());
           if (file != null) {
             ClassifierSource source = classifierSourceFactory.create(file.getAbsolutePath());
-            source.initialize();
+            source.initializeSafely();
             eventBus.post(new SourceAddedEvent(source));
           }
         });