Correctly handle transient variables during serializability check

stratosphere-core/src/main/java/eu/stratosphere/api/common/operators/util/UserCodeObjectWrapper.java

@@ -24,21 +24,24 @@
 
 /**
  * This holds an actual object containing user defined code.
- *
  */
 public class UserCodeObjectWrapper<T> implements UserCodeWrapper<T> {
  private static final long serialVersionUID = 1L;
 
- private T userCodeObject;
+ private final T userCodeObject;
 
  public UserCodeObjectWrapper(T userCodeObject) {
- Preconditions.checkArgument(userCodeObject instanceof Serializable, "User code object is not serializable: " + userCodeObject.getClass());
+ Preconditions.checkNotNull(userCodeObject, "The user code object may not be null.");
+ Preconditions.checkArgument(userCodeObject instanceof Serializable, "User code object is not serializable: " + userCodeObject.getClass().getName());
+
  this.userCodeObject = userCodeObject;
- // Remove unserializable objects from the user code object as well as from outer objects
+
+ // Remove non serializable objects from the user code object as well as from outer objects
  Object current = userCodeObject;
  try {
  while (null != current) {
  Object newCurrent = null;
+
  /**
  * Check if the usercode class has custom serialization methods.
  * (See http:https://docs.oracle.com/javase/7/docs/api/java/io/Serializable.html for details).
@@ -53,7 +56,8 @@ public UserCodeObjectWrapper(T userCodeObject) {
  } catch (Exception e) {
  // we can ignore exceptions here.
  }
- if(customSerializer != null && customDeserializer != null) {
+
+ if (customSerializer != null && customDeserializer != null) {
  hasCustomSerialization = true;
  }
 
@@ -64,18 +68,26 @@ public UserCodeObjectWrapper(T userCodeObject) {
  newCurrent = f.get(current);
  }
 
- if (!hasCustomSerialization && !Modifier.isStatic(f.getModifiers()) && f.get(current) != null && !(f.get(current) instanceof Serializable)) {
- throw new RuntimeException("User code object " +
- userCodeObject + " contains non-serializable field " + f.getName() + " = " + f.get(current));
+ if (hasCustomSerialization || Modifier.isTransient(f.getModifiers()) || Modifier.isStatic(f.getModifiers())) {
+ // field not relevant for serialization
+ continue;
+ }
+
+ Object fieldContents = f.get(current);
+ if (fieldContents != null && !(fieldContents instanceof Serializable)) {
+ throw new RuntimeException("User-defined object " + userCodeObject + " (" + 
+ userCodeObject.getClass().getName() + ") contains non-serializable field " +
+ f.getName() + " = " + f.get(current));
  }
  }
  current = newCurrent;
  }
- } catch (IllegalAccessException e) {
- // this cannot occur since we call setAccessible(true)
- e.printStackTrace();
  }
-
+ catch (Exception e) {
+ // should never happen, since we make the fields accessible.
+ // anyways, do not swallow the exception, but report it
+ throw new RuntimeException("Could not access the fields of the user defined class while checking for serializability.", e);
+ }
  }
 
  @Override
@@ -91,7 +103,6 @@ public T getUserCodeObject() {
  Serializable ser = (Serializable) userCodeObject;
  T cloned = (T) SerializationUtils.clone(ser);
  return cloned;
-
  }
 
  @Override