Change translateToDataflow to return Operator

Before, translateToDataflow of SingleInputOperator could only return
a single input operator of the lower layer, same for TwoInputOperator.

This change allows translateToDataflow to return more kinds of
operators.

flink-java/src/main/java/org/apache/flink/api/java/operators/OperatorTranslation.java

@@ -111,7 +111,7 @@ public class OperatorTranslation {
 	}
 	
 	
-	private <I, O> org.apache.flink.api.common.operators.SingleInputOperator<?, O, ?> translateSingleInputOperator(SingleInputOperator<?, ?, ?> op) {
+	private <I, O> org.apache.flink.api.common.operators.Operator<O> translateSingleInputOperator(SingleInputOperator<?, ?, ?> op) {
 		
 		@SuppressWarnings("unchecked")
 		SingleInputOperator<I, O, ?> typedOp = (SingleInputOperator<I, O, ?>) op;
@@ -121,26 +121,30 @@ public class OperatorTranslation {
 		
 		Operator<I> input = translate(typedInput);
 		
-		org.apache.flink.api.common.operators.SingleInputOperator<?, O, ?> dataFlowOp = typedOp.translateToDataFlow(input);
+		org.apache.flink.api.common.operators.Operator<O> dataFlowOp = typedOp.translateToDataFlow(input);
 		
-		if (op instanceof UdfOperator<?> ) {
+		if (op instanceof UdfOperator<?>) {
 			@SuppressWarnings("unchecked")
 			SingleInputUdfOperator<I, O, ?> udfOp = (SingleInputUdfOperator<I, O, ?>) op;
-			
+
 			// set configuration parameters
 			Configuration opParams = udfOp.getParameters();
 			if (opParams != null) {
 				dataFlowOp.getParameters().addAll(opParams);
 			}
-			
-			// set the semantic properties
-			dataFlowOp.setSemanticProperties(udfOp.getSemanticProperties());
+
+			if (dataFlowOp instanceof org.apache.flink.api.common.operators.SingleInputOperator) {
+				org.apache.flink.api.common.operators.SingleInputOperator<?, O, ?> unaryOp =
+						(org.apache.flink.api.common.operators.SingleInputOperator<?, O, ?>) dataFlowOp;
+				// set the semantic properties
+				unaryOp.setSemanticProperties(udfOp.getSemanticProperties());
+			}
 		}
 		
 		return dataFlowOp;
 	}
 	
-	private <I1, I2, O> org.apache.flink.api.common.operators.DualInputOperator<?, ?, O, ?> translateTwoInputOperator(TwoInputOperator<?, ?, ?, ?> op) {
+	private <I1, I2, O> org.apache.flink.api.common.operators.Operator<O> translateTwoInputOperator(TwoInputOperator<?, ?, ?, ?> op) {
 		
 		@SuppressWarnings("unchecked")
 		TwoInputOperator<I1, I2, O, ?> typedOp = (TwoInputOperator<I1, I2, O, ?>) op;
@@ -153,7 +157,7 @@ public class OperatorTranslation {
 		Operator<I1> input1 = translate(typedInput1);
 		Operator<I2> input2 = translate(typedInput2);
 		
-		org.apache.flink.api.common.operators.DualInputOperator<?, ?, O, ?> dataFlowOp = typedOp.translateToDataFlow(input1, input2);
+		org.apache.flink.api.common.operators.Operator<O> dataFlowOp = typedOp.translateToDataFlow(input1, input2);
 		
 		if (op instanceof UdfOperator<?> ) {
 			@SuppressWarnings("unchecked")
@@ -164,9 +168,13 @@ public class OperatorTranslation {
 			if (opParams != null) {
 				dataFlowOp.getParameters().addAll(opParams);
 			}
-			
-			// set the semantic properties
-			dataFlowOp.setSemanticProperties(udfOp.getSemanticProperties());
+
+			if (dataFlowOp instanceof org.apache.flink.api.common.operators.DualInputOperator) {
+				org.apache.flink.api.common.operators.DualInputOperator<?, ?,  O, ?> binaryOp =
+						(org.apache.flink.api.common.operators.DualInputOperator<?, ?, O, ?>) dataFlowOp;
+				// set the semantic properties
+				binaryOp.setSemanticProperties(udfOp.getSemanticProperties());
+			}
 		}
 		
 		return dataFlowOp;

flink-java/src/main/java/org/apache/flink/api/java/operators/SingleInputOperator.java

@@ -62,7 +62,7 @@ public abstract class SingleInputOperator<IN, OUT, O extends SingleInputOperator
 	 * @param input The data flow operator that produces this operation's input data.
 	 * @return The translated data flow operator.
 	 */
-	protected abstract org.apache.flink.api.common.operators.SingleInputOperator<?, OUT, ?> translateToDataFlow(
+	protected abstract org.apache.flink.api.common.operators.Operator<OUT> translateToDataFlow(
 			org.apache.flink.api.common.operators.Operator<IN> input);
 	
 }

flink-java/src/main/java/org/apache/flink/api/java/operators/TwoInputOperator.java

@@ -87,6 +87,6 @@ public abstract class TwoInputOperator<IN1, IN2, OUT, O extends TwoInputOperator
 	 * @param input2 The second input of the operation, as a common API operator.
 	 * @return The created common API operator.
 	 */
-	protected abstract org.apache.flink.api.common.operators.DualInputOperator<?, ?, OUT, ?> translateToDataFlow(
+	protected abstract org.apache.flink.api.common.operators.Operator<OUT> translateToDataFlow(
 			org.apache.flink.api.common.operators.Operator<IN1> input1, org.apache.flink.api.common.operators.Operator<IN2> input2);
 }