hililiwei commented on a change in pull request #2969:
URL: https://github.com/apache/iceberg/pull/2969#discussion_r699386820



##########
File path: flink/src/main/java/org/apache/iceberg/flink/util/FlinkScalaUtil.java
##########
@@ -0,0 +1,36 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.apache.iceberg.flink.util;
+
+import org.apache.flink.streaming.api.scala.DataStream;
+
+public class FlinkScalaUtil {
+  private FlinkScalaUtil() {
+  }
+
+  /**
+   * Converts an [[org.apache.flink.streaming.api.datastream.DataStream]] to a
+   * [[org.apache.flink.streaming.api.scala.DataStream]].
+   */
+  public static <T> DataStream<T> asScalaStream(
+      org.apache.flink.streaming.api.datastream.DataStream<T> javaDataStream) {
+    return new DataStream<>(javaDataStream);
+  }

Review comment:
       For example, there is a method named env in the FlinkSourcre class. The 
method signature includes a Java StreamExecutionEnvironment parameter. In order 
to prevent developers who use scala from explicitly converting the scala 
StreamExecutionEnvironment class to the java StreamExecutionEnvironment class, 
I use the subclass Builder to provide A method that contains the parameters of 
scala's StreamExecutionEnvironment

##########
File path: flink/src/main/java/org/apache/iceberg/flink/sink/FlinkSink.java
##########
@@ -117,7 +109,7 @@ public static Builder forRowData(DataStream<RowData> input) 
{
     return new Builder().forRowData(input);
   }
 
-  public static class Builder {
+  public static class Builder<T extends Builder<T>> {

Review comment:
       > I'm not quite sure I understand why this templating addition is 
needed. Could you help clarify that for me?
   
   If don't add this templating, when the subclass Builder instance calls the 
parent Builder's method, it will return an instance of the parent Builder,  and 
we won't be able to access the subclass Builer method.

##########
File path: flink/src/main/java/org/apache/iceberg/flink/util/FlinkScalaUtil.java
##########
@@ -0,0 +1,36 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.apache.iceberg.flink.util;
+
+import org.apache.flink.streaming.api.scala.DataStream;
+
+public class FlinkScalaUtil {
+  private FlinkScalaUtil() {
+  }
+
+  /**
+   * Converts an [[org.apache.flink.streaming.api.datastream.DataStream]] to a
+   * [[org.apache.flink.streaming.api.scala.DataStream]].
+   */
+  public static <T> DataStream<T> asScalaStream(
+      org.apache.flink.streaming.api.datastream.DataStream<T> javaDataStream) {
+    return new DataStream<>(javaDataStream);
+  }

Review comment:
       In the code submitted this time, most of the changes are to allow 
developers to directly use variables such as StreamExecutionEnvironment and 
DataStream in scala in FlinkSourceScala or FlinkSinkScala, without the need to 
convert them to Java before using them. Of course, FlinkScalaUtil still 
provides the ability to convert java DataStream to scala.

##########
File path: flink/src/main/java/org/apache/iceberg/flink/util/FlinkScalaUtil.java
##########
@@ -0,0 +1,36 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.apache.iceberg.flink.util;
+
+import org.apache.flink.streaming.api.scala.DataStream;
+
+public class FlinkScalaUtil {
+  private FlinkScalaUtil() {
+  }
+
+  /**
+   * Converts an [[org.apache.flink.streaming.api.datastream.DataStream]] to a
+   * [[org.apache.flink.streaming.api.scala.DataStream]].
+   */
+  public static <T> DataStream<T> asScalaStream(
+      org.apache.flink.streaming.api.datastream.DataStream<T> javaDataStream) {
+    return new DataStream<>(javaDataStream);
+  }

Review comment:
       Because scala was not introduced, I extend  FlinkSource\FlinkSink 
Builder , added several methods to receive scala variables, and changed the 
parent build to use covariance. If you think this is unnecessary, or there are 
other better ways to receive scala variables, please let me know, thank you.




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