[GitHub] [beam] robinyqiu commented on a change in pull request #12267: [WIP][BEAM-10408] Schema capable io wrapper pubsub

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robinyqiu commented on a change in pull request #12267:
URL: https://github.com/apache/beam/pull/12267#discussion_r455351279



##########
File path: sdks/java/extensions/sql/src/main/java/org/apache/beam/sdk/extensions/sql/meta/provider/SchemaCapableIOTableProviderWrapper.java
##########
@@ -0,0 +1,136 @@
+/*
+ * 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.beam.sdk.extensions.sql.meta.provider;
+
+import static org.apache.beam.sdk.util.RowJsonUtils.newObjectMapperWith;
+
+import com.alibaba.fastjson.JSONObject;
+import com.fasterxml.jackson.core.JsonProcessingException;
+import java.io.Serializable;
+import org.apache.beam.sdk.annotations.Experimental;
+import org.apache.beam.sdk.annotations.Internal;
+import org.apache.beam.sdk.extensions.sql.impl.BeamTableStatistics;
+import org.apache.beam.sdk.extensions.sql.meta.BaseBeamTable;
+import org.apache.beam.sdk.extensions.sql.meta.BeamSqlTable;
+import org.apache.beam.sdk.extensions.sql.meta.Table;
+import org.apache.beam.sdk.options.PipelineOptions;
+import org.apache.beam.sdk.schemas.Schema;
+import org.apache.beam.sdk.schemas.io.InvalidConfigurationException;
+import org.apache.beam.sdk.schemas.io.InvalidSchemaException;
+import org.apache.beam.sdk.schemas.io.SchemaIO;
+import org.apache.beam.sdk.schemas.io.SchemaIOProvider;
+import org.apache.beam.sdk.transforms.PTransform;
+import org.apache.beam.sdk.util.RowJson;
+import org.apache.beam.sdk.values.PBegin;
+import org.apache.beam.sdk.values.PCollection;
+import org.apache.beam.sdk.values.POutput;
+import org.apache.beam.sdk.values.Row;
+
+/**
+ * A general {@link TableProvider} for IOs for consumption by Beam SQL.
+ *
+ * <p>Can create child classes for IOs to pass {@link #schemaCapableIOProvider} that is specific to
+ * the IO.
+ */
+@Internal
+@Experimental
+public abstract class SchemaCapableIOTableProviderWrapper extends InMemoryMetaTableProvider
+    implements Serializable {
+  private SchemaIOProvider schemaCapableIOProvider;
+
+  public SchemaCapableIOTableProviderWrapper(SchemaIOProvider schemaCapableIOProvider) {
+    this.schemaCapableIOProvider = schemaCapableIOProvider;

Review comment:
       I am guessing it could be this LOC that cause the problem.
   
   I googled about Java service provider and it says a service provider (in this case it is `PubSubJsonTableProvider`) should have a parameterless constructor. But I didn't find if the superclass of a service provider (this file) is also required to have a parameterless constructor.
   
   Could we set 
   
   ```
   private SchemaIOProvider schemaCapableIOProvider = new PubsubSchemaCapableIOProvider();
   ```
   
   here and see if this could fix the problem? I know it is wrong for the general case, but just curious if that could be the fix.




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