samples: Adding samples for updating & querying Proto messages & enums (#2211)

* samples: Adding samples for updating & querying Proto messages & enums

* style: linting

* style: linting

* docs: Adding function and class doc

Author: gauravpurohit06

samples/snippets/src/main/java/com/example/spanner/QueryProtoColumnSample.java

@@ -0,0 +1,78 @@
+/*
+ * Copyright 2022 Google Inc.
+ *
+ * Licensed 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 com.example.spanner;
+
+import com.example.spanner.SingerProto.Genre;
+import com.example.spanner.SingerProto.SingerInfo;
+import com.google.cloud.spanner.DatabaseClient;
+import com.google.cloud.spanner.DatabaseId;
+import com.google.cloud.spanner.ResultSet;
+import com.google.cloud.spanner.Spanner;
+import com.google.cloud.spanner.SpannerOptions;
+import com.google.cloud.spanner.Statement;
+
+/**
+ * To query Proto column including messages and enums and array of them.
+ */
+public class QueryProtoColumnSample {
+
+  static void queryProtoColumn() {
+    // TODO(developer): Replace these variables before running the sample.
+    String projectId = "my-project";
+    String instanceId = "my-instance";
+    String databaseId = "my-database";
+
+    try (Spanner spanner =
+        SpannerOptions.newBuilder().setProjectId(projectId).build().getService()) {
+      DatabaseClient client =
+          spanner.getDatabaseClient(DatabaseId.of(projectId, instanceId, databaseId));
+      queryProtoColumn(client);
+    }
+  }
+
+  /**
+   * Method to query Singer Table using DQL.
+   *
+   * Assuming a table Singer with columns with following DDL:
+   * CREATE TABLE Singer (
+   *     singer_id        INT64 NOT NULL,
+   *     singer_info    spanner.examples.music.SingerInfo,
+   *     genre   spanner.examples.music.Genre,
+   *     singer_info_list   ARRAY<spanner.examples.music.SingerInfo>,
+   *     genre_list  ARRAY<spanner.examples.music.Genre>,
+   * ) PRIMARY KEY (singer_id);
+   */
+  static void queryProtoColumn(DatabaseClient client) {
+    Statement statement =
+        Statement.newBuilder(
+                "SELECT singer_id, singer_info, genre, singer_info_list, genre_list\n"
+                    + "FROM Singer")
+            .build();
+
+    try (ResultSet resultSet = client.singleUse().executeQuery(statement)) {
+      while (resultSet.next()) {
+        System.out.printf(
+            "singer_id: %s, singer_info: %s , genre: %s, "
+                + "singer_info_list: %s, genre_list: %s%n ",
+            resultSet.getLong("singer_id"),
+            resultSet.getProtoMessage("singer_info", SingerInfo.getDefaultInstance()),
+            resultSet.getProtoEnum("genre", Genre::forNumber),
+            resultSet.getProtoMessageList("singer_info_list", SingerInfo.getDefaultInstance()),
+            resultSet.getProtoEnumList("genre_list", Genre::forNumber));
+      }
+    }
+  }
+}