docs(samples): added extract to json and accompanying test (#416)

samples/snippets/src/main/java/com/example/bigquery/ExtractTableToJson.java

@@ -0,0 +1,85 @@
+/*
+ * Copyright 2020 Google LLC
+ *
+ * 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.bigquery;
+
+// [START bigquery_extract_table_json]
+import com.google.cloud.RetryOption;
+import com.google.cloud.bigquery.BigQuery;
+import com.google.cloud.bigquery.BigQueryException;
+import com.google.cloud.bigquery.BigQueryOptions;
+import com.google.cloud.bigquery.FormatOptions;
+import com.google.cloud.bigquery.Job;
+import com.google.cloud.bigquery.Table;
+import com.google.cloud.bigquery.TableId;
+import org.threeten.bp.Duration;
+
+public class ExtractTableToJson {
+
+  public static void runExtractTableToJson() {
+    // TODO(developer): Replace these variables before running the sample.
+    String projectId = "bigquery-public-data";
+    String datasetName = "samples";
+    String tableName = "shakespeare";
+    String bucketName = "my-bucket";
+    String destinationUri = "gs://" + bucketName + "/path/to/file";
+    // For more information on export formats available see:
+    // https://cloud.google.com/bigquery/docs/exporting-data#export_formats_and_compression_types
+    // For more information on Job see:
+    // https://googleapis.dev/java/google-cloud-clients/latest/index.html?com/google/cloud/bigquery/package-summary.html
+
+    // Note that FormatOptions.json().toString() is not "JSON" but "NEWLINE_DELIMITED_JSON"
+    // Using FormatOptions Enum for this will prevent problems with unexpected format names.
+    String dataFormat = FormatOptions.json().toString();
+
+    extractTableToJson(projectId, datasetName, tableName, destinationUri, dataFormat);
+  }
+
+  // Exports datasetName:tableName to destinationUri as a JSON file
+  public static void extractTableToJson(
+      String projectId, String datasetName, String tableName, String destinationUri,
+      String dataFormat) {
+    try {
+      // Initialize client that will be used to send requests. This client only needs to be created
+      // once, and can be reused for multiple requests.
+      BigQuery bigquery = BigQueryOptions.getDefaultInstance().getService();
+
+      TableId tableId = TableId.of(projectId, datasetName, tableName);
+      Table table = bigquery.getTable(tableId);
+
+      Job job = table.extract(dataFormat, destinationUri);
+
+      // Blocks until this job completes its execution, either failing or succeeding.
+      Job completedJob =
+          job.waitFor(
+              RetryOption.initialRetryDelay(Duration.ofSeconds(1)),
+              RetryOption.totalTimeout(Duration.ofMinutes(3)));
+      if (completedJob == null) {
+        System.out.println("Job not executed since it no longer exists.");
+        return;
+      } else if (completedJob.getStatus().getError() != null) {
+        System.out.println(
+            "BigQuery was unable to extract due to an error: \n" + job.getStatus().getError());
+        return;
+      }
+      System.out.println("Table export successful. Check in GCS bucket for the " +
+          dataFormat + " file.");
+    } catch (BigQueryException | InterruptedException e) {
+      System.out.println("Table extraction job was interrupted. \n" + e.toString());
+    }
+  }
+}
+// [END bigquery_extract_table_json]

samples/snippets/src/test/java/com/example/bigquery/ExtractTableToJsonIT.java

@@ -0,0 +1,74 @@
+/*
+ * Copyright 2020 Google LLC
+ *
+ * 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.bigquery;
+
+import static com.google.common.truth.Truth.assertThat;
+import static junit.framework.TestCase.assertNotNull;
+
+import com.google.cloud.bigquery.FormatOptions;
+import java.io.ByteArrayOutputStream;
+import java.io.PrintStream;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+public class ExtractTableToJsonIT {
+  private ByteArrayOutputStream bout;
+  private PrintStream out;
+
+  private static final String GCS_BUCKET = System.getenv("GCS_BUCKET");
+
+  private static void requireEnvVar(String varName) {
+    assertNotNull(
+        "Environment variable " + varName + " is required to perform these tests.",
+        System.getenv(varName));
+  }
+
+  @BeforeClass
+  public static void checkRequirements() {
+    requireEnvVar("GCS_BUCKET");
+  }
+
+  @Before
+  public void setUp() throws Exception {
+    bout = new ByteArrayOutputStream();
+    out = new PrintStream(bout);
+    System.setOut(out);
+  }
+
+  @After
+  public void tearDown() {
+    System.setOut(null);
+  }
+
+  @Test
+  public void testExtractTableToJson() {
+    String projectId = "bigquery-public-data";
+    String datasetName = "samples";
+    String tableName = "shakespeare";
+    String destinationUri = "gs://" + GCS_BUCKET + "/extractTest.json";
+    // FormatOptions.json() is not "JSON" but "NEWLINE_DELIMITED_JSON"
+    String dataFormat = FormatOptions.json().toString();
+
+    // Extract table content to GCS in JSON format
+    ExtractTableToJson.extractTableToJson(projectId, datasetName, tableName, destinationUri,
+            dataFormat);
+    assertThat(bout.toString())
+        .contains("Table export successful. Check in GCS bucket for the " + dataFormat + " file.");
+  }
+}