docs: Expand hello world snippet to show how to access specific cells (#516)

* samples: Expand hello world snippet to show how to access specific cells by family & qualifier

* samples: Expand hello world snippet to show how to access specific cells by family & qualifier

Author: dmitry-fa

samples/snippets/src/main/java/com/m/examples/bigtable/HelloWorld.java

@@ -12,7 +12,7 @@
  * 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.m.examples.bigtable;
 
@@ -29,6 +29,8 @@
 import com.google.cloud.bigtable.data.v2.models.RowCell;
 import com.google.cloud.bigtable.data.v2.models.RowMutation;
 import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
 
 // [END bigtable_hw_imports_veneer]
 
@@ -48,7 +50,8 @@
 public class HelloWorld {
 
   private static final String COLUMN_FAMILY = "cf1";
-  private static final String COLUMN_QUALIFIER = "greeting";
+  private static final String COLUMN_QUALIFIER_GREETING = "greeting";
+  private static final String COLUMN_QUALIFIER_NAME = "name";
   private static final String ROW_KEY_PREFIX = "rowKey";
   private final String tableId;
   private final BigtableDataClient dataClient;
@@ -94,8 +97,13 @@ public void run() throws Exception {
     createTable();
     writeToTable();
     readSingleRow();
+    readSpecificCells();
     readTable();
     deleteTable();
+    close();
+  }
+
+  public void close() {
     dataClient.close();
     adminClient.close();
   }
@@ -119,13 +127,15 @@ public void writeToTable() {
     // [START bigtable_hw_write_rows_veneer]
     try {
       System.out.println("\nWriting some greetings to the table");
-      String[] greetings = {"Hello World!", "Hello Bigtable!", "Hello Java!"};
-      for (int i = 0; i < greetings.length; i++) {
+      String[] names = {"World", "Bigtable", "Java"};
+      for (int i = 0; i < names.length; i++) {
+        String greeting = "Hello " + names[i] + "!";
         RowMutation rowMutation =
             RowMutation.create(tableId, ROW_KEY_PREFIX + i)
-                .setCell(COLUMN_FAMILY, COLUMN_QUALIFIER, greetings[i]);
+                .setCell(COLUMN_FAMILY, COLUMN_QUALIFIER_NAME, names[i])
+                .setCell(COLUMN_FAMILY, COLUMN_QUALIFIER_GREETING, greeting);
         dataClient.mutateRow(rowMutation);
-        System.out.println(greetings[i]);
+        System.out.println(greeting);
       }
     } catch (NotFoundException e) {
       System.err.println("Failed to write to non-existent table: " + e.getMessage());
@@ -134,7 +144,7 @@ public void writeToTable() {
   }
 
   /** Demonstrates how to read a single row from a table. */
-  public void readSingleRow() {
+  public Row readSingleRow() {
     // [START bigtable_hw_get_by_key_veneer]
     try {
       System.out.println("\nReading a single row by row key");
@@ -145,29 +155,56 @@ public void readSingleRow() {
             "Family: %s    Qualifier: %s    Value: %s%n",
             cell.getFamily(), cell.getQualifier().toStringUtf8(), cell.getValue().toStringUtf8());
       }
+      return row;
+    } catch (NotFoundException e) {
+      System.err.println("Failed to read from a non-existent table: " + e.getMessage());
+      return null;
+    }
+    // [END bigtable_hw_get_by_key_veneer]
+  }
+
+  /** Demonstrates how to access specific cells by family and qualifier. */
+  public List<RowCell> readSpecificCells() {
+    // [START bigtable_hw_get_by_key_veneer]
+    try {
+      System.out.println("\nReading specific cells by family and qualifier");
+      Row row = dataClient.readRow(tableId, ROW_KEY_PREFIX + 0);
+      System.out.println("Row: " + row.getKey().toStringUtf8());
+      List<RowCell> cells = row.getCells(COLUMN_FAMILY, COLUMN_QUALIFIER_NAME);
+      for (RowCell cell : cells) {
+        System.out.printf(
+            "Family: %s    Qualifier: %s    Value: %s%n",
+            cell.getFamily(), cell.getQualifier().toStringUtf8(), cell.getValue().toStringUtf8());
+      }
+      return cells;
     } catch (NotFoundException e) {
       System.err.println("Failed to read from a non-existent table: " + e.getMessage());
+      return null;
     }
     // [END bigtable_hw_get_by_key_veneer]
   }
 
   /** Demonstrates how to read an entire table. */
-  public void readTable() {
+  public List<Row> readTable() {
     // [START bigtable_hw_scan_all_veneer]
     try {
       System.out.println("\nReading the entire table");
       Query query = Query.create(tableId);
       ServerStream<Row> rowStream = dataClient.readRows(query);
+      List<Row> tableRows = new ArrayList<>();
       for (Row r : rowStream) {
         System.out.println("Row Key: " + r.getKey().toStringUtf8());
+        tableRows.add(r);
         for (RowCell cell : r.getCells()) {
           System.out.printf(
               "Family: %s    Qualifier: %s    Value: %s%n",
               cell.getFamily(), cell.getQualifier().toStringUtf8(), cell.getValue().toStringUtf8());
         }
       }
+      return tableRows;
     } catch (NotFoundException e) {
       System.err.println("Failed to read a non-existent table: " + e.getMessage());
+      return null;
     }
     // [END bigtable_hw_scan_all_veneer]
   }

samples/snippets/src/test/java/com/m/examples/bigtable/HelloWorldTest.java

@@ -12,27 +12,27 @@
  * 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.m.examples.bigtable;
 
+import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertTrue;
 
 import com.google.cloud.bigtable.admin.v2.BigtableTableAdminClient;
 import com.google.cloud.bigtable.admin.v2.BigtableTableAdminSettings;
 import com.google.cloud.bigtable.admin.v2.models.CreateTableRequest;
 import com.google.cloud.bigtable.data.v2.BigtableDataClient;
 import com.google.cloud.bigtable.data.v2.BigtableDataSettings;
-import com.google.cloud.bigtable.data.v2.models.Row;
 import java.io.IOException;
 import java.util.Random;
 import java.util.concurrent.TimeUnit;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 import org.junit.After;
 import org.junit.AfterClass;
-import org.junit.AssumptionViolatedException;
 import org.junit.Before;
 import org.junit.BeforeClass;
 import org.junit.Test;
@@ -86,10 +86,11 @@ public void setup() throws IOException {
   }
 
   @After
-  public void after() {
+  public void teardown() {
     if (adminClient.exists(tableId)) {
       adminClient.deleteTable(tableId);
     }
+    helloWorld.close();
   }
 
   @Test
@@ -103,18 +104,26 @@ public void testCreateAndDeleteTable() throws IOException {
     // Deletes a table.
     testHelloWorld.deleteTable();
     assertTrue(!adminClient.exists(testTable));
+    testHelloWorld.close();
   }
 
   @Test
   public void testWriteToTable() {
     // Writes to a table.
+    assertNull(dataClient.readRow(tableId, "rowKey0"));
     helloWorld.writeToTable();
-    Row row = dataClient.readRow(tableId, "rowKey0");
-    assertNotNull(row);
+    assertNotNull(dataClient.readRow(tableId, "rowKey0"));
   }
 
-  // TODO: add test for helloWorld.readSingleRow()
-  // TODO: add test for helloWorld.readTable()
+  @Test
+  public void testReads() {
+    assertEquals(0, helloWorld.readTable().size());
+    helloWorld.writeToTable();
+
+    assertEquals(2, helloWorld.readSingleRow().getCells().size());
+    assertEquals(1, helloWorld.readSpecificCells().size());
+    assertEquals(3, helloWorld.readTable().size());
+  }
 
   @Test
   public void testRunDoesNotFail() throws Exception {