Add a simple java Hello World application using HBase API

Author: garye

bigtable/hbase/snippets/src/main/java/com/example/cloud/bigtable/helloworld/HelloWorld.java

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+/**
+ * Copyright 2016 Google Inc. All Rights Reserved.
+ *
+ * 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 com.example.cloud.bigtable.helloworld;
+
+import com.google.cloud.bigtable.hbase.BigtableConfiguration;
+
+import org.apache.hadoop.hbase.HColumnDescriptor;
+import org.apache.hadoop.hbase.HTableDescriptor;
+import org.apache.hadoop.hbase.TableName;
+import org.apache.hadoop.hbase.client.Admin;
+import org.apache.hadoop.hbase.client.Connection;
+import org.apache.hadoop.hbase.client.Get;
+import org.apache.hadoop.hbase.client.Put;
+import org.apache.hadoop.hbase.client.Result;
+import org.apache.hadoop.hbase.client.ResultScanner;
+import org.apache.hadoop.hbase.client.Scan;
+import org.apache.hadoop.hbase.client.Table;
+import org.apache.hadoop.hbase.util.Bytes;
+
+import java.io.IOException;
+
+/**
+ * A minimal application that connects to Cloud Bigtable using the native HBase API
+ * and performs some basic operations.
+ */
+public class HelloWorld {
+
+  // Refer to table metadata names by byte array in the HBase API
+  private static final byte[] TABLE_NAME = Bytes.toBytes("Hello-Bigtable");
+  private static final byte[] COLUMN_FAMILY_NAME = Bytes.toBytes("cf1");
+  private static final byte[] COLUMN_NAME = Bytes.toBytes("greeting");
+
+  // Write some friendly greetings to Cloud Bigtable
+  private static final String[] GREETINGS =
+      { "Hello World!", "Hello Cloud Bigtable!", "Hello HBase!" };
+
+  /**
+   * Connects to Cloud Bigtable, runs some basic operations and prints the results
+   */
+  private static void doHelloWorld(String projectId, String zone, String clusterId) {
+
+    // Create the Bigtable connection, use try-with-resources to make sure it gets closed
+    try (Connection connection = BigtableConfiguration.connect(projectId, zone, clusterId)) {
+
+      // The admin API lets us create, manage and delete tables
+      Admin admin = connection.getAdmin();
+
+      // Create a table with a single column family
+      HTableDescriptor descriptor = new HTableDescriptor(TableName.valueOf(TABLE_NAME));
+      descriptor.addFamily(new HColumnDescriptor(COLUMN_FAMILY_NAME));
+
+      print("Create table " + descriptor.getNameAsString());
+      admin.createTable(descriptor);
+
+      // Retrieve the table we just created so we can do some reads and writes
+      Table table = connection.getTable(TableName.valueOf(TABLE_NAME));
+
+      // Write some rows to the table
+      print("Write some greetings to the table");
+      for (int i = 0; i < GREETINGS.length; i++) {
+        // Each row has a unique row key
+        String rowKey = "greeting" + i;
+
+        // Put a single row into the table. We could also pass a list of Puts to write a batch.
+        Put put = new Put(Bytes.toBytes(rowKey));
+        put.addColumn(COLUMN_FAMILY_NAME, COLUMN_NAME, Bytes.toBytes(GREETINGS[i]));
+        table.put(put);
+      }
+
+      // Get the first greeting by row key
+      String rowKey = "greeting0";
+      Result getResult = table.get(new Get(Bytes.toBytes(rowKey)));
+      String greeting = Bytes.toString(getResult.getValue(COLUMN_FAMILY_NAME, COLUMN_NAME));
+      System.out.println(
+          String.format("Get a single greeting by row key: %s = %s", rowKey, greeting));
+
+      // Now scan across all rows.
+      Scan scan = new Scan();
+
+      print("Scan for all greetings:");
+      ResultScanner scanner = table.getScanner(scan);
+      for (Result row : scanner) {
+        byte[] valueBytes = row.getValue(COLUMN_FAMILY_NAME, COLUMN_NAME);
+        System.out.println('\t' + Bytes.toString(valueBytes));
+      }
+
+      // Clean up by disabling and then deleting the table
+      print("Delete the table");
+      admin.disableTable(table.getName());
+      admin.deleteTable(table.getName());
+
+    } catch (IOException e) {
+      System.err.println("Exception while running HelloWorld: " + e.getMessage());
+      e.printStackTrace();
+      System.exit(1);
+    }
+
+    System.exit(0);
+  }
+
+  private static void print(String msg) {
+    System.out.println("HelloWorld: " + msg);
+  }
+
+  public static void main(String[] args) {
+    if (args.length < 3) {
+      System.err.println("Usage: HelloWorld <projectId> <zone> <clusterId>");
+      System.exit(1);
+    }
+
+    doHelloWorld(args[0], args[1], args[2]);
+  }
+
+}