Java hello world 的 HBase API

這個範例是一個「hello world」應用程式，使用 Java 適用的 Bigtable HBase 用戶端程式庫，為您說明如何執行以下作業：

  • 設定驗證方法
  • 連線至 Bigtable 執行個體。
  • 建立新的資料表。
  • 將資料寫入資料表。
  • 讀取資料。
  • 刪除資料表。

設定驗證方法

如要在本機開發環境中使用本頁的 Java 範例，請安裝並初始化 gcloud CLI，然後使用使用者憑證設定應用程式預設憑證。

  1. Install the Google Cloud CLI.

  2. If you're using an external identity provider (IdP), you must first sign in to the gcloud CLI with your federated identity.

  3. To initialize the gcloud CLI, run the following command: 

    gcloud init

  4. If you're using a local shell, then create local authentication credentials for your user account: 

    gcloud auth application-default login

    You don't need to do this if you're using Cloud Shell.

    If an authentication error is returned, and you are using an external identity provider (IdP), confirm that you have signed in to the gcloud CLI with your federated identity.

詳情請參閱 Set up authentication for a local development environment。

執行範例

本範例使用 HBase API 與 Bigtable 通訊。您可以在 GitHub 存放區 GoogleCloudPlatform/cloud-bigtable-examples 的 java/hello-world 目錄中找到本範例的程式碼。

如要執行這個範例程式，請依照 GitHub 網頁上的說明操作。

使用 HBase API

這個應用程式範例會連線至 Bigtable，示範部分簡易作業。

安裝及匯入用戶端程式庫

本範例使用 Java 適用的 Bigtable HBase 用戶端和 Maven。請參閱使用用戶端程式庫的操作說明。

下面列出了這個範例所匯入的程式庫：

import com.google.cloud.bigtable.hbase.BigtableConfiguration;
import java.io.IOException;

連線至 Bigtable

使用 BigtableConfiguration 類別連線至 Bigtable。

// Create the Bigtable connection, use try-with-resources to make sure it gets closed
try (Connection connection = BigtableConfiguration.connect(projectId, instanceId)) {

  // The admin API lets us create, manage and delete tables
  Admin admin = connection.getAdmin();

建立資料表

使用 Admin API 建立資料表。

// Create a table with a single column family
HTableDescriptor descriptor = new HTableDescriptor(TableName.valueOf(TABLE_NAME));
descriptor.addFamily(new HColumnDescriptor(COLUMN_FAMILY_NAME));

System.out.println("HelloWorld: Create table " + descriptor.getNameAsString());
admin.createTable(descriptor);

將資料列寫入資料表

使用 Table 類別將資料列放入資料表。如要提升總處理量，建議使用 BigtableBufferedMutator 類別。

// 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
System.out.println("HelloWorld: Write some greetings to the table");
for (int i = 0; i < GREETINGS.length; i++) {
  // Each row has a unique row key.
  //
  // Note: This example uses sequential numeric IDs for simplicity, but
  // this can result in poor performance in a production application.
  // Since rows are stored in sorted order by key, sequential keys can
  // result in poor distribution of operations across nodes.
  //
  // For more information about how to design a Bigtable schema for the
  // best performance, see the documentation:
  //
  //     https://cloud.google.com/bigtable/docs/schema-design
  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);
}

依索引鍵讀取資料列

直接使用資料列的索引鍵來擷取資料列。

// 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("Get a single greeting by row key");
System.out.printf("\t%s = %s\n", rowKey, greeting);

掃描所有資料表資料列

使用 Scan 類別擷取特定範圍的資料列。

// Now scan across all rows.
Scan scan = new Scan();

System.out.println("HelloWorld: 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));
}

刪除資料表

使用 Admin API 刪除資料表。

// Clean up by disabling and then deleting the table
System.out.println("HelloWorld: Delete the table");
admin.disableTable(table.getName());
admin.deleteTable(table.getName());

全面整合使用

以下是沒有註解的完整範例。


package com.example.bigtable;

import com.google.cloud.bigtable.hbase.BigtableConfiguration;
import java.io.IOException;
import java.util.UUID;
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;

public class HelloWorld {

  private static final byte[] TABLE_NAME =
      Bytes.toBytes("Hello-Bigtable-" + UUID.randomUUID().toString().substring(0, 19));
  private static final byte[] COLUMN_FAMILY_NAME = Bytes.toBytes("cf1");
  private static final byte[] COLUMN_NAME = Bytes.toBytes("greeting");

  private static final String[] GREETINGS = {
    "Hello World!", "Hello Cloud Bigtable!", "Hello HBase!"
  };

  protected static void doHelloWorld(String projectId, String instanceId) {

    try (Connection connection = BigtableConfiguration.connect(projectId, instanceId)) {

      Admin admin = connection.getAdmin();

      try {
        HTableDescriptor descriptor = new HTableDescriptor(TableName.valueOf(TABLE_NAME));
        descriptor.addFamily(new HColumnDescriptor(COLUMN_FAMILY_NAME));

        System.out.println("HelloWorld: Create table " + descriptor.getNameAsString());
        admin.createTable(descriptor);

        Table table = connection.getTable(TableName.valueOf(TABLE_NAME));

        System.out.println("HelloWorld: Write some greetings to the table");
        for (int i = 0; i < GREETINGS.length; i++) {
          String rowKey = "greeting" + i;

          Put put = new Put(Bytes.toBytes(rowKey));
          put.addColumn(COLUMN_FAMILY_NAME, COLUMN_NAME, Bytes.toBytes(GREETINGS[i]));
          table.put(put);
        }

        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("Get a single greeting by row key");
        System.out.printf("\t%s = %s\n", rowKey, greeting);

        Scan scan = new Scan();

        System.out.println("HelloWorld: 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));
        }

        System.out.println("HelloWorld: Delete the table");
        admin.disableTable(table.getName());
        admin.deleteTable(table.getName());
      } catch (IOException e) {
        if (admin.tableExists(TableName.valueOf(TABLE_NAME))) {
          System.out.println("HelloWorld: Cleaning up table");
          admin.disableTable(TableName.valueOf(TABLE_NAME));
          admin.deleteTable(TableName.valueOf(TABLE_NAME));
        }
        throw e;
      }
    } catch (IOException e) {
      System.err.println("Exception while running HelloWorld: " + e.getMessage());
      e.printStackTrace();
    }
  }

  public static void main(String[] args) {
    String projectId = requiredProperty("bigtable.projectID");
    String instanceId = requiredProperty("bigtable.instanceID");

    doHelloWorld(projectId, instanceId);
  }

  private static String requiredProperty(String prop) {
    String value = System.getProperty(prop);
    if (value == null) {
      throw new IllegalArgumentException("Missing required system property: " + prop);
    }
    return value;
  }
}