Ejemplo: Aplicación Hello World con las API de HBase para Java

En este ejemplo, se usa una aplicación muy simple llamada Hello World, que usa la biblioteca cliente HBase de Cloud Bigtable, y se muestra cómo realizar las siguientes acciones:

• Conectarse a una instancia de Cloud Bigtable
• Crear una tabla nueva
• Escribir datos en la tabla
• Volver a leer datos
• Borrar la tabla

Ejecuta la muestra

En esta muestra, se usan las API de HBase para comunicarse con Cloud Bigtable. El código para esta muestra se encuentra en el repositorio de GitHub GoogleCloudPlatform/cloud-bigtable-examples, en el directorio java/hello-world.

Para ejecutar este programa de muestra, sigue las instrucciones de la muestra en GitHub.

Cómo usar las API de HBase

La aplicación de muestra se conecta con Bigtable y demuestra algunas operaciones simples.

Cómo instalar e importar la biblioteca cliente

En esta muestra, se usa el cliente de HBase de Cloud Bigtable para Java y Maven. Consulta las instrucciones para usar la biblioteca cliente.

En esta muestra, se usan las siguientes importaciones:

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

Ver en GitHub

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

Conéctate a Bigtable

Conéctate con Cloud Bigtable mediante la clase BigtableConfiguration.

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

Ver en GitHub

// 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();

Crear una tabla

Usa la API de Administrador para crear una tabla.

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

Ver en GitHub

// 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);

Escribe filas en una tabla

Usa la clase Table para agregar filas a la tabla. Para obtener una mejor capacidad de procesamiento, considera usar la clase BigtableBufferedMutator.

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

Ver en GitHub

// 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);
}

Leer una fila por su clave

Obtén una fila directamente con su clave.

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

Ver en GitHub

// 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);

Analiza todas las filas de una tabla

Usa la clase Scan para obtener un rango de filas.

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

Ver en GitHub

// 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));
}

Borrar una tabla

Borra una tabla con la API de Administrador.

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

Ver en GitHub

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

Revisión general

El ejemplo completo sin comentarios.

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

Ver en GitHub

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;
  }
}