Apache HBase APIs

本章提供HBase本地api接口的相关操作。这里信息不过详细，只提供了API的快速参考。本章的例子是不完整的，只是为了举例而用。

75.example

Example 40. Create, modify and delete a Table Using Java

package com.example.hbase.admin;
import java.io.IOException;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.hbase.HBaseConfiguration;
import org.apache.hadoop.hbase.HColumnDescriptor;
import org.apache.hadoop.hbase.HConstants;
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.ConnectionFactory;
import org.apache.hadoop.hbase.io.compress.Compression.Algorithm;
public class Example {
    private static final String TABLE_NAME = "MY_TABLE_NAME_TOO";
    private static final String CF_DEFAULT = "DEFAULT_COLUMN_FAMILY";
    public static void createOrOverwrite(Admin admin, HTableDescriptor table) throws IOException {
    if (admin.tableExists(table.getTableName())) {
        admin.disableTable(table.getTableName());
        admin.deleteTable(table.getTableName());
    }
    admin.createTable(table);
    }
    public static void createSchemaTables(Configuration config) throws IOException {
    try (Connection connection = ConnectionFactory.createConnection(config);
     Admin admin = connection.getAdmin()) {
        HTableDescriptor table = new HTableDescriptor(TableName.valueOf(TABLE_NAME));
        table.addFamily(new HColumnDescriptor(CF_DEFAULT).setCompressionType(Algorithm.NONE));
        System.out.print("Creating table. ");
        createOrOverwrite(admin, table);
        System.out.println(" Done.");
    }
    }
    public static void modifySchema (Configuration config) throws IOException {
    try (Connection connection = ConnectionFactory.createConnection(config);
     Admin admin = connection.getAdmin()) {
      TableName tableName = TableName.valueOf(TABLE_NAME);
      if (!admin.tableExists(tableName)) {
      System.out.println("Table does not exist.");
      System.exit(-1);
    }
    HTableDescriptor table = admin.getTableDescripto(tableName);
      // 更新存在的表格
    HColumnDescriptor newColumn = new HColumnDescriptor("NEWCF");
    newColumn.setCompactionCompressionType(Algorithm.GZ);
    newColumn.setMaxVersions(HConstants.ALL_VERSIONS);
    admin.addColumn(tableName, newColumn);
      // 更新列族
      HColumnDescriptor existingColumn = new HColumnDescriptor(CF_DEFAULT);
      existingColumn.setCompactionCompressionType(Algorithm.GZ);
      existingColumn.setMaxVersions(HConstants.ALL_VERSIONS);
      table.modifyFamily(existingColumn);
      admin.modifyTable(tableName, table);
      // disable存在表
      admin.disableTable(tableName);
      //删除存在的列族
      admin.deleteColumn(tableName, CF_DEFAULT.getBytes("UTF-8"));
      // Delete a table (Need to be disabled first)
      admin.deleteTable(tableName);
  }
  }
    public static void main(String... args) throws IOException {
      Configuration config = HBaseConfiguration.create();
      //增加必要的配置文件(hbase-site.xml, core-site.xml)
      config.addResource(new Path(System.getenv("HBASE_CONF_DIR"), "hbase-site.xml"));
      config.addResource(new Path(System.getenv("HADOOP_CONF_DIR"), "core-site.xml"));
      createSchemaTables(config);
      modifySchema(config);
  }
}