scan 命令用于查看HTable数据。使用 scan 命令可以得到表中的数据。它的语法如下：
| scan ‘<table name>’ |
下面的示例演示了如何使用scan命令从表中读取数据。在这里读取的是emp表。
| hbase(main):010:0> scan 'emp' |
| ROW COLUMN+CELL |
| 1 column=personal data:city, timestamp=1417521848375, value=hyderabad |
| 1 column=personal data:name, timestamp=1417521785385, value=ramu |
| 1 column=professional data:designation, timestamp=1417585277,value=manager |
| 1 column=professional data:salary, timestamp=1417521903862, value=50000 |
| 1 row(s) in 0.0370 seconds |
使用Java API扫描整个表的数据的完整程序如下：
| import java.io.IOException; |
| import org.apache.hadoop.conf.Configuration; |
| import org.apache.hadoop.hbase.HBaseConfiguration; |
| import org.apache.hadoop.hbase.util.Bytes; |
| import org.apache.hadoop.hbase.client.HTable; |
| import org.apache.hadoop.hbase.client.Result; |
| import org.apache.hadoop.hbase.client.ResultScanner; |
| import org.apache.hadoop.hbase.client.Scan; |
| public class ScanTable{ |
| public static void main(String args[]) throws IOException{ |
| // Instantiating Configuration class |
| Configuration config = HBaseConfiguration.create(); |
| // Instantiating HTable class |
| HTable table = new HTable(config, "emp"); |
| // Instantiating the Scan class |
| Scan scan = new Scan(); |
| // Scanning the required columns |
| scan.addColumn(Bytes.toBytes("personal"), Bytes.toBytes("name")); |
| scan.addColumn(Bytes.toBytes("personal"), Bytes.toBytes("city")); |
| // Getting the scan result |
| ResultScanner scanner = table.getScanner(scan); |
| // Reading values from scan result |
| for (Result result = scanner.next(); result != null; result = Scanner.next()) |
| System.out.println("Found row : " + result); |
| //closing the scanner |
| scanner.close(); |
| } |
| } |
| $javac ScanTable.java |
| $java ScanTable |
下面列出的是输出：
| Found row : |
| keyvalues={row1/personal:city/1418275612888/Put/vlen=5/mvcc=0, |
| row1/personal:name/1418035791555/Put/vlen=4/mvcc=0} |
