source: sample/hadoop-0.17/tw/org/nchc/code/HBaseClient.java @ 20

/**
 * Program: HBaseClient.java
 * Editor: Waue Chen 
 * From :  NCHC. Taiwn
 * Last Update Date: 06/10/2008
 */

package tw.org.nchc.code;

import java.io.IOException;
import java.util.SortedMap;
import java.util.TreeMap;

import org.apache.hadoop.hbase.HBaseConfiguration;
import org.apache.hadoop.hbase.HScannerInterface;
import org.apache.hadoop.hbase.HStoreKey;
import org.apache.hadoop.hbase.HTable;
import org.apache.hadoop.io.Text;

/**
 * Demo that illustrates the HBase client API.
 * The demo program will insert values to " Column Family: Column qualifier" and then print these.
 *  pre-do : create a hbase table "test_table" with (CF:CI) which (" column family ", " column qualifier ")
 *  1. $ bin/hbase shell
 *  2. > create table test_table("CF");
 *  ok ! we can test it  
 *  3. > insert into test_table("CF:CI") values=("Hellow World") where row = "1";
 *  4. > select * from test_table; 

08/06/03 16:16:36 INFO hbase.HTable: Creating scanner over test_table starting at key 
+---------+-----------+-----------+
| Row                   | Column                  | Cell                     |
+---------+-----------+-----------+
| 1                        | CF:CI                     | Hellow World      |
+---------+-----------+-----------+
1 row(s) in set. (0.24 sec)

 *  on the  structure , "Row" means Row ID which is a key to describe a column;
 *  Column means the database structure in test_table, 
 *  Column Family , "CF",  should be defined while creating table.
 *  Column qualifier , "CI" , can be added dynamically.
 *  Cell is the value of CF:CI
 * 
 *  that's the structure; then the demo program will show you in console as below :
 *  
Illustration of adding data...
Writing row = 0, col 'CF:CI' = Hellow0
Writing row = 1, col 'CF:CI' = Hellow1
Writing row = 2, col 'CF:CI' = Hellow2
Writing row = 3, col 'CF:CI' = Hellow3
Writing row = 4, col 'CF:CI' = Hellow4
Writing row = 5, col 'CF:CI' = Hellow5
Writing row = 6, col 'CF:CI' = Hellow6
Writing row = 7, col 'CF:CI' = Hellow7
Writing row = 8, col 'CF:CI' = Hellow8
Writing row = 9, col 'CF:CI' = Hellow9

Illustration of querying...
row = 1, 'CF : CI ' = Hellow1

Illustration of scanning...
08/06/03 16:47:51 INFO hbase.HTable: Creating scanner over test_table starting at key 
row = 0//9223372036854775807, col 'CF:CI' = Hellow0
row = 1//9223372036854775807, col 'CF:CI' = Hellow1
row = 2//9223372036854775807, col 'CF:CI' = Hellow2
row = 3//9223372036854775807, col 'CF:CI' = Hellow3
row = 4//9223372036854775807, col 'CF:CI' = Hellow4
row = 5//9223372036854775807, col 'CF:CI' = Hellow5
row = 6//9223372036854775807, col 'CF:CI' = Hellow6
row = 7//9223372036854775807, col 'CF:CI' = Hellow7
row = 8//9223372036854775807, col 'CF:CI' = Hellow8
row = 9//9223372036854775807, col 'CF:CI' = Hellow9


 *  
 */
public class HBaseClient {

  public static void main(String[] args) throws IOException {

    // Open the "test_table" table. If it hasn't been in Hbase, you should create.
    HBaseConfiguration conf = new HBaseConfiguration();
    HTable table = new HTable(conf, new Text("test_table"));
  
    System.out.println("Illustration of adding data...");

    // create column formed  (Column Family:Column qualifier)
    Text column = new Text("CF:CI");

    // create row_id 
    Text row_id = new Text();

    // demo 1  : Insert ten demo values
    for (int i = 0; i < 10; i++) {
      
      // give row_id  value
      row_id.set(new Integer(i).toString());
      
      // let "indicate_id" indicate the column which row = row_id
      long indicate_id= table.startUpdate(row_id);
      
      //val =  value of CF:CI where row_id = i
      Text val = new Text("Hellow" + i);

      // put "val" to "column" from "table" where "row_id"
      // the same as :  
      // hql> INSERT INTO table( column ) VALUES=( val) WHERE ROW = row_id ;
      table.put(indicate_id, column, val.getBytes());
      table.commit(indicate_id);

      System.out.println("Writing row = " + row_id + ", col '" + column
          + "' = " + val);
    }

    // demo 2 : print column value only row = 1 ;
    System.out.println("\n Querying row = 1");
    
    // Get a single value for the specified row and column
    // byte[] = HTable.get(Text row, Text column)
    
    String s = Text.decode(table.get(new Text("1"),new Text("CF:CI")));
    // if change as  
    // String s = (table.get(new Text("1"),new Text("CF:CI"))).toString();
    // will get chaos code "  [B@1f14ceb"
    System.out.println("row = 1, 'CF : CI ' = " + s);

    // demo 3 :  Print the all contents of this table
    System.out.println("\nIllustration of scanning...");

    // we only want one column, but you can specify multiple columns to
    // fetch at once
    Text[] cols = { column };

    // Use HScannerInterface to crawl table
    HScannerInterface scanner = table.obtainScanner(cols, new Text());

    // column values are stored in a Map
    SortedMap<Text, byte[]> values = new TreeMap<Text, byte[]>();
    HStoreKey currentKey = new HStoreKey();
    while (scanner.next(currentKey, values)) {
      // decode the stored byte[] back into a String
      String val = Text.decode(values.get(column));
      System.out.println("row = " + currentKey + ", col '" + column + "' = "
          + val);
    }

    // remember to close scanner when done
    scanner.close();

  }

}