在這篇文章內容，將會學到如何使用HBase Client API對HBase的CRUD操作。本篇的範例程式碼所使用的HBase版本是 HBase 0.98.x ，相容於 HBase 1.x.x 。
首先先來看一下SQL、API與HBase Shell的CRUD對照：
| SQL | HBase Client API | HBase Shell |
|---|---|---|
| select | Get/Scan | get/scan |
| insert | Put | put |
| delete | Delete | delete |
| update | Put | get/scan |
HBase Connection
與所有RDB相同，連線到HBase也需要設定connection：
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.HBaseConfiguration;
import org.apache.hadoop.hbase.client.HBaseAdmin;
import org.apache.hadoop.hbase.client.HTable;
Configuration conf = HBaseConfiguration.create();
conf.set("hbase.zookeeper.quorum", "localhost");
conf.set("hbase.zookeeper.property.clientPort", “2181");
HBaseAdmin admin = new HBaseAdmin(conf);
String tableName = "employees";
HTable table = new HTable(conf, tableName);
使用Put新增一筆(row)資料
String tableName = "employees";
HTable htable = new HTable(conf, tableName);
Put put = new Put(Bytes.toBytes("Development_999999"));
byte[] familyName = Bytes.toBytes("cf1");
String[] columnNames = new String[] { "p-birth_date", "p-first_name",
"p-last_name","p-gender", "p-hire_date", "d-from_date", "d-to_date" };
String[] values = new String[] { "1970-03-10", "John", "Li", "M", "1988-05-08", "1988-05-08", "9999-01-01" };
put.add(familyName, Bytes.toBytes(columnNames[0]), Bytes.toBytes( toDateValue(values[0]) ));
put.add(familyName, Bytes.toBytes(columnNames[1]), Bytes.toBytes( values[1] ));
put.add(familyName, Bytes.toBytes(columnNames[2]), Bytes.toBytes( values[2] ));
put.add(familyName, Bytes.toBytes(columnNames[3]), Bytes.toBytes( values[3] ));
put.add(familyName, Bytes.toBytes(columnNames[4]), Bytes.toBytes( toDateValue(values[4]) ));
put.add(familyName, Bytes.toBytes(columnNames[5]), Bytes.toBytes( toDateValue(values[5]) ));
put.add(familyName, Bytes.toBytes(columnNames[6]), Bytes.toBytes( toDateValue(values[6]) ));
htable.put(put);
htable.close();
使用Get查詢一筆(row)資料
現在我們來查剛剛Put進去的資料。
String tableName = "employees";
HTable htable = new HTable(conf, tableName);
Get get = new Get(Bytes.toBytes("Development_999999"));
Result result = htable.get(get);
System.out.println( "result size: " + result.size() );
System.out.println( "result string: " + result.toString() );
for (int i=0; i<result.size(); i++) {
System.out.println( String.format("result[%d]: %s", i, result.raw()[i].toString()));
}
htable.close();
使用Scan來查詢table所有資料
String tableName = "employees";
HTable htable = new HTable(conf, tableName);
Scan scan = new Scan();
ResultScanner scanner = htable.getScanner(scan);
for (Result res : scanner) {
System.out.println(res);
}
scanner.close();
htable.close();
使用Delete刪除一筆資料
String tableName = "employees";
HTable htable = new HTable(conf, tableName);
Delete delete = new Delete(Bytes.toBytes("Development_999999"));
htable.delete(delete);
htable.close();
最後
看完了Hello World版本的API後，接下來要介紹如何使用HBase Bolk-Load。