Hbase之必要时取出请求的行(列族所有数据)
import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.hbase.CellScanner; import org.apache.hadoop.hbase.HBaseConfiguration; import org.apache.hadoop.hbase.TableName; import org.apache.hadoop.hbase.client.*; import org.apache.hadoop.hbase.util.Bytes; import java.io.IOException; /** * Created by similarface on 16/8/22. */ public class RetrievesRequestedRowNecessary { public static void main(String args[]) throws IOException { Configuration configuration = HBaseConfiguration.create(); Connection connection = ConnectionFactory.createConnection(configuration); //建立表的连接 Table table = connection.getTable(TableName.valueOf("testtable")); //获取行键 企图获取一个不存在的行 Get get1 = new Get(Bytes.toBytes("95599")); //添加查询的列族和列限定符号 get1.addColumn(Bytes.toBytes("colfam1"), Bytes.toBytes("qual1")); //获取结果级 Result result1 = table.get(get1); //结果集是否为空 ==> Get 1 isEmpty: true System.out.println("Get 1 isEmpty: " + result1.isEmpty()); //根据result获取游标 CellScanner scanner1 = result1.cellScanner(); //循环遍历结果集的数据 当然是没有任何数据 while (scanner1.advance()) { System.out.println("Get 1 Cell: " + scanner1.current()); } //95599行键的值 数据库不存在这行数据 Get get2 = new Get(Bytes.toBytes("95599")); //指定列族和列限定符 get2.addColumn(Bytes.toBytes("colfam1"), Bytes.toBytes("qual1")); //95599这行是在数据库中没有的 setClosestRowBefore 会试图去取前面的行如果有必要的话 get2.setClosestRowBefore(true); //获取数据集 ==> Get 2 isEmpty: false Result result2 = table.get(get2); System.out.println("Get 2 isEmpty: " + result2.isEmpty()); //继续获取游标 CellScanner scanner2 = result2.cellScanner(); //遍历游标获取数据 ==> Get 2 Cell: 10086/colfam1:qual1/1471836722159/Put/vlen=12/seqid=0 while (scanner2.advance()) { System.out.println("Get 2 Cell: " + scanner2.current()); } //这行数据库是存在的 Get get3 = new Get(Bytes.toBytes("10010")); get3.addColumn(Bytes.toBytes("colfam1"), Bytes.toBytes("qual2")); //依然+了setClosestRowBefore get3.setClosestRowBefore(true); // ==> Get 3 isEmpty: false Result result3 = table.get(get3); System.out.println("Get 3 isEmpty: " + result3.isEmpty()); CellScanner scanner3 = result3.cellScanner(); //如果存在行还是取出的该行的数据 while (scanner3.advance()) { //叫了setClosestRowBefore 的作用在这儿是请求列族中的所有列分隔的字段都要取出来 // Get 3 Cell: 10010/colfam1:qual1/1471836722159/Put/vlen=12/seqid=0 // Get 3 Cell: 10010/colfam1:qual2/1471836722159/Put/vlen=18/seqid=0 System.out.println("Get 3 Cell: " + scanner3.current()); } Get get4 = new Get(Bytes.toBytes("10086")); get4.addColumn(Bytes.toBytes("colfam1"), Bytes.toBytes("qual1")); //Get 4 isEmpty: false Result result4 = table.get(get4); System.out.println("Get 4 isEmpty: " + result4.isEmpty()); CellScanner scanner4 = result4.cellScanner(); while (scanner4.advance()) { //Get 4 Cell: 10086/colfam1:qual1/1471836722159/Put/vlen=12/seqid=0 System.out.println("Get 4 Cell: " + scanner4.current()); } } } /** Get 1 isEmpty: false Get 1 Cell: 10086/colfam1:qual1/1471836722159/Put/vlen=12/seqid=0 Get 2 isEmpty: false Get 2 Cell: 10086/colfam1:qual1/1471836722159/Put/vlen=12/seqid=0 Get 3 isEmpty: false Get 3 Cell: 10010/colfam1:qual1/1471836722159/Put/vlen=12/seqid=0 Get 3 Cell: 10010/colfam1:qual2/1471836722159/Put/vlen=18/seqid=0 Get 4 isEmpty: false Get 4 Cell: 10086/colfam1:qual1/1471836722159/Put/vlen=12/seqid=0 **/