Simple Java API HBase manipulation
One of the ways to access HBase is through Java API. Here is the code for simple HBase manipulations like creating and changing a table, adding, retrieving and deleting data.
Contents
HOW TO
I used CDH 5.8.4 with Kerberos.
If you work with Maven there are 3 libraries that need to be imported:
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<dependency> <groupid>org.apache.hadoop</groupid> <artifactid>hadoop-common</artifactid> <version>2.6.0-cdh5.8.4</version> </dependency> <dependency> <groupid>org.apache.hbase</groupid> <artifactid>hbase-client</artifactid> <version>1.2.0-cdh5.8.4</version> </dependency> <dependency> <groupid>org.apache.hbase</groupid> <artifactid>hbase-common</artifactid> <version>1.2.0-cdh5.8.4</version> </dependency> |
Java Code
I assumed that the program is provided with name of the table to be created and manipulated.
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import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.hbase.*; import org.apache.hadoop.hbase.client.*; import org.apache.hadoop.hbase.io.compress.Compression; import org.apache.hadoop.hbase.util.Bytes; import java.io.IOException; import java.util.Arrays; import java.util.List; import java.util.stream.Collectors; public class HBaseManager { Connection connection; Admin admin; final static String DEFAULT_CF = "column_family1"; final static String NEW_CF = "column_family2"; public static void main(String args[]){ if (args.length < 1 || args[0] == null) { throw new IllegalArgumentException("no table name provided"); } String tableName = args[0]; HBaseManager hManager = new HBaseManager(); hManager.connect(); hManager.deleteTable(tableName); hManager.createTable(tableName); hManager.addColumnFamily(NEW_CF,tableName); hManager.addValue("row1",DEFAULT_CF,"column1","value1",tableName); hManager.addValue("row1",NEW_CF,"column2","value2",tableName); System.out.println(hManager.retrieveData("row1",NEW_CF,"column2", tableName)); System.out.println(hManager.retrieveData(tableName,1)); hManager.addValue("row2",DEFAULT_CF,"column1","value3",tableName); System.out.println(hManager.retrieveData(tableName,2)); hManager.closeCon(); } public Connection connect() { //initiating HBase connection Configuration conf = HBaseConfiguration.create(); try { connection = ConnectionFactory.createConnection(conf); admin = connection.getAdmin(); }catch(IOException e){ throw new RuntimeException("unable to connect to HBase ", e); } return connection; } public HTableDescriptor createTable(String tableName) { //HTableDescriptor contains the details about an HBase table such as //the descriptors of all the column families, is the table a catalog //table, hbase:meta, if the table is read only, the maximum size of //the memstore, when the region split should occur etc... HTableDescriptor table = new HTableDescriptor(TableName. valueOf(tableName)); table.addFamily(new HColumnDescriptor(DEFAULT_CF). setCompressionType(Compression.Algorithm.NONE)); try{ deleteTable(tableName); admin.createTable(table); }catch(IOException e){ throw new RuntimeException("unable to create HBase table ", e); } return table; } public void addColumnFamily(String columnName, String tableName) { //HColumnDescriptor contains information about a column family such as // the number of versions, compression settings, etc. It is used as an // input when creating a table or adding a column. HColumnDescriptor newColumn = new HColumnDescriptor(columnName); newColumn.setCompressionType(Compression.Algorithm.NONE); try { admin.addColumn(TableName.valueOf(tableName),newColumn); }catch(IOException e){ throw new RuntimeException("unable to add a column to HBase table " + tableName, e); } } public void addValue(String rowKey, String columnFamily, String columnName, String value, String tableName) { //Cell describes the values associated with row, column family and // qualifier. Put object is used for adding new records. Cell cell = CellUtil.createCell(Bytes.toBytes(rowKey), Bytes.toBytes(columnFamily), Bytes.toBytes(columnName), 201707091000L, (byte)4, Bytes.toBytes(value)); try (Table table = connection.getTable(TableName.valueOf(tableName))){ //Table can be used to get, put, delete or scan data from a table. Put p = new Put(Bytes.toBytes(rowKey)); p.add(cell); table.put(p); }catch(IOException e){ throw new RuntimeException("unable to add data to HBase table ", e); } } //retrieve the value public String retrieveData(String rowKey, String columnFamily, String columnName, String tableName) { Cell val = null; try (Table table = connection.getTable(TableName.valueOf(tableName))){ Get g = new Get(Bytes.toBytes(rowKey)); Result result = table.get(g); if (result != null) { val= result.getColumnLatestCell(Bytes.toBytes(columnFamily) Bytes.toBytes(columnName)); } }catch(IOException e){ throw new RuntimeException("unable to retrieve the data from HBase table ", e); } return Bytes.toString(CellUtil.cloneValue(val)); } //retrieve the whole data row public List<String> retrieveData(String rowKey, String tableName) { List<String> cellValues; try (Table table = connection.getTable(TableName.valueOf(tableName))){ Get g = new Get(Bytes.toBytes(rowKey)); Result result = table.get(g); cellValues = result.listCells().stream().map(CellUtil::cloneValue). map(Bytes::toString).collect(Collectors.toList()); }catch(IOException e){ throw new RuntimeException("unable to retrieve the data from HBase table ", e); } return cellValues; } //retrieve data from few rows public List<String> retrieveData(String tableName, Integer numRows) { List<String> cellValues; try (Table table = connection.getTable(TableName.valueOf(tableName))){ Scan scanner = new Scan(); scanner.setMaxResultSize(numRows); ResultScanner resultScanner = table.getScanner(scanner); cellValues = Arrays.stream(resultScanner.next(numRows)). map(Result::listCells).flatMap(List::stream). map(CellUtil::cloneValue).map(Bytes::toString). collect(Collectors.toList()); }catch(IOException e){ throw new RuntimeException("unable to retrieve the data from HBase table ", e); } return cellValues; } public void deleteTable(String tableName) { try { if (admin.tableExists(TableName.valueOf(tableName))) { //we need to disable the table before deletion admin.disableTable(TableName.valueOf(tableName)); admin.deleteTable(TableName.valueOf(tableName)); } }catch(IOException e){ throw new RuntimeException("unable to delete HBase table ", e); } } public void closeCon() { try { admin.close(); connection.close(); }catch(IOException e){ throw new RuntimeException(e); } } } |