| 1 | = Sample Code of Show Hbase Write&Read by Map-Reduce " = |
| 2 | == Abstract == |
| 3 | The demo program will insert values to " Column Family: Column Identify" and then print these. |
| 4 | |
| 5 | * pre-do : create a hbase table "test_table" with (CF:CI) which (" column family ", " column ID ") [[BR]] |
| 6 | |
| 7 | 1 $ bin/hbase shell [[BR]] |
| 8 | 2 > create table test_table("CF"); [[BR]] |
| 9 | ok ! we can test it [[BR]] |
| 10 | 3 > insert into test_table("CF:CI") values=("Hellow World") where row = "1"; [[BR]] |
| 11 | 4 > select * from test_table; [[BR]] |
| 12 | {{{ |
| 13 | 08/06/03 16:16:36 INFO hbase.HTable: Creating scanner over test_table starting at key |
| 14 | +---------+-----------+-----------+ |
| 15 | | Row | Column | Cell | |
| 16 | +---------+-----------+-----------+ |
| 17 | | 1 | CF:CI | Hellow World | |
| 18 | +---------+-----------+-----------+ |
| 19 | 1 row(s) in set. (0.24 sec) |
| 20 | }}} |
| 21 | |
| 22 | on the structure , '''Row''' means Row ID which is a key to describe a column; [[br]] |
| 23 | '''Column''' means the database structure in test_table, [[br]] |
| 24 | Column Family , "CF", should be defined while creating table. [[br]] |
| 25 | Column Id , "CI" , can be added dynamically. [[br]] |
| 26 | '''Cell''' is the value of CF:CI [[br]] |
| 27 | |
| 28 | == Output == |
| 29 | |
| 30 | That's the structure; then the demo program will show you in console as below : |
| 31 | |
| 32 | {{{ |
| 33 | Illustration of adding data... |
| 34 | Writing row = 0, col 'CF:CI' = Hellow0 |
| 35 | Writing row = 1, col 'CF:CI' = Hellow1 |
| 36 | Writing row = 2, col 'CF:CI' = Hellow2 |
| 37 | Writing row = 3, col 'CF:CI' = Hellow3 |
| 38 | Writing row = 4, col 'CF:CI' = Hellow4 |
| 39 | Writing row = 5, col 'CF:CI' = Hellow5 |
| 40 | Writing row = 6, col 'CF:CI' = Hellow6 |
| 41 | Writing row = 7, col 'CF:CI' = Hellow7 |
| 42 | Writing row = 8, col 'CF:CI' = Hellow8 |
| 43 | Writing row = 9, col 'CF:CI' = Hellow9 |
| 44 | |
| 45 | Illustration of querying... |
| 46 | row = 1, 'CF : CI ' = Hellow1 |
| 47 | |
| 48 | Illustration of scanning... |
| 49 | 08/06/03 16:47:51 INFO hbase.HTable: Creating scanner over test_table starting at key |
| 50 | row = 0//9223372036854775807, col 'CF:CI' = Hellow0 |
| 51 | row = 1//9223372036854775807, col 'CF:CI' = Hellow1 |
| 52 | row = 2//9223372036854775807, col 'CF:CI' = Hellow2 |
| 53 | row = 3//9223372036854775807, col 'CF:CI' = Hellow3 |
| 54 | row = 4//9223372036854775807, col 'CF:CI' = Hellow4 |
| 55 | row = 5//9223372036854775807, col 'CF:CI' = Hellow5 |
| 56 | row = 6//9223372036854775807, col 'CF:CI' = Hellow6 |
| 57 | row = 7//9223372036854775807, col 'CF:CI' = Hellow7 |
| 58 | row = 8//9223372036854775807, col 'CF:CI' = Hellow8 |
| 59 | row = 9//9223372036854775807, col 'CF:CI' = Hellow9 |
| 60 | }}} |
| 61 | |
| 62 | == code == |
| 63 | |
| 64 | {{{ |
| 65 | /* |
| 66 | * DemoHBaseClient.java |
| 67 | */ |
| 68 | |
| 69 | // package tw.org.nchc.demo; |
| 70 | |
| 71 | import java.io.IOException; |
| 72 | import java.util.SortedMap; |
| 73 | import java.util.TreeMap; |
| 74 | |
| 75 | import org.apache.hadoop.hbase.HBaseConfiguration; |
| 76 | import org.apache.hadoop.hbase.HScannerInterface; |
| 77 | import org.apache.hadoop.hbase.HStoreKey; |
| 78 | import org.apache.hadoop.hbase.HTable; |
| 79 | import org.apache.hadoop.io.Text; |
| 80 | |
| 81 | |
| 82 | public class DemoHBaseClient { |
| 83 | |
| 84 | public static void main(String[] args) throws IOException { |
| 85 | |
| 86 | // Open the "test_table" table. If it hasn't been in Hbase, you should create. |
| 87 | HBaseConfiguration conf = new HBaseConfiguration(); |
| 88 | HTable table = new HTable(conf, new Text("test_table")); |
| 89 | |
| 90 | System.out.println("Illustration of adding data..."); |
| 91 | |
| 92 | // create column formed (Column Family:Column Id) |
| 93 | Text column = new Text("CF:CI"); |
| 94 | |
| 95 | // create row_id |
| 96 | Text row_id = new Text(); |
| 97 | |
| 98 | // demo 1 : Insert ten demo values |
| 99 | for (int i = 0; i < 10; i++) { |
| 100 | |
| 101 | // give row_id value |
| 102 | row_id.set(new Integer(i).toString()); |
| 103 | |
| 104 | // let "indicate_id" indicate the column which row = row_id |
| 105 | long indicate_id= table.startUpdate(row_id); |
| 106 | |
| 107 | //val = value of CF:CI where row_id = i |
| 108 | Text val = new Text("Hellow" + i); |
| 109 | |
| 110 | // put "val" to "column" from "table" where "row_id" |
| 111 | // the same as : |
| 112 | // hql> INSERT INTO table( column ) VALUES=( val) WHERE ROW = row_id ; |
| 113 | table.put(indicate_id, column, val.getBytes()); |
| 114 | table.commit(indicate_id); |
| 115 | |
| 116 | System.out.println("Writing row = " + row_id + ", col '" + column |
| 117 | + "' = " + val); |
| 118 | } |
| 119 | |
| 120 | // demo 2 : print column value only row = 1 ; |
| 121 | System.out.println("\n Querying row = 1"); |
| 122 | |
| 123 | // Get a single value for the specified row and column |
| 124 | // byte[] = HTable.get(Text row, Text column) |
| 125 | |
| 126 | String s = Text.decode(table.get(new Text("1"),new Text("CF:CI"))); |
| 127 | // if change as |
| 128 | // String s = (table.get(new Text("1"),new Text("CF:CI"))).toString(); |
| 129 | // will get chaos code " [B@1f14ceb" |
| 130 | System.out.println("row = 1, 'CF : CI ' = " + s); |
| 131 | |
| 132 | // demo 3 : Print the all contents of this table |
| 133 | System.out.println("\nIllustration of scanning..."); |
| 134 | |
| 135 | // we only want one column, but you can specify multiple columns to |
| 136 | // fetch at once |
| 137 | Text[] cols = { column }; |
| 138 | |
| 139 | // Use HScannerInterface to crawl table |
| 140 | HScannerInterface scanner = table.obtainScanner(cols, new Text()); |
| 141 | |
| 142 | // column values are stored in a Map |
| 143 | SortedMap<Text, byte[]> values = new TreeMap<Text, byte[]>(); |
| 144 | HStoreKey currentKey = new HStoreKey(); |
| 145 | while (scanner.next(currentKey, values)) { |
| 146 | // decode the stored byte[] back into a String |
| 147 | String val = Text.decode(values.get(column)); |
| 148 | System.out.println("row = " + currentKey + ", col '" + column + "' = " |
| 149 | + val); |
| 150 | } |
| 151 | |
| 152 | // remember to close scanner when done |
| 153 | scanner.close(); |
| 154 | |
| 155 | } |
| 156 | |
| 157 | } |
| 158 | |
| 159 | }}} |