[7] | 1 | /** |
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| 2 | * Program: HBaseClient.java |
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| 3 | * Editor: Waue Chen |
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| 4 | * From : NCHC. Taiwn |
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| 5 | * Last Update Date: 06/10/2008 |
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| 6 | */ |
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| 7 | |
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[8] | 8 | package tw.org.nchc.code; |
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[7] | 9 | |
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| 10 | import java.io.IOException; |
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| 11 | import java.util.SortedMap; |
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| 12 | import java.util.TreeMap; |
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| 13 | |
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| 14 | import org.apache.hadoop.hbase.HBaseConfiguration; |
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| 15 | import org.apache.hadoop.hbase.HScannerInterface; |
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| 16 | import org.apache.hadoop.hbase.HStoreKey; |
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| 17 | import org.apache.hadoop.hbase.HTable; |
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| 18 | import org.apache.hadoop.io.Text; |
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| 19 | |
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| 20 | /** |
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| 21 | * Demo that illustrates the HBase client API. |
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| 22 | * The demo program will insert values to " Column Family: Column qualifier" and then print these. |
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| 23 | * pre-do : create a hbase table "test_table" with (CF:CI) which (" column family ", " column qualifier ") |
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| 24 | * 1. $ bin/hbase shell |
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| 25 | * 2. > create table test_table("CF"); |
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| 26 | * ok ! we can test it |
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| 27 | * 3. > insert into test_table("CF:CI") values=("Hellow World") where row = "1"; |
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| 28 | * 4. > select * from test_table; |
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| 29 | |
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| 30 | 08/06/03 16:16:36 INFO hbase.HTable: Creating scanner over test_table starting at key |
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| 31 | +---------+-----------+-----------+ |
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| 32 | | Row | Column | Cell | |
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| 33 | +---------+-----------+-----------+ |
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| 34 | | 1 | CF:CI | Hellow World | |
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| 35 | +---------+-----------+-----------+ |
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| 36 | 1 row(s) in set. (0.24 sec) |
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| 37 | |
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| 38 | * on the structure , "Row" means Row ID which is a key to describe a column; |
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| 39 | * Column means the database structure in test_table, |
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| 40 | * Column Family , "CF", should be defined while creating table. |
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| 41 | * Column qualifier , "CI" , can be added dynamically. |
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| 42 | * Cell is the value of CF:CI |
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| 43 | * |
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| 44 | * that's the structure; then the demo program will show you in console as below : |
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| 45 | * |
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| 46 | Illustration of adding data... |
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| 47 | Writing row = 0, col 'CF:CI' = Hellow0 |
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| 48 | Writing row = 1, col 'CF:CI' = Hellow1 |
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| 49 | Writing row = 2, col 'CF:CI' = Hellow2 |
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| 50 | Writing row = 3, col 'CF:CI' = Hellow3 |
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| 51 | Writing row = 4, col 'CF:CI' = Hellow4 |
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| 52 | Writing row = 5, col 'CF:CI' = Hellow5 |
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| 53 | Writing row = 6, col 'CF:CI' = Hellow6 |
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| 54 | Writing row = 7, col 'CF:CI' = Hellow7 |
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| 55 | Writing row = 8, col 'CF:CI' = Hellow8 |
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| 56 | Writing row = 9, col 'CF:CI' = Hellow9 |
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| 57 | |
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| 58 | Illustration of querying... |
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| 59 | row = 1, 'CF : CI ' = Hellow1 |
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| 60 | |
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| 61 | Illustration of scanning... |
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| 62 | 08/06/03 16:47:51 INFO hbase.HTable: Creating scanner over test_table starting at key |
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| 63 | row = 0//9223372036854775807, col 'CF:CI' = Hellow0 |
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| 64 | row = 1//9223372036854775807, col 'CF:CI' = Hellow1 |
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| 65 | row = 2//9223372036854775807, col 'CF:CI' = Hellow2 |
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| 66 | row = 3//9223372036854775807, col 'CF:CI' = Hellow3 |
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| 67 | row = 4//9223372036854775807, col 'CF:CI' = Hellow4 |
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| 68 | row = 5//9223372036854775807, col 'CF:CI' = Hellow5 |
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| 69 | row = 6//9223372036854775807, col 'CF:CI' = Hellow6 |
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| 70 | row = 7//9223372036854775807, col 'CF:CI' = Hellow7 |
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| 71 | row = 8//9223372036854775807, col 'CF:CI' = Hellow8 |
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| 72 | row = 9//9223372036854775807, col 'CF:CI' = Hellow9 |
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| 73 | |
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| 74 | |
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| 75 | * |
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| 76 | */ |
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| 77 | public class HBaseClient { |
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| 78 | |
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| 79 | public static void main(String[] args) throws IOException { |
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| 80 | |
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| 81 | // Open the "test_table" table. If it hasn't been in Hbase, you should create. |
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| 82 | HBaseConfiguration conf = new HBaseConfiguration(); |
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| 83 | HTable table = new HTable(conf, new Text("test_table")); |
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| 84 | |
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| 85 | System.out.println("Illustration of adding data..."); |
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| 86 | |
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| 87 | // create column formed (Column Family:Column qualifier) |
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| 88 | Text column = new Text("CF:CI"); |
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| 89 | |
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| 90 | // create row_id |
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| 91 | Text row_id = new Text(); |
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| 92 | |
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| 93 | // demo 1 : Insert ten demo values |
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| 94 | for (int i = 0; i < 10; i++) { |
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| 95 | |
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| 96 | // give row_id value |
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| 97 | row_id.set(new Integer(i).toString()); |
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| 98 | |
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| 99 | // let "indicate_id" indicate the column which row = row_id |
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| 100 | long indicate_id= table.startUpdate(row_id); |
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| 101 | |
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| 102 | //val = value of CF:CI where row_id = i |
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| 103 | Text val = new Text("Hellow" + i); |
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| 104 | |
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| 105 | // put "val" to "column" from "table" where "row_id" |
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| 106 | // the same as : |
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| 107 | // hql> INSERT INTO table( column ) VALUES=( val) WHERE ROW = row_id ; |
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| 108 | table.put(indicate_id, column, val.getBytes()); |
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| 109 | table.commit(indicate_id); |
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| 110 | |
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| 111 | System.out.println("Writing row = " + row_id + ", col '" + column |
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| 112 | + "' = " + val); |
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| 113 | } |
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| 114 | |
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| 115 | // demo 2 : print column value only row = 1 ; |
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| 116 | System.out.println("\n Querying row = 1"); |
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| 117 | |
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| 118 | // Get a single value for the specified row and column |
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| 119 | // byte[] = HTable.get(Text row, Text column) |
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| 120 | |
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| 121 | String s = Text.decode(table.get(new Text("1"),new Text("CF:CI"))); |
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| 122 | // if change as |
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| 123 | // String s = (table.get(new Text("1"),new Text("CF:CI"))).toString(); |
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| 124 | // will get chaos code " [B@1f14ceb" |
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| 125 | System.out.println("row = 1, 'CF : CI ' = " + s); |
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| 126 | |
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| 127 | // demo 3 : Print the all contents of this table |
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| 128 | System.out.println("\nIllustration of scanning..."); |
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| 129 | |
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| 130 | // we only want one column, but you can specify multiple columns to |
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| 131 | // fetch at once |
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| 132 | Text[] cols = { column }; |
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| 133 | |
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| 134 | // Use HScannerInterface to crawl table |
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| 135 | HScannerInterface scanner = table.obtainScanner(cols, new Text()); |
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| 136 | |
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| 137 | // column values are stored in a Map |
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| 138 | SortedMap<Text, byte[]> values = new TreeMap<Text, byte[]>(); |
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| 139 | HStoreKey currentKey = new HStoreKey(); |
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| 140 | while (scanner.next(currentKey, values)) { |
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| 141 | // decode the stored byte[] back into a String |
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| 142 | String val = Text.decode(values.get(column)); |
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| 143 | System.out.println("row = " + currentKey + ", col '" + column + "' = " |
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| 144 | + val); |
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| 145 | } |
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| 146 | |
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| 147 | // remember to close scanner when done |
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| 148 | scanner.close(); |
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| 149 | |
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| 150 | } |
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| 151 | |
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| 152 | } |
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