HBASE编程实践

编程实现以下功能
createTable(String tableName, String[] fields)
创建表，参数tableName为表的名称，字符串数组fields为存储记录各个字段名称的数组。要求当HBase已经存在名为tableName的表的时候，先删除原有的表，然后再创建新的表。

addRecord(String tableName, String row, String[] fields, String[] values)
向表tableName、行row（用S_Name表示）和字符串数组fields指定的单元格中添加对应的数据values。其中，fields中每个元素如果对应的列族下还有相应的列限定符的话，用“columnFamily:column”表示。例如，同时向“Math”、“Computer
Science”、“English”三列添加成绩时，字符串数组fields为{“Score:Math”, ”Score:Computer Science”,
”Score:English”}，数组values存储这三门课的成绩。

scanColumn(StringtableName, String column）
浏览表tableName某一列的数据，如果某一行记录中该列数据不存在，则返回null。要求当参数column为某一列族名称时，如果底下有若干个列限定符，则要列出每个列限定符代表的列的数据；当参数column为某一列具体名称（例如“Score:Math”）时，只需要列出该列的数据。

modifyData(String tableName, String row, String column)
修改表tableName，行row（可以用学生姓名S_Name表示），列column指定的单元格的数据。

deleteRow(String tableName,String row)
删除表tableName中row指定的行的记录。

public class hbaseexp {
    public static Configuration configuration;
    public static Connection connection;
    public static Admin admin； 
    public static void listName() throws IOException{
     init();
     HTableDescriptor[] tables = admin.listTables(); 
     for(HTableDescriptor s:tables){
      System.out.println(s.getNameAsString());
     }
     close();
    }
    public static void scanAll(String tableName) throws IOException{
     init();
     TableName table = TableName.valueOf(tableName);
     if(!admin.tableExists(table)){
      System.out.println("table is not exists");
     }else{
      Table t = connection.getTable(table);
      Scan scan = new Scan();
      ResultScanner rs = t.getScanner(scan);
      for(Result s :rs){
       for(Cell cell:s.rawCells()){
        System.out.print("row name:"+new String(CellUtil.cloneRow(cell)));
        System.out.print("column family :" +new String(CellUtil.cloneFamily(cell)));
        System.out.print("column :"+new String(CellUtil.cloneQualifier(cell)));
        System.out.print("value :"+new String(CellUtil.cloneValue(cell)));
        System.out.print("timestamp :"+cell.getTimestamp());
        System.out.println();
       }
             }
     }
     close();
    }
    public static void dropTable(String tableName) throws IOException{
     init();
     TableName tablename = TableName.valueOf(tableName);
  if(!admin.tableExists(tablename)){
   System.out.println("tale is not exists");
  }else{
   //disable drop
   admin.disableTable(tablename);
   admin.truncateTable(tablename, false);
   System.out.println("all data is delete");
  }
  close();
    }
    public static void countRows(String tableName) throws IOException{
     //key-value number? row number?
     init();
     Table table = connection.getTable(TableName.valueOf(tableName));
  Scan scan = new Scan();
  ResultScanner scanner = table.getScanner(scan);
  int num = 0;
  for(Result s = scanner.next(); s!=null;s = scanner.next())
   num++;
  System.out.println("numbers of  elements is : " + num);
     close();
    }
    public static void createTable(String tableName, String[] fields) throws IOException {
        init();
        TableName tablename = TableName.valueOf(tableName);
        if (admin.tableExists(tablename)) {
            System.out.println("table is exists!");
            admin.disableTable(tablename);
            admin.deleteTable(tablename);
        }
        HTableDescriptor hTableDescriptor = new HTableDescriptor(tablename);
        for (String str : fields) {
            HColumnDescriptor hColumnDescriptor = new HColumnDescriptor(str);
            hTableDescriptor.addFamily(hColumnDescriptor);
        }
        admin.createTable(hTableDescriptor);
        close();
    }
    public static void addRecord(String tableName, String row, String[] fields, String[] values) throws IOException {
     
        init();
        Table table = connection.getTable(TableName.valueOf(tableName));
        for (int i = 0; i != fields.length; i++) {
            Put put = new Put(row.getBytes());
            String[] cols = fields[i].split(":");
            put.addColumn(cols[0].getBytes(), cols[1].getBytes(), values[i].getBytes());
            table.put(put);
        }
        table.close();
        close();
    }
    public static void showCell(Result result) {
        Cell[] cells = result.rawCells();
        for (Cell cell : cells) {
            System.out.println("RowName is :" + new String(CellUtil.cloneRow(cell)) + " ");
            System.out.println("column Family is :" + new String(CellUtil.cloneFamily(cell)) + " ");
            System.out.println("row Name is :" + new String(CellUtil.cloneQualifier(cell)) + " ");
            System.out.println("value is :" + new String(CellUtil.cloneValue(cell)) + " ");
            System.out.println("Timetamp is :" + cell.getTimestamp() + " ");
        }
    }
    public static void scanColumn(String tableName, String column) throws IOException {
        init();
        Table table = connection.getTable(TableName.valueOf(tableName));
        Scan scan = new Scan();
        if(column.indexOf(":")==-1)
         scan.addFamily(Bytes.toBytes(column));//column already is a family or its own name
        else{
         String tFamily=column.substring(0, column.indexOf(":"));
         String tQualifier=column.substring(column.indexOf(":")+1, column.length());
         scan.addColumn(Bytes.toBytes(tFamily), Bytes.toBytes(tQualifier));
        }
        ResultScanner scanner = table.getScanner(scan);
        for (Result result = scanner.next(); result != null; result = scanner.next()) {
            showCell(result);
        }
        table.close();
        close();
    }
    public static void modifyData(String tableName, String row, String column, String val) throws IOException {
        init();
        Table table = connection.getTable(TableName.valueOf(tableName));
        Put put = new Put(row.getBytes());
        long ts=System.currentTimeMillis();   
        put.addColumn(row.getBytes(), column.getBytes(), ts, val.getBytes());
        table.put(put);
        table.close();
        close();
    }
    public static void deleteRow(String tableName, String row) throws IOException {
        init();
        Table table = connection.getTable(TableName.valueOf(tableName));
        Delete delete=new Delete(row.getBytes());
        //delete.addColumn(family, qualifier) delete specific column
        table.delete(delete);
        table.close();
        close();
    }
//start a connection
    public static void init() {
        configuration = HBaseConfiguration.create();
        configuration.set("hbase.rootdir", "hdfs://localhost:9000/hbase");
        try {
            connection = ConnectionFactory.createConnection(configuration);
            admin = connection.getAdmin();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    //end a connection
    public static void close() {
        try {
            if (admin != null) {
                admin.close();
            }
            if (null != connection) {
                connection.close();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    
    public static void main(String[] args) {
     //API use https://www.cnblogs.com/frankdeng/p/9310209.html thanks
     String[]ColFamily={"Score","Level"};
        String[] fields = {"Score:Math", "Score:Computer", "Score:English","Level:All"};
        String[] values = {"90", "80", "60","A"};
        try {
            createTable("HDFSEXP", ColFamily);
            addRecord("HDFSEXP", "row1", fields, values);
            scanColumn("HDFSEXP","Level:All");
            modifyData("HDFSEXP", "Score", "Math", "100");
            deleteRow("HDFSEXP", "row1");
            System.out.println("finish");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    }