MAPREDUCE服务 MRS-使用Scan读取HBase数据:代码样例

时间：2024-11-25 19:32:58

MAPREDUCE服务 MRS

代码样例

以下代码片段在com.huawei.bigdata.hbase.examples包的“HBaseExample”类的testScanData方法中

public void testScanData() {
     LOG .info("Entering testScanData.");

    Table table = null;
    // Instantiate a ResultScanner object.
    ResultScanner rScanner = null;
    try {
        // Create the Configuration instance.
        table = conn.getTable(tableName);

        // Instantiate a Get object.
        Scan scan = new Scan();
        scan.addColumn(Bytes.toBytes("info"), Bytes.toBytes("name"));


        // Set the Caching size.
        scan.setCaching(1000);//注[1]

        // Submit a scan request.
        rScanner = table.getScanner(scan);

        // Print query results.
        for (Result r = rScanner.next(); r != null; r = rScanner.next()) {
            for (Cell cell : r.rawCells()) {
               LOG.info(Bytes.toString(CellUtil.cloneRow(cell)) + ":"
                + Bytes.toString(CellUtil.cloneFamily(cell)) + ","
                + Bytes.toString(CellUtil.cloneQualifier(cell)) + ","
                + Bytes.toString(CellUtil.cloneValue(cell)));
            }
        }
        LOG.info("Scan data successfully.");
    } catch (IOException e) {
        LOG.error("Scan data failed ", e);
    } finally {
        if (rScanner != null) {
            // Close the scanner object.
            rScanner.close();
        }
        if (table != null) {
            try {
                // Close the HTable object.
                table.close();
            } catch (IOException e) {
                LOG.error("Close table failed ", e);
            }
        }
    }
    LOG.info("Exiting testScanData.");
}

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