小白入门篇| HBase1.0+ java-api介绍

Posted 2021-04-19 ITPUB技术小栈

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作者：cjfeii

鸣谢：感谢ChinaUnix技术社区的cjfeii提供稿件，如需转载，请注明出处。

在网上查了hbase的java client api的介绍，发现很多都是之前的版本，虽然现在还可以运行，但是里面有很多不建议使用（@deprecated）的class及相关方法。其中很关键的就是增加了Connection类，使其给人感觉更像一个专业的客户端api，还有就是用Admin替换了HBaseAdmin，还有一些细节上的修改，比如：增加了TableName，获取数据的时候用Cell替换KeyValue，以及其他的一些修改。

本文主要介绍了这样的一些改动，并写了一些常用操作的代码以供参考。

1. 创建config和connection

org.apache.hadoop.hbase.client.Connection是 hbase从 0.99.0开始增加的类，Connection主要创建一个 hbase客户端连接，用于和 hbase通信：

Configuration conf = HBaseConfiguration.create();

conf.addResource("hbase-site.xml");

Connection connect = ConnectionFactory.createConnection(conf);

2. 创建表

0.99.0之前的版本主要用HBaseAdmin创建新的 Table，但是在 0 .99.0之后，可以直接用Admin来 create, drop, list, enable, disable Table了。

还有一个要注意的，在操作 table的过程中，表名称不能再用String类型，而需要用TableName类型了：

/* test create table. */

publicstaticvoid createTable(String tableName, String[] family)

            throws Exception {

        Admin admin = connect.getAdmin();

TableNametn = TableName.valueOf(tableName);

HTableDescriptordesc = newHTableDescriptor(tn);

for (inti = 0; i<family.length; i++) {

desc.addFamily(newHColumnDescriptor(family[i]));

        }

if (admin.tableExists(tn)) {

System.out.println("table Exists!");

System.exit(0);

        } else {

admin.createTable(desc);

System.out.println("create table Success!");

        }

    }

3. 写入数据

新的版本中（ 0.99.0+）还有一个重要的改动是，HTable不再是客户端 api，一些操作 Table的动作（ get, put, delete, scan）都需要直接用Table class来完成：

/* put data into table. */

    public static void addData(String rowKey, String tableName,

            String[] column1, String[] value1, String[] column2, String[] value2)

            throws IOException {

/* get table. */

TableNametn = TableName.valueOf(tableName);

        Table table = connect.getTable(tn);

/* create put. */

        Put put = new Put(Bytes.toBytes(rowKey));

HColumnDescriptor[] columnFamilies = table.getTableDescriptor().getColumnFamilies();

        for (inti = 0; i<columnFamilies.length; i++) {

            String f = columnFamilies[i].getNameAsString();

            if (f.equals("article")) {

                for (int j = 0; j < column1.length; j++) {

put.addColumn(Bytes.toBytes(f), Bytes.toBytes(column1[j]), Bytes.toBytes(value1[j]));

                }

            }

            if (f.equals("author")) {

                for (int j = 0; j < column2.length; j++) {

put.addColumn(Bytes.toBytes(f), Bytes.toBytes(column2[j]), Bytes.toBytes(value2[j]));

                }

            }

        }

/* put data. */

table.put(put);

System.out.println("add data Success!");

    }

4. 获取数据

获取数据的时候，在0.96.0及之后的版本，有一个很重要的改动就是，弃用了Result class中的public List<KeyValue> list()方法，统统改用public List<Cell>listCells()方法：

/* get data. */

    public static void getResult(String tableName, String rowKey)

            throws IOException {

/* get table. */

        Table table = connect.getTable(TableName.valueOf(tableName));

        Get get = new Get(Bytes.toBytes(rowKey));

        Result result = table.get(get);

        for (Cell cell : result.listCells()) {

System.out.println("------------------------------------");

System.out.println("rowkey: " + new String(CellUtil.cloneRow(cell)));

System.out.println("family: " + new String(CellUtil.cloneFamily(cell)));

System.out.println("column: " + new String(CellUtil.cloneQualifier(cell)));

System.out.println("value : " + new String(CellUtil.cloneValue(cell)));

System.out.println("timest: " + cell.getTimestamp());

        }

    }

5. 遍历表数据

/* scan table. */

    public static void getResultScan(String tableName) throws IOException {

        Scan scan = new Scan();

ResultScannerrs = null;

        Table table = connect.getTable(TableName.valueOf(tableName));

        try {

rs = table.getScanner(scan);

            for (Result r : rs) {

                for (Cell cell : r.listCells()) {

System.out.println("------------------------------------");

System.out.println("rowkey: " + new String(CellUtil.cloneRow(cell)));

System.out.println("family: " + new String(CellUtil.cloneFamily(cell)));

System.out.println("column: " + new String(CellUtil.cloneQualifier(cell)));

System.out.println("value : " + new String(CellUtil.cloneValue(cell)));

System.out.println("timest: " + cell.getTimestamp());

                }

            }

        } finally {

rs.close();

        }

    }

6. 遍历一定范围的表数据

/* range scan table. */

    public static void getResultScan(String tableName, String start_rowkey,

            String stop_rowkey) throws IOException {

        Scan scan = new Scan();

scan.setStartRow(Bytes.toBytes(start_rowkey));

scan.setStopRow(Bytes.toBytes(stop_rowkey));

ResultScannerrs = null;

        Table table = connect.getTable(TableName.valueOf(tableName));

        try {

rs = table.getScanner(scan);

            for (Result r : rs) {

                for (Cell cell : r.listCells()) {

System.out.println("------------------------------------");

System.out.println("rowkey: " + new

String(CellUtil.cloneRow(cell)));

System.out.println("family: " + new

String(CellUtil.cloneFamily(cell)));

System.out.println("column: " + new String(CellUtil.cloneQualifier(cell)));

System.out.println("value : " + new String(CellUtil.cloneValue(cell)));

System.out.println("timest: " + cell.getTimestamp());

                }

            }

        } finally {

rs.close();

        }

    }

7. 获取指定行指定列数据

/* get column data. */

    public static void getResultByColumn(String tableName, String rowKey,

            String familyName, String columnName) throws IOException {

/* get table. */

        Table table = connect.getTable(TableName.valueOf(tableName));

        Get get = new Get(Bytes.toBytes(rowKey));

get.addColumn(Bytes.toBytes(familyName), Bytes.toBytes(columnName)); // 获取指定列族和列修饰符对应的列

        Result result = table.get(get);

        for (Cell cell : result.listCells()) {

System.out.println("------------------------------------");

System.out.println("rowkey: " + new

String(CellUtil.cloneRow(cell)));

System.out.println("family: " + new

String(CellUtil.cloneFamily(cell)));

System.out.println("column: " + new String(CellUtil.cloneQualifier(cell)));

System.out.println("value : " + new String(CellUtil.cloneValue(cell)));

System.out.println("timest: " + cell.getTimestamp());

}

}

8. 修改列数据

和之前的实现类似，就是直接覆盖：

/* update. */

public static voidupdateTable(StringtableName,

String rowKey,

String familyName, StringcolumnName, String value)

            throws IOException {

        Table table = connect.getTable(TableName.valueOf(tableName));

        Put put = new Put(Bytes.toBytes(rowKey));

put.addColumn(Bytes.toBytes(familyName), Bytes.toBytes(columnName),

Bytes .toBytes(value));

table.put(put);

System.out.println("update table Success!");

    }

9. 获得多个版本的数据

/* get multi-version data. */

    public static void getResultByVersion(String tableName, String rowKey,

            String familyName, String columnName) throws IOException {

        Table table = connect.getTable(TableName.valueOf(tableName));

        Get get = new Get(Bytes.toBytes(rowKey));

get.addColumn(Bytes.toBytes(familyName), Bytes.toBytes(columnName));

get.setMaxVersions(5);

        Result result = table.get(get);

        for (Cell cell : result.listCells()) {

System.out.println("------------------------------------");

System.out.println("timest: " + cell.getSequenceId());

System.out.println("rowkey: " + new String(CellUtil.cloneRow(cell)));

System.out.println("family: " + new String(CellUtil.cloneFamily(cell)));

System.out.println("column: " + new String(CellUtil.cloneQualifier(cell)));

System.out.println("value : " + new String(CellUtil.cloneValue(cell)));

System.out.println("timest: " + cell.getTimestamp());

        }

    }

10. 删除数据

以下方法包括删除列、行数据：

/* delete column. */

public static voiddeleteColumn(StringtableName,

String rowKey,

String falilyName, StringcolumnName) throws IOException {

        Table table = connect.getTable(TableName.valueOf(tableName));

        Delete deleteColumn = new

Delete(Bytes.toBytes(rowKey));

deleteColumn.addColumns(Bytes.toBytes(falilyName), Bytes.toBytes(columnName));

table.delete(deleteColumn);

System.out.println(falilyName + ":" + columnName + "is deleted!");

    }

/* delete row. */

public static voiddeleteAllColumn(StringtableName, StringrowKey)

            throws IOException {

        Table table = connect.getTable(TableName.valueOf(tableName));

        Delete deleteAll = new Delete(Bytes.toBytes(rowKey));

table.delete(deleteAll);

System.out.println("all columns are deleted!");

}

11. 删除表

和创建表一样，都需要Admin来删除表：

/* delete table. */

    public static void deleteTable(String tableName) throws IOException {

        Admin admin = connect.getAdmin();

admin.disableTable(TableName.valueOf(tableName));

admin.deleteTable(TableName.valueOf(tableName));

System.out.println(tableName + "is deleted!");

    }