Hbase Java API:
secureCRTXstart远程桌面连接
maven项目pom文件maven-cdh仓库地址hbase&Hadoop依赖
createTable ->读取配置文件HbaseConfiguration Hbaseconfiguration.create();
create HbaseAdmin -> HbaseAdmin admin =
new HbaseAdmin(conf); // hbase中对于表的操作封装成为了一个类为HbaseAdmin
表是否存在admin.tableExists(Bytes.toBytes(“t1”));
admin.disableTable(Bytes.toBytes(“t1”)); //先禁用再删除
admin.deleteTable(Bytes.toBytes(“t1”));
HTableDescriptor desc = new HTableDescriptor(TableName.valueOf(“t1”));
desc.addFamily(newHColumnDescriptor(Bytes.toBytes(“info”)));
admin.createTable(HTableDescriptor desc); //新建表的描述对象
//关闭资源
Admin.colse();
getTable() ->
创建配置文件
Configuration conf =HbaseConfiguration.create();
创建一个表
HTable table = newHtable(conf,Bytes.toBytes(“t1”));
//数据插入Put
Put put = new Put(RowKey :Bytes.toBytes(“rk00001”));
Put.add(Bytes.toBytes(“info”), Bytes.toBytes(“name”),Bytes.toBytes(“lisi”));
Table.put(put);
// close resource
Table.close();
getData ->
Get get = newGet(Bytes.toBytes(“rk00001”));
Result rs = table.get(get);
Result.getValue(Bytes.toBytes(“info”), Bytes.toBytes(“name”));// Bytes Array
For(Cell cel:result.rawCells()) {
Cell.getFamily() // deprecatedctrl+o弹出所有方法
CellUtil. cloneFamily(cell);
CellUtil. cloneQualifier(cell); // Bytes
CellUtil. cloneRow(cell);
CellUtil. cloneValue(cell);
}
命名空间//
HbaseAdmin对象instance
NamespaceDescriptor descriptor =NamespaceDescriptor.create(“ns1”).build();
Admin.createNamespace(descriptor);
Admin.close();
Hbase全表扫描注意异常处理
Htable -> close resourceIOUtils.closeStream(table);
getTable -> scan(create Scaneinterface)getScanner(ResultScanner)-> Result
printResult -> Cell rs.rawCells()Bytes.toString(CellUtil.cloneFamily(cell))
family row qualifier value()列族rowkey列名值
范围查询：
StartRow(startRowKey:Bytes.toBytes(“”))stopRow(stopRowKey:Bytes.toBytes(“”)包头不包
尾scan.addfamily(Bytes.toBytes(“columnFamily”))
缓存set cache
Scan.setCacheBlocks(false)默认值为true
本地缓存数据一般只使用一次
Batch列缓存setBatch(2)每次返回的列有两行
setcaching行缓存setCaching(2)10行数据读取5次默认不缓存
setACL(permission) // set permission
过滤器：
ColumnPrefixFilter前缀过滤器
ColumnFilter列族过滤器
PageFilter分页过滤器
ByteArrayComparable过滤器与比较器结合使用
// filter
Table = getTable();
Scan scan = new Scan();
Filter filter = newColumnPrefixFilter(Bytes.toBytes(“rk”));//查看实现接口的类ctrl+7eclipseprefixFilter过滤rowkey
Filter = new PageFilter(3); //三条记录分页指定查询的条数
Scan.setFilter(filter);
Table.getScanner(scan);
// create hbase comparator
ByteArrayComparable com = null;
com = new subStringComparator(“lisi”);
filter = new SingleColumnValueFilter(
family,// BytestoBytes(“info”)
qualifier, // BytestoBytes(“name”)
compareOp,// compareOp.EQUAL
value // com
)
