Hbase Java API

Correspondence between several related classes and hbase Data Models

Java class	Hbase Data Model
Hbaseadmin	Database)
Hbaseconfiguration
Htable	Table)
Htabledescriptor	Column family)
Put	Column modifier (column qualifier)
Get
Bytes

 

I. hbaseconfiguration

Link: org. Apache. hadoop. hbase. hbaseconfiguration

Purpose: Configure hbase

Return Value	Function	Description
Void	Addresource (path file)	Add resources by specifying the file in the specified path
Void	Clear ()	Clear all set properties
String	Get (string name)	Get the value corresponding to the property name
String	Getboolean (string name, Boolean defaultvalue)	Obtain the attribute value of the boolean type. If the attribute value type is Boolean, the default attribute value is returned.
Void	Set (string name, string value)	Set Value Through attribute name
Void	Setboolean (string name, Boolean value)	Set attribute values of the Boolean Type

Usage example:

HBaseConfiguration hconfig = new HBaseConfiguration();hconfig.set("hbase.zookeeper.property.clientPort","2181");

This method sets "hbase. zookeeper. Property. clientport" to 2181. Generally, hbaseconfiguration uses constructors for initialization and other methods.

Ii. hbaseadmin

Link: org. Apache. hadoop. hbase. Client. hbaseadmin

Function: provides an interface for managing table information of hbase databases. It provides the following methods: Create a table, delete a table, List table items, make the table valid or invalid, and add or delete table columnfamily members.

Return Value	Function	Description
Void	AddColumn (string tablename, hcolumndescriptor column)	Add an existing table
	Checkhbaseavailable (hbaseconfiguration conf)	Static function to check whether hbase is running
	Createtable (htabledescriptor DESC)	Create a table for synchronization
	Deletetable (byte [] tablename)	Delete an existing table
	Enabletable (byte [] tablename)	Make the table valid
	Disabletable (byte [] tablename)	Make the table invalid
Htabledescriptor []	Listtables ()	List all user controls
Void	Modifytable (byte [] tablename, htabledescriptor htd)	It may take some time to modify the table mode, which is an asynchronous operation.
Boolean	Tableexists (string tablename)	Check whether the table exists

Usage example:

HBaseAdmin admin = new HBaseAdmin(config);admin.disableTable("tablename")

3. htabledescriptor

Link: org. Apache. hadoop. hbase. htabledescriptor

Function: contains the columnfamily of the table whose names are extremely matched.

Return Value	Function	Description
Void	Addfamily (hcolumndescriptor)	Add a columnfamily
Hcolumndescriptor	Removefamily (byte [] column)	Remove a columnfamily
Byte []	Getname ()	Get the table name
Byte []	Getvalue (byte [] key)	Get Attribute Value
Void	Setvalue (string key, string value)	Set attribute values

Usage example:

HTableDescriptor htd = new HTableDescriptor(table);htd.addFamily(new HcolumnDescriptor("family"));

In the preceding example, an hcolumndescriptor instance is used to add a columnfamily for the htabledescriptor.

Iv. hcolumndescriptor

Link: org. Apache. hadoop. hbase. hcolumndescriptor

Purpose: maintain information about the column family, such as the version number and compression settings. It is usually used when creating a table or adding a column family to a table. After a column family is created, it cannot be directly modified. You can only delete it and recreate it. When a column family is deleted, the data in the column family is also deleted.

Return Value	Function	Description
Byte []	Getname ()	Obtains the name of a column family.
Byte []	Getvalue (byte [] key)	Get the value of the corresponding attribute
Void	Setvalue (string key, string value)	Set the value of the corresponding attribute

Usage example:

HTableDescriptor htd = new HTableDescriptor(tablename);HColumnDescriptor col = new HColumnDescriptor("content:");htd.addFamily(col);

In this example, a column family of content is added.

5. htable

Link: org. Apache. hadoop. hbase. Client. htable

Purpose: it can be used to directly communicate with hbase tables. This method is not thread-safe for update operations.

Return Value	Function	Description
Void	Checkadnput (byte [] row, byte [] family, byte [] qualifier, byte [] value, put	Automatically checks whether row/family/qualifier matches the specified value.
Void	Close ()	Release all resources or suspend updates in the internal buffer
Boolean	Exists (get)	Check whether the value specified by the get instance exists in the htable column.
Result	Get (get)	Obtains the values of certain cells in a specified row.
Byte [] []	Getendkeys ()	Obtains the end key value of each area of the currently opened table.
Resulttables	Getiterator (byte [] Family)	Obtains the region instance of the given columnfamily.
Htabledescriptor	Gettabledescriptor ()	Obtains the htabledescriptor instance of the current table.
Byte []	Gettablename ()	Get table name
Static Boolean	Istableenabled (hbaseconfiguration Conf, string tablename)	Check whether the table is valid
Void	Put (put)	Add value to table

Usage example:

HTable table = new HTable(conf, Bytes.toBytes(tablename));ResultScanner scanner =  table.getScanner(family);

Vi. Put

Link: org. Apache. hadoop. hbase. Client. Put

Role: Used to add a single row

Return Value	Function	Description
Put	Add (byte [] family, byte [] qualifier, byte [] value)	Add the specified column and corresponding value to the put instance.
Put	Add (byte [] family, byte [] qualifier, long ts, byte [] value)	Add the specified column, corresponding value, and timestamp to the put instance.
Byte []	Getrow ()	Get Put instance rows
Rowlock	Getrowlock ()	Get the row lock of the put instance
Long	Gettimestamp ()	Obtain the time stamp of the put instance.
Boolean	Isempty ()	Check whether familymap is empty
Put	Settimestamp (long timestamp)	Set the time stamp of the put instance

Usage example:

Htable table = new htable (Conf, bytes. tobytes (tablename); Put P = new put (brow); // create a put Operation P for the specified row. add (family, qualifier, value); table. put (P );

VII. Get

Link: org. Apache. hadoop. hbase. Client. Get

Function: used to obtain information about a single row.

Return Value	Function	Description
Get	AddColumn (byte [] family, byte [] qualifier)	Obtains the columns corresponding to the specified column family and column modifier.
Get	Addfamily (byte [] Family)	Obtains all columns of the corresponding columns through the specified column family.
Get	Settimerange (long minstamp, long maxstamp)	Obtains the version number of the specified pickup column.
Get	Setfilter (filter)	Set the server-side filter when performing the get operation.

Usage example:

HTable table = new HTable(conf, Bytes.toBytes(tablename));Get g = new Get(Bytes.toBytes(row));

8. Result

Link: org. Apache. hadoop. hbase. Client. Result

Purpose: store the get or scan operation and obtain the single row value of the table. The methods provided by this class can be used to directly obtain values or various map structures (key-value pairs)

Return Value	Function	Description
Boolean	Containscolumn (byte [] family, byte [] qualifier)	Check whether the specified Column exists
Navigablemap <byte [], byte []>	Getfamilymap (byte [] Family)	Obtains the key-value pairs of modifiers and values contained in the corresponding columnfamily.
Byte []	Getvalue (byte [] family, byte [] qualifier)	Obtain the latest value of the corresponding column

9. resulttables

Link: Interface

Function: interface for obtaining value from the client

Return Value	Function	Description
Void	Close ()	Close the allocate and release the resources allocated to it.
Result	Next ()	Get the value of the next row