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public abstract class HCatClient {

    /**
     * Creates an instance of HCatClient.
     *
     * @param conf An instance of configuration.
     * @return An instance of HCatClient.
     */
    public static HCatClient create(Configuration conf){
         return null;
    }

    /**
     * Get all existing databases that match the given
     * pattern. The matching occurs as per Java regular expressions
     *
     * @param databasePattern
     *          java re pattern
     * @return list of database names
     * @throws HCatException
     */
    public abstract List<String> listDatabasesByPattern(String pattern) throws HCatException;

    /**
     * Gets the database.
     *
     * @param dbName The name of the database.
     * @return An instance of HCatDatabaseInfo.
     * @throws HCatException
     */
    public abstract HCatDatabase getDatabase(String dbName) throws HCatException;

    /**
     * Creates the database.
     *
     * @param dbInfo An instance of HCatCreateDBDesc.
     * @throws HCatException
     */
    public abstract void createDatabase(HCatCreateDBDesc dbInfo)
            throws HCatException;

    /**
     * Drops a database.
     *
     * @param dbName The name of the database to delete.
     * @param ifExists Hive returns an error if the database specified does not exist,
     *                 unless ifExists is set to true.
     * @param mode This is set to either "restrict" or "cascade". Restrict will
     *             remove the schema if all the tables are empty. Cascade removes
     *             everything including data and definitions.
     * @throws HCatException
     */
    public abstract void dropDatabase(String dbName, boolean ifExists, String mode) throws HCatException;

    /**
     * Returns all existing tables from the specified database which match the given
     * pattern. The matching occurs as per Java regular expressions.
     * @param dbName
     * @param tablePattern
     * @return list of table names
     * @throws HCatException
     */
    public abstract List<String> listTablesByPattern(String dbName, String tablePattern)
            throws HCatException;

    /**
     * Gets the table.
     *
     * @param dbName The name of the database.
     * @param tableName The name of the table.
     * @return An instance of HCatTableInfo.
     * @throws HCatException
     */
    public abstract HCatTable getTable(String dbName, String tableName)
            throws HCatException;

    /**
     * Creates the table.
     *
     * @param createTableDesc An instance of HCatCreateTableDesc class.
     * @throws HCatException the h cat exception
     */
    public abstract void createTable(HCatCreateTableDesc createTableDesc)
            throws HCatException;

    /**
     * Creates the table like an existing table.
     *
     * @param dbName The name of the database.
     * @param existingTblName The name of the existing table.
     * @param newTableName The name of the new table.
     * @param ifExists the if exists
     * @param isExternal Set to "true", if table has be created at a different
     *                   location other than default.
     * @param location The location for the table.
     * @throws HCatException
     */
    public abstract void createTableLike(String dbName, String existingTblName,
            String newTableName, boolean ifExists, boolean isExternal,
            String location) throws HCatException;

    /**
     * Drop table.
     *
     * @param dbName The name of the database.
     * @param tableName The name of the table.
     * @param ifExists Hive returns an error if the database specified does not exist,
     *                 unless ifExists is set to true.
     * @throws HCatException
     */
    public abstract void dropTable(String dbName, String tableName,
            boolean ifExists) throws HCatException;

    /**
     * Renames a table.
     *
     * @param dbName The name of the database.
     * @param oldName The name of the table to be renamed.
     * @param newName The new name of the table.
     * @throws HCatException
     */
    public abstract void renameTable(String dbName, String oldName, String newName) throws HCatException;

    /**
     * Gets all the partitions.
     *
     * @param dbName The name of the database.
     * @param tblName The name of the table.
     * @return A list of partition names.
     * @throws HCatException the h cat exception
     */
    public abstract List<HCatPartition> getPartitions(String dbName, String tblName)
            throws HCatException;

    /**
     * Gets the partition.
     *
     * @param dbName The database name.
     * @param tableName The table name.
     * @param partitionName The partition name, Comma separated list of col_name='value'.
     * @return An instance of HCatPartitionInfo.
     * @throws HCatException
     */
    public abstract HCatPartition getPartition(String dbName, String tableName,
            String partitionName) throws HCatException;

    /**
     * Adds the partition.
     *
     * @param partInfo An instance of HCatAddPartitionDesc.
     * @throws HCatException the h cat exception
     */
    public abstract void addPartition(HCatAddPartitionDesc partInfo) throws HCatException;

    /**
     * Drops partition.
     *
     * @param dbName The database name.
     * @param tableName The table name.
     * @param partitionName The partition name, Comma separated list of col_name='value'.
     * @param ifExists Hive returns an error if the partition specified does not exist, unless ifExists is set to true.
     * @throws HCatException
     */
    public abstract void dropPartition(String dbName, String tableName,
            String partitionName, boolean ifExists) throws HCatException;

    /**
     * List partitions by filter.
     *
     * @param dbName The database name.
     * @param tblName The table name.
     * @param filter The filter string,
     *    for example "part1 = \"p1_abc\" and part2 <= "\p2_test\"". Filtering can
     *    be done only on string partition keys.
     * @return list of partitions
     * @throws HCatException the h cat exception
     */
    public abstract List<HCatPartition> listPartitionsByFilter(String dbName, String tblName,
            String filter) throws HCatException;

    /**
     * Mark partition for event.
     *
     * @param dbName The database name.
     * @param tblName The table name.
     * @param partKVs the part k vs
     * @param eventType the event type
     * @throws HCatException the h cat exception
     */
    public abstract void markPartitionForEvent(String dbName, String tblName,
            Map<String, String> partKVs, PartitionEventType eventType)
            throws HCatException;

    /**
     * Checks if is partition marked for event.
     *
     * @param dbName the db name
     * @param tblName the tbl name
     * @param partKVs the part k vs
     * @param eventType the event type
     * @return true, if is partition marked for event
     * @throws HCatException the h cat exception
     */
    public abstract boolean isPartitionMarkedForEvent(String dbName, String tblName,
            Map<String, String> partKVs, PartitionEventType eventType)
            throws HCatException;

    /**
     * Gets the delegation token.
     * @param renewerKerberosPrincipalName the renewer kerberos principal name
     * @return the delegation token
     * @throws HCatException the h cat exception
     */
    public abstract String getDelegationToken(String renewerKerberosPrincipalName) throws
        HCatException;

    /**
     * Renew delegation token.
     *
     * @param tokenStrForm the token str form
     * @return the long
     * @throws HCatException the h cat exception
     */
    public abstract long renewDelegationToken(String tokenStrForm) throws HCatException;

    /**
     * Cancel delegation token.
     *
     * @param tokenStrForm the token str form
     * @throws HCatException the h cat exception
     */
    public abstract void cancelDelegationToken(String tokenStrForm) throws HCatException;

}   
HCatCreateTableDesc

This class is a sub class of HCatCommandDesc and will be used by the users to create descriptor and validate it for the "create table" command.

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This class is a sub class of HCatCommandDesc and will be used by the users to create descriptors and validate it for the "create database" command.

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HCatAddPartitionDesc

This class is a sub class of HCatCommandDesc and will be used by the users to create descriptors and validate it for the "add partition" command.

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HCatTable

This class encapsulates the table information returned the HCatClient implementation class and provides a uniform view to the user.

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Code Block
 Configuration config = new Configuration();
 config.add("hive-site.xml");
 HCatClient client = HCatClient.create(config);
 ArrayList<HCatFieldSchema> cols = new ArrayList<HCatFieldSchema>();
 cols.add(new HCatFieldSchema("col1", Type.INT, "comment1"));
 cols.add(new HCatFieldSchema("col2", Type.STRING, "comment2"));
HCatCreateTableDesc desc = new HCatCreateTableDesc.Builder("default","demo_table").setFileFormatfileFormat("rcfile").setColscols(cols).build();

 boolean success = client.createTable(desc);

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