co.cask.cdap.api.data.format

Class RecordFormat<FROM,TO>

java.lang.Object

co.cask.cdap.api.data.format.RecordFormat<FROM,TO>

Type Parameters:

FROM - the raw data to read from.

TO - object to format the data into.

@Beta
public abstract class RecordFormat<FROM,TO>
extends Object

Interface specifying how to read data in some format into java objects. A format implies at least a default schema, which may be as simple as a byte array.

Field Summary

Fields

Modifier and Type	Field and Description
protected Schema	schema

Constructor Summary

Constructors

Constructor and Description
RecordFormat()

Method Summary

Modifier and Type	Method and Description
protected void	configure(Map<String,String> settings) Configure the format with the given properties.
protected abstract Schema	getDefaultSchema() Get the default schema for the format.
Schema	getSchema() Get the schema of the format.
void	initialize(FormatSpecification formatSpecification) Initialize the format with the given desired schema and properties.
abstract TO	read(FROM input) Read data from the input format to the output type.
protected abstract void	validateSchema(Schema schema) Validate the given schema, throwing an exception if it is unsupported.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

schema

protected Schema schema

Constructor Detail

RecordFormat

public RecordFormat()

Method Detail

read

public abstract TO read(FROM input)
                 throws UnexpectedFormatException

Read data from the input format to the output type.

Parameters:

input - input object to read.

Returns:

formatted input.

Throws:

UnexpectedFormatException - if the input object could not be read because it is of an unexpected format.

getDefaultSchema

protected abstract Schema getDefaultSchema()

Get the default schema for the format. The default is used if no schema is provided in the call to initialize(FormatSpecification). Should return null if there is no default schema, meaning a schema must be provided during initialization of the format.

Returns:

the default schema for the format, or null if a schema must be provided to the format

validateSchema

protected abstract void validateSchema(Schema schema)
                                throws UnsupportedTypeException

Validate the given schema, throwing an exception if it is unsupported. It can be assumed that the input schema is not null and is a record of at least one field.

Parameters:

schema - the schema to validate for the format

Throws:

UnsupportedTypeException - if the schema not supported

initialize

public void initialize(@Nullable
                       FormatSpecification formatSpecification)
                throws UnsupportedTypeException

Initialize the format with the given desired schema and properties. Guaranteed to be called once before any other method is called.

Parameters:

formatSpecification - the specification for the format, containing the desired schema and settings

Throws:

UnsupportedTypeException - if the desired schema and properties are not supported

configure

protected void configure(Map<String,String> settings)

Configure the format with the given properties. Guaranteed to be called once before any call to read(Object) is made, and after a schema for the format has been set.

Parameters:

settings - the settings to configure the format with

getSchema

public Schema getSchema()

Get the schema of the format.

Returns:

the schema of the format.