co.cask.cdap.format.io

Class StructuredRecordDatumReader

java.lang.Object

co.cask.cdap.format.io.StructuredRecordDatumReader

All Implemented Interfaces:

DatumReader<co.cask.cdap.api.data.format.StructuredRecord>

Direct Known Subclasses:

JsonStructuredRecordDatumReader

public class StructuredRecordDatumReader
extends Object
implements DatumReader<co.cask.cdap.api.data.format.StructuredRecord>

A DatumReader for reading StructuredRecord.

Constructor Summary

Constructors

Constructor and Description
StructuredRecordDatumReader()

Method Summary

Modifier and Type	Method and Description
protected Object	decode(Decoder decoder, co.cask.cdap.api.data.schema.Schema schema) Decodes a value based on the Schema.
protected Collection<?>	decodeArray(Decoder decoder, co.cask.cdap.api.data.schema.Schema elementSchema) Decodes an array with array element of a given Schema.
protected String	decodeEnum(Decoder decoder, co.cask.cdap.api.data.schema.Schema schema) Decodes a enum value based on the given Schema.
protected Map<?,?>	decodeMap(Decoder decoder, co.cask.cdap.api.data.schema.Schema keySchema, co.cask.cdap.api.data.schema.Schema valueSchema) Decodes a map.
protected co.cask.cdap.api.data.format.StructuredRecord	decodeRecord(Decoder decoder, co.cask.cdap.api.data.schema.Schema schema) Decodes a record.
protected Object	decodeUnion(Decoder decoder, co.cask.cdap.api.data.schema.Schema schema) Decodes a value from a union.
co.cask.cdap.api.data.format.StructuredRecord	read(Decoder decoder, co.cask.cdap.api.data.schema.Schema sourceSchema)

Methods inherited from class java.lang.Object

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

Constructor Detail

StructuredRecordDatumReader

public StructuredRecordDatumReader()

Method Detail

read

public co.cask.cdap.api.data.format.StructuredRecord read(Decoder decoder,
                                                          co.cask.cdap.api.data.schema.Schema sourceSchema)
                                                   throws IOException

Specified by:

read in interface DatumReader<co.cask.cdap.api.data.format.StructuredRecord>

Throws:

IOException

decode

protected final Object decode(Decoder decoder,
                              co.cask.cdap.api.data.schema.Schema schema)
                       throws IOException

Decodes a value based on the Schema.

Parameters:

decoder - The decoder to decode value from

schema - The schema of the value

Returns:

The decoded value

Throws:

IOException - If failed to decode

decodeEnum

protected String decodeEnum(Decoder decoder,
                            co.cask.cdap.api.data.schema.Schema schema)
                     throws IOException

Decodes a enum value based on the given Schema. This method reads an integer as the index in the enum schema. Sub-class can override this to have different behavior.

Parameters:

decoder - The decode to decode value from

schema - The Schema of the enum

Returns:

A String representation of the enum value

Throws:

IOException - If failed to decode

decodeArray

protected Collection<?> decodeArray(Decoder decoder,
                                    co.cask.cdap.api.data.schema.Schema elementSchema)
                             throws IOException

Decodes an array with array element of a given Schema. This method reads an integer as the size of a chunk, followed by reading that many array element using the element schema, following by reading the size of the next chunk, until it reads 0. Sub-class can override this to have different behavior.

Parameters:

decoder - The decode to decode value from

elementSchema - The Schema of the array elements

Returns:

A Collection containing all array elements

Throws:

IOException - If failed to decode

decodeMap

protected Map<?,?> decodeMap(Decoder decoder,
                             co.cask.cdap.api.data.schema.Schema keySchema,
                             co.cask.cdap.api.data.schema.Schema valueSchema)
                      throws IOException

Decodes a map. This method reads an integer as the size of a chunk, followed by reading that many key and value pairs using the key and value schema, following by reading the size of the next chunk, until it reads 0. Sub-class can override this to have different behavior.

Parameters:

decoder - The decode to decode value from

keySchema - The Schema of the map key

valueSchema - The Schema of the map value

Returns:

A Map containing all map entries

Throws:

IOException - If failed to decode

decodeRecord

protected co.cask.cdap.api.data.format.StructuredRecord decodeRecord(Decoder decoder,
                                                                     co.cask.cdap.api.data.schema.Schema schema)
                                                              throws IOException

Decodes a record. This method decode fields one by one based on the given record schema. Sub-class can override this to have different behavior.

Parameters:

decoder - The decode to decode value from

schema - The Schema of the record

Returns:

A StructuredRecord representing the record decoded

Throws:

IOException - If failed to decode

decodeUnion

protected Object decodeUnion(Decoder decoder,
                             co.cask.cdap.api.data.schema.Schema schema)
                      throws IOException

Decodes a value from a union. This method first decode an integer as the index in the union schema for the value schema, followed decoding the value using that schema.

Parameters:

decoder - The decode to decode value from

schema - The Schema of the union

Returns:

The value decoded

Throws:

IOException - If failed to decode