org.wali

Interface SerDe<T>

Type Parameters:

T - the type of record that is to be Serialized and De-Serialized by this object

All Known Implementing Classes:

DummyRecordSerde, RepositoryRecordSerde, SchemaRepositoryRecordSerde, StateMapSerDe, WriteAheadRepositoryRecordSerde

public interface SerDe<T>

A mechanism for Serializing and De-Serializing a Record of a given Type

Method Summary

Modifier and Type	Method and Description
default void	close() Closes any resources that the SerDe is holding open
T	deserializeEdit(java.io.DataInputStream in, java.util.Map<java.lang.Object,T> currentRecordStates, int version) Reads an Edit Record from the given DataInputStream and merges that edit with the current version of the record, returning the new, merged version.
T	deserializeRecord(java.io.DataInputStream in, int version) Reads a Record from the given DataInputStream and returns this record.
java.lang.String	getLocation(T record) Returns the external location of the given record; this is used when a record is moved away from WALI or is being re-introduced to WALI.
java.lang.Object	getRecordIdentifier(T record) Returns the unique ID for the given record
UpdateType	getUpdateType(T record) Returns the UpdateType for the given record
int	getVersion() Returns the version that this SerDe will use when writing.
default void	readHeader(java.io.DataInputStream in) Provides the SerDe the opportunity to read header information before deserializing any records
void	serializeEdit(T previousRecordState, T newRecordState, java.io.DataOutputStream out) Serializes an Edit Record to the log via the given DataOutputStream.
void	serializeRecord(T record, java.io.DataOutputStream out) Serializes a Record in a form suitable for a Snapshot via the given DataOutputStream.
default void	writeHeader(java.io.DataOutputStream out) Provides the SerDe a chance to write header information to the given output stream

Method Detail

writeHeader

default void writeHeader(java.io.DataOutputStream out)
                  throws java.io.IOException

Provides the SerDe a chance to write header information to the given output stream

Parameters:

out - the DataOutputStream to write to

Throws:

java.io.IOException - if unable to write to the OutputStream

serializeEdit

void serializeEdit(T previousRecordState,
                   T newRecordState,
                   java.io.DataOutputStream out)
            throws java.io.IOException

Serializes an Edit Record to the log via the given DataOutputStream.

Parameters:

previousRecordState - previous state

newRecordState - new state

out - stream to write to

Throws:

java.io.IOException - if fail during write

serializeRecord

void serializeRecord(T record,
                     java.io.DataOutputStream out)
              throws java.io.IOException

Serializes a Record in a form suitable for a Snapshot via the given DataOutputStream.

Parameters:

record - to serialize

out - to write to

Throws:

java.io.IOException - if failed to write

readHeader

default void readHeader(java.io.DataInputStream in)
                 throws java.io.IOException

Provides the SerDe the opportunity to read header information before deserializing any records

Parameters:

in - the InputStream to read from

Throws:

java.io.IOException - if unable to read from the InputStream

deserializeEdit

T deserializeEdit(java.io.DataInputStream in,
                  java.util.Map<java.lang.Object,T> currentRecordStates,
                  int version)
           throws java.io.IOException

Reads an Edit Record from the given DataInputStream and merges that edit with the current version of the record, returning the new, merged version. If the Edit Record indicates that the entity was deleted, must return a Record with an UpdateType of UpdateType.DELETE. This method must never return null.

Parameters:

in - to deserialize from

currentRecordStates - an unmodifiable map of Record ID's to the current state of that record

version - the version of the SerDe that was used to serialize the edit record

Returns:

deserialized record

Throws:

java.io.IOException - if failure reading

deserializeRecord

T deserializeRecord(java.io.DataInputStream in,
                    int version)
             throws java.io.IOException

Reads a Record from the given DataInputStream and returns this record. If no data is available, returns null.

Parameters:

in - stream to read from

version - the version of the SerDe that was used to serialize the record

Returns:

record

Throws:

java.io.IOException - failure reading

getRecordIdentifier

java.lang.Object getRecordIdentifier(T record)

Returns the unique ID for the given record

Parameters:

record - to obtain identifier for

Returns:

identifier of record

getUpdateType

UpdateType getUpdateType(T record)

Returns the UpdateType for the given record

Parameters:

record - to retrieve update type for

Returns:

update type

getLocation

java.lang.String getLocation(T record)

Returns the external location of the given record; this is used when a record is moved away from WALI or is being re-introduced to WALI. For example, WALI can be updated with a record of type UpdateType.SWAP_OUT that indicates a Location of file://tmp/external1 and can then be re-introduced to WALI by updating WALI with a record of type UpdateType.CREATE that indicates a Location of file://tmp/external1

Parameters:

record - to get location of

Returns:

location

getVersion

int getVersion()

Returns the version that this SerDe will use when writing. This used used when serializing/deserializing the edit logs so that if the version changes, we are still able to deserialize old versions

Returns:

version

close

default void close()
            throws java.io.IOException

Closes any resources that the SerDe is holding open

Throws:

java.io.IOException - if unable to close resources