O
- The "outer" (user-facing) Java typeI
- The "inner" (Cassandra-facing, intermediary) Java typepublic abstract class MappingCodec<O,I> extends TypeCodec<O>
TypeCodec
that maps a Java Pojo to another Java object that can in turn be
serialized into a CQL type. This can serve as a base for libraries dealing with Pojo mappings.
This codec can be seen as a convenience base class for libraries dealing with Pojo-to-Pojo
mappings, but it comes with a performance penalty: each Java object is serialized in two steps:
first to an intermediate object, and then to a ByteBuffer
, which means that each
serialization actually incurs in two potentially expensive operations being carried.
If such operations are really expensive, and your mapping library is capable of serializing
objects directly to ByteBuffer
s, consider writing your own codec instead of using this
one.
TypeCodec.AbstractCollectionCodec<E,C extends Collection<E>>, TypeCodec.AbstractMapCodec<K,V>, TypeCodec.AbstractTupleCodec<T>, TypeCodec.AbstractUDTCodec<T>, TypeCodec.PrimitiveBooleanCodec, TypeCodec.PrimitiveByteCodec, TypeCodec.PrimitiveDoubleCodec, TypeCodec.PrimitiveFloatCodec, TypeCodec.PrimitiveIntCodec, TypeCodec.PrimitiveLongCodec, TypeCodec.PrimitiveShortCodec
Modifier and Type | Field and Description |
---|---|
protected TypeCodec<I> |
innerCodec |
Constructor and Description |
---|
MappingCodec(TypeCodec<I> innerCodec,
Class<O> javaType) |
MappingCodec(TypeCodec<I> innerCodec,
TypeToken<O> javaType) |
Modifier and Type | Method and Description |
---|---|
O |
deserialize(ByteBuffer bytes,
ProtocolVersion protocolVersion)
Deserialize the given
ByteBuffer instance according to the CQL type handled by this
codec. |
protected abstract O |
deserialize(I value) |
String |
format(O value)
Format the given value as a valid CQL literal according to the CQL type handled by this codec.
|
O |
parse(String value)
Parse the given CQL literal into an instance of the Java type handled by this codec.
|
protected abstract I |
serialize(O value) |
ByteBuffer |
serialize(O value,
ProtocolVersion protocolVersion)
Serialize the given value according to the CQL type handled by this codec.
|
accepts, accepts, accepts, accepts, ascii, bigint, blob, cboolean, cdouble, cfloat, cint, counter, custom, date, decimal, duration, getCqlType, getJavaType, inet, list, map, set, smallInt, time, timestamp, timeUUID, tinyInt, toString, tuple, userType, uuid, varchar, varint
public ByteBuffer serialize(O value, ProtocolVersion protocolVersion) throws InvalidTypeException
TypeCodec
Implementation notes:
null
input as the equivalent of an
empty collection.
serialize
in class TypeCodec<O>
value
- An instance of T; may be null
.protocolVersion
- the protocol version to use when serializing bytes
. In most
cases, the proper value to provide for this argument is the value returned by ProtocolOptions.getProtocolVersion()
(which is the protocol version in use by the driver).ByteBuffer
instance containing the serialized form of TInvalidTypeException
- if the given value does not have the expected typepublic O deserialize(ByteBuffer bytes, ProtocolVersion protocolVersion) throws InvalidTypeException
TypeCodec
ByteBuffer
instance according to the CQL type handled by this
codec.
Implementation notes:
null
or a default value for the corresponding Java type, if
applicable;
null
; they should return
empty collections instead (the driver's default collection codecs all comply with this
rule).
ByteBuffer
should never be consumed by read operations that modify
its current position; if necessary, ByteBuffer.duplicate()
duplicate} it before
consuming.
deserialize
in class TypeCodec<O>
bytes
- A ByteBuffer
instance containing the serialized form of T; may be null
or empty.protocolVersion
- the protocol version to use when serializing bytes
. In most
cases, the proper value to provide for this argument is the value returned by ProtocolOptions.getProtocolVersion()
(which is the protocol version in use by the driver).InvalidTypeException
- if the given ByteBuffer
instance cannot be deserializedpublic O parse(String value) throws InvalidTypeException
TypeCodec
Implementors should take care of unquoting and unescaping the given CQL string where
applicable. Null values and empty Strings should be accepted, as well as the string "NULL"
; in most cases, implementations should interpret these inputs has equivalent to a
null
reference.
Implementing this method is not strictly mandatory: internally, the driver only uses it to parse the INITCOND when building the metadata of an aggregate function (and in most cases it will use a built-in codec, unless the INITCOND has a custom type).
parse
in class TypeCodec<O>
value
- The CQL string to parse, may be null
or empty.null
on a null input
.InvalidTypeException
- if the given value cannot be parsed into the expected typepublic String format(O value) throws InvalidTypeException
TypeCodec
Implementors should take care of quoting and escaping the resulting CQL literal where
applicable. Null values should be accepted; in most cases, implementations should return the
CQL keyword "NULL"
for null
inputs.
Implementing this method is not strictly mandatory. It is used:
BuiltStatement
for a detailed explanation of when
this happens);
QueryLogger
, if parameter logging is enabled;
AggregateMetadata.asCQLQuery(boolean)
;
toString()
implementation of some objects (UDTValue
, TupleValue
, and the internal representation of a ROWS
response), which may
appear in driver logs.
format
in class TypeCodec<O>
value
- An instance of T; may be null
.InvalidTypeException
- if the given value does not have the expected typeCopyright © 2012–2023. All rights reserved.