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Revision 13 as of 2012-01-19 23:59:16
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= Introduction =
The Thrift type system is intended to allow programmers to use native types as much as possible, no matter what programming language they are working in. This information is based on, and supersedes, the information in the [[http://developers.facebook.com/thrift/thrift-20070401.pdf|Thrift Whitepaper]]. The [[ThriftIDL]] provides descriptions of the types which are used to generate code for each target language.

= Base Types =
The base types were selected with the goal of simplicity and clarity rather than abundance, focusing on the key types available in all programming languages.

'''{{{bool}}}''': A boolean value ({{{true}}} or {{{false}}})

'''{{{byte}}}''': An 8-bit signed integer

'''{{{i16}}}''': A 16-bit signed integer

'''{{{i32}}}''': A 32-bit signed integer

'''{{{i64}}}''': A 64-bit signed integer

'''{{{double}}}''': A 64-bit floating point number

'''{{{string}}}''': A text string encoded using UTF-8 encoding

Note the absence of unsigned integer types. This is due to the fact that there are no native unsigned integer types in many programming languages.

== Special Types ==
'''{{{binary}}}''': a sequence of unencoded bytes

 * N.B.: This is currently a specialized form of the {{{string}}} type above, added to provide better interoperability with Java. The current plan-of-record is to elevate this to a base type at some point.

= Structs =
Thrift structs define a common object -- they are essentially equivalent to classes in OOP languages, but without inheritance. A struct has a set of strongly typed fields, each with a unique name identifier. Fields may have various annotations (numeric field IDs, optional default values, etc.) that are described in the [[ThriftIDL]].

= Containers =
Thrift containers are strongly typed containers that map to commonly used and commonly available container types in most programming languages.

There are three container types:

 * '''{{{list<}}}''type''{{{>}}}''': An ordered list of elements. Translates to an STL {{{vector}}}, Java {{{ArrayList}}}, native arrays in scripting languages, etc.
 * '''{{{set<}}}''type''{{{>}}}''': An unordered set of unique elements. Translates to an STL {{{set}}}, Java {{{HashSet}}}, {{{set}}} in Python, etc. Note: PHP does not support sets, so it is treated similar to a List
 * '''{{{map<}}}''type1''{{{,}}}''type2''{{{>}}}''': A map of strictly unique keys to values. Translates to an STL {{{map}}}, Java {{{HashMap}}}, PHP associative array, Python/Ruby dictionary, etc.

While defaults are provided, the type mappings are not explicitly fixed. Custom code generator directives have been added to allow substitution of custom types in various destination languages.

Container elements may be of any valid Thrift type.

 * N.B.: For maximal compatibility, the key (type1) for {{{map}}} should be a basic type rather than a struct or mutable container type. Many languages do not support more complex key types in their native {{{map}}} types. Also, the JSON protocol only supports key types that are base types.

= Exceptions =
Exceptions are functionally equivalent to structs, except that they inherit from the native exception base class as appropriate in each target programming language, in order to seamlessly integrate with the native exception handling in a given language.

= Services =
Services are defined using Thrift types. Definition of a service is semantically equivalent to defining an interface (or a pure virtual abstract class) in object oriented programming. The Thrift compiler generates fully functional client and server stubs that implement the interface.

A service consists of a set of named functions, each with a list of parameters, a return type and a list of any exceptions that may be thrown/raised. Those exceptions are themselves thrift 'exception' types.

Note that {{{void}}} is a valid type for a function return, in addition to all other defined Thrift types. Additionally, the {{{oneway}}} modifier keyword (equal to the deprecated "async" modifier) may be added to a {{{void}}} function, which will generate client code that does not wait for a response from the server. Note that a pure {{{void}}} function ''will'' return an acknowledgement response to the client which indicates that the operation has completed on the server side. With {{{oneway}}} method calls, the client will only be guaranteed that the request succeeded at the transport layer, which does not guarantee that the server ever saw the message . {{{Async/oneway}}} method calls from a single client connection may be executed in parallel/out of order by the server.
Moved to http://thrift.apache.org/docs/types/

ThriftTypes (last edited 2012-05-04 01:31:47 by jfarrell)