JSON-RPC Objects

JSON-RPC Objects is complete implementation of by JSON-RPC defined objects with respect to specifications compliance and API backward compatibility. It implements all versions of the protocol and support for ability to communicate by the same protocol version which the other side uses by a transparent way.

It means, it implements following JSON-RPC versions:

• 1.0 (original specification)
• 1.1 WD (working draft)
• 1.1 Alt (alternative proposal)
• 2.0 (revised specification proposal)

All protocols are implemented from point of view of features which must complain to. Some of these features aren't encouraged to use, but it's on will of the user. 2.0 and 1.1 Alt implement some minor additions in comparing to specification such as object extensions as defined in 1.1 WD, but mainly because of API compatibility and functionallity reasons.

All classes inherit from previous protocol version classes so API is homogenous. Application which can deal with 1.0 can deal with 2.0 too without any funcionallity or logic lost.

All object classes have three creating class methods:

• #create(<some arguments>, opts = { }) – which creates new object according to arguments (required members) and options (optional members),
• #parse(string) – which parses the JSON string,
• #new(data) – which creates new object from hash.

All names of both class names and optional arguments are exactly the same as defined in specification.

Library can be used by two ways. You know either concrete version of the protocol which you want to use in your application (typically client) or you process some incoming request which can use whatever of the versions (typically server).

Concrete version use example (creates call to subtract method with ID "a2b3"):

require "json-rpc-objects/v10/request"
require "json-rpc-objects/v11/alt/request"
require "json-rpc-objects/v20/request"

JsonRpcObjects::V10::Request::create(:subtract, ["1", "2"], :id => "a2b3")
JsonRpcObjects::V11::Alt::Request::create(:subtract, ["1", "2"], :id => "a2b3")
JsonRpcObjects::V20::Request::create(:subtract, ["1", "2"], :id => "a2b3")

Or incoming data processing request:

require "json-rpc-objects/request"
JsonRpcObjects::Request::parse(string)

…which will simply return request object of appropriate class according to its version. Be warn, to distinguish between 1.1 Alt and 1.1 WD is impossible in most of cases. It isn't problem for simple use, but it can be problem in some special cases. Default is WD, but Alt can be set as default if it's required.

In some cases, for example in case implementing of JSON-RPC server, you need make response to request by the same protocol version. It can be achieved by simple way:

require "json-rpc-objects/request"

request = JsonRpcObjects::Request::parse(string)
# ... <data processing>
response = request.class::version.response::create(<some args>)

This code analyzes protocol version of the request and creates response of the same protocol version. It utilizes call handler, so you can call for example request.class::version.service_procedure_description::create(<arguments>) for obtaining 1.1 service procedure description object. But be warn, neither 1.0 nor 2.0 implements these objects, so it can simply cause LoadError in that case, therefore it really isn't recommended.

Be limited by Error, Request and Response classes here or check the protocol version using #VERSION class constant.

Multiple serializers support is implemented, so you aren't limited to JSON[8] only, but you can use also built-in serializer to Ruby marshaling format or serializers to YAML, BSON and others. At this time, the following serializer gems are available:

• json-rpc-objects-json – JSON using the multi_json gem for widespread compatibility,
• json-rpc-objects-yaml – YAML using the standard library Ruby Syck,
• json-rpc-objects-bson – BSON format of MongoDB,
• json-rpc-objects-msgpack – very fast MessagePack format,
• json-rpc-objects-psych – YAML using more modern libyaml library.

You can set the default serializer for whole library session (both class and instance of the class are supported):

require "json-rpc-objects/serializer/marshal"

JsonRpcObjects::default_serializer(JsonRpcObjects::Serializer::Marshal)

# it's setting default serializer for all new instances, without
# arguments it returns the default serializer

Or by individual object assigning (only instances are supported):

require "json-rpc-objects/serializer/marshal"

serializer = JsonRpcObjects::Serializer::Marshal::new
JsonRpcObjects::V10::Request::parse(data, serializer)

…and the same for constructor. The #serializer property is also accessible, both readable and writable on all objects. By the same way, serializer is received by the generic parsers JsonRpcObjects::Request and so too.

Copyright © 2011 – 2015 Martin Poljak. See LICENSE.txt for further details.