NetSDS::App::JSRPC3pm

Usage

        #!/usr/bin/env perl
        # JSON-RPC server
        
        use 5.8.0;
        use warnings;
        use strict;
        JServer->run();
        1;
        # Server application logic
        package JServer;
        use base 'NetSDS::App::JSRPC';
        # This method is available via JSON-RPC
        sub sum {
                my ($self, $param) = @_;
                return $$param[0] + $$param[1];
        }
        1;

Overview

"NetSDS::App::JSRPC" module implements framework for common JSON-RPC based server application. JSON-RPC is a HTTP based protocol providing remote procudure call (RPC) functionality using JSON for requests and responses incapsulation.

This implementation is based on NetSDS::App::FCGI module and expected to be executed as FastCGI or CGI application.

Diagram of class inheritance:

          [NetSDS::App::JSRPC] - JSON-RPC server
                   |
          [NetSDS::App::FCGI] - CGI/FCGI application
                   |
             [NetSDS::App] - common application
                   |
        [NetSDS::Class::Abstract] - abstract class

Both request and response are JSON-encoded strings represented in HTTP protocol as data of 'application/json' MIME type.

Application development

To develop new JSON-RPC server application you need to create application class inherited from "NetSDS::App::JSRPC":

It's just empty application:

        #!/usr/bin/env perl
        
        JSApp->run(
                conf_file => '/etc/NetSDS/jsonapp.conf'
        );
        package JSApp;
        use base 'NetSDS::App::JSRPC';
        1;

Alsoe you may want to add some specific code for application startup:

        sub start {
                my ($self) = @_;
                connect_to_dbms();
                query_for_external_startup_config();
                do_other_initialization();
        }

And of course you need to add methods providing necessary functions:

        sub send_sms {
                my ($self, $params) = @_;
                return $self->{kannel}->send(
                        from => $params{'from'},
                        to => $params{'to'},
                        text => $params{'text'},
                );
        }
        sub kill_smsc {
                my ($self, $params) = @_;
                # 1M of MT SM should be enough to kill SMSC!
                # Otherwise we call it unbreakable :-)
                for (my $i=1; $<100000000; $i++) {
                        $self->{kannel}->send(
                                %mt_sm_parameters,
                        );
                }
                if (smsc_still_alive()) {
                        return $self->error("Can't kill SMSC! Need more power!");
                }
        }

Advanced functionality

"NetSDS::App::JSRPC" module provides two methods that may be used to implement more complex logic than average RPC to one class.

can_method() - method availability checking

By default it is just wrapper around "UNIVERSAL::can" function. However it may be rewritten to check for methods in other classes or even construct necessary methods on the fly.

process_call() - method dispatching

By default it just call local class method with the same name as in JSON-RPC call. Of course it can be overwritten and process query in some other way.

This code describes logic of call processing:

        # It's not real code
        if (can_method($json_method)) {
                process_call($json_method, $json_params);
        }

For more details read documentation below.

Class API

new(%params) - class constructor

It's internally used constructor that shouldn't be used from application directly.

process() - main JSON-RPC iteration

This is internal method that implements JSON-RPC call processing.

can_method($method_name) - check method availability

This method allows to check if some method is available for execution. By default it use "UNIVERSAL::can" but may be rewritten to implement more complex calls dispatcher.

Paramters: method name (string)

Return true if method execution allowed, false otherwise.

Example:

        # Rewrite can_method() to search in other class
        sub can_method {
                my ($self, $method) = @_;
                return Other::Class->can($method);
        }

process_call($method, $params) - execute method call

Paramters: method name, parameters.

Returns parameters from executed method as is.

Example:

        # Rewrite process_call() to use other class
        sub process_call {
                my ( $self, $method, $params ) = @_;
                return Other::Class->$method($params);
        }

_request_parse($post_data) - parse HTTP POST

Paramters: HTTP POST data as string

Returns: request method, parameters, id

_make_result(%params) - prepare positive response

This is internal method for encoding JSON-RPC response string.

Paramters:

id - the same as request Id (see specification)

result - method result

Returns JSON encoded response message.

_make_error(%params) - prepare error response

Internal method implementing JSON-RPC error response.

Paramters:

id - the same as request Id (see specification)

code - error code (default is -32603, internal error)

message - error message

Returns JSON encoded error message

Examples

See "samples/app_jsrpc.fcgi" appliction.

Todo

1. Move error codes to constants to provide more clear code.

2. Implement objects/classes support.