Example. Il Signore degli Anelli, di John Ronald Reuel Tolkien,. Bompiani. Title.
Author di John Ronald Reuel Tolkien,. Bompiani. Editor ...
RPC OVER INTERNET
Web API: RPC over Internet • RPC calls mapped onto HTTP (GET or POST) • Synchronous call • Asynchronous call • with callbacks • External data representation • JSON (Java Simple Object Notation) • http://www.json.org/json-it.html
• XML
• Protocols • REST, SOAP, JSONP, JSON-RPC, XML-RPC,…
JSON
JSON • Two fundamental structures:
See JSON Lint
XML in a nutshell • XML (eXtensible Markup Language) is a language derived
from SGML (Standard Generalized Markup Language), from which HTML also derives. • The key notion in the markup language familty is a
markup, something that describes some aspect of the data • In
HTML markups define the appearance of the document, whereas in XML they define the meaning of the data
XML in a nutshell • An XML document is a tree • Data appear inside elements • An element not only contains the data itself but also
information describing the meaning of the data
Example Title
Author
Il Signore degli Anelli, di John Ronald Reuel Tolkien, Bompiani.
Editor
Example Book Title Author Editor
Elements
Il Signore degli Anelli John R. R. Tolkien Bompiani
Tips : Browser allows to see the structure of the document
Elements and attribute Data Il Signore degli Anelli
Attribute (key/value pair) Tag Il Signore degli Anelli
Well formed document
Valid document • Document that follows composition rules about the its
structure • Two solutions • Document Type Definition • Easier, less ‘powerfull’
• XML Schema • More complex, more powerfull
WFD and validation XML Document
Syntax check
Grammar
Semantic check
XML-RPC
Overview of XML-RPC • Data Model • Scalar • Struct • Array • Messages • Request message • Response message • Error message
Scalar types Tag
Type
Example
or
four-byte signed integer
-12
0 (false) or 1 (true)
1
string
hello world
double-precision signed floating point number
-12.214
date/time
base64-encoded binary
20101504T09:30:00
eW91IGNhbid0IHJlYWQgdGhpcyE=
Struct type lowerBound 18 upperBound 139
Array type 12 Egypt 0 -31
Request message • Root element: methodCall • contains a MethodName element and a params
element • MethodName contains the name of the procedure being called • Params is a list of values for the parameters
Example XXX 123 12.3
Example XXX 123 12.3
methodCall methodName XXX
params param
value
param
value
i4
123
double 12.3
Example Scuola XXX 123 12.3 methodCall params methodName param i4
param double
methodCall methodName XXX
params param
value
param
value
i4
123
double 12.3
Complete request message POST /xmlrpc HTTP 1.0 User-Agent: … Host: … Content-type: text/xml Content-length: .. Circle_Area 12.2
Reply message 1
Fault message faultCode 4 faultString Too many parameters.
JSON-RPC 2.0 • JSON-RPC is a stateless, transport agnostic, light-weight
remote procedure call (RPC) protocol • Much like XML-RPC • No formal grammar • Definition of request object and reply object
• New feature: batch requests, notification
Some example --> {"jsonrpc": "2.0", "method": "subtract", "params": [42, 23], "id": 1} {"jsonrpc": "2.0", "method": "subtract", "params": [23, 42], "id": 2} {"jsonrpc": "2.0", "method": "subtract", "params": {"subtrahend": 23, "minuend": 42}, "id": 3} {"jsonrpc": "2.0", "method": "subtract", "params": {"minuend": 42, "subtrahend": 23}, "id": 4} [ {"jsonrpc": "2.0", "method": "sum", "params": [1,2,4], "id": "1"}, {"jsonrpc": "2.0", "method": "notify_hello", "params": [7]}, {"jsonrpc": "2.0", "method": "subtract", "params": [42,23], "id": "2"}, {"foo": "boo"}, {"jsonrpc": "2.0", "method": "foo.get", "params": {"name": "myself"}, "id": "5"}, {"jsonrpc": "2.0", "method": "get_data", "id": "9"} ]
