Advanced Json

Advanced JSON Persistence Mapping, RPCs, Cross-Domain and More. Kris Zyp [email_address] www.xucia.com www.json.com

Overview Specifications - JSON JSONT JSONPath JSON Referencing JSON Schema JSON-RPC JSPON JSON-P Tools CrossSafe JSPON Browser Persevere

JSON Overview/History JSON born from JavaScript object and array initializer syntax {“property”:”value”, “number”:2, “boolean”:true, “oddNumbers”:[1,3,5]} XML vs JSON Strengths of each

About JSON JSON = { “size” : “compact”, “readable” : true, “purposes” : [“simple data structures”, ”object serialization”], “simple” : true, “easily parsed” : true }

XML… <?xml version="1.0" encoding="utf-8"?> <xml xmlns:ajson="http://www.xucia.com/ page/Advanced_JSON" > <size>bigger</size> <readable type=“boolean” expectation=“consumer defines booleans the same way I do”>true</readable> <purpose ambiguity=“Is this an array?”>Give semantic meaning to documents</purpose> <derived_from>SGML</derived_from> <legacy_uses>many</legacy_uses> </xml>

Interoperability Minimizing cost of communication. JSON has a lot of flexibility. Conventions don’t matter as much when we write the client & server, but will with mashups JSON Definitions help us to interoperate without having to create or understand custom JSON usage. Analogous to RSS, SOAP, and XHTML in the XML world.

Cross Domain JSON XHR Same Origin Policy Script tags can access cross site scripts Dynamic Script Tag Insertion How to know when it loads? How to know what was returned? Is JSON even a valid script?

JSONP http://bob.pythonmac.org/archives/2005/12/05/remote-json-jsonp/ Defines a parameter for defining a prefix for JSON returned in a script www.jsonsource.com/?callback=done done({“name”:”my json object”}) Yahoo, Flickr provide this for their webservices Unsecure used alone!

CrossSafe How to access cross-domain data securely? Proxy – Secure, but slower and more work. Dynamic Script Tags – Faster, more direct, but insecure, cross domain has full access to your JS environment. Alternate technologies – Flash, signed applets CrossSafe – Fast, direct access that is secure. Implements JSONRequest Specification Implements Subspace Approach Uses Dynamic Script Tag insertion in nested iframes with domain containment for sandboxing

CrossSafe Must use hostname.domain.com and make webservice.domain.com accessible Servers must support JSONP or other callback parameter JSONRequest.get(“http://www.yahoo.com/..”, function(id, value) { … } Defers to native implementation when available Show Demo: http://www.xucia.com/page/CrossSafe

JSONT http://goessner.net/articles/jsont/ Data: { "link" : { "uri" : "http://company.com" , "title" : "company homepage" }} Transformation: { "link" : "<a href=\"{link.uri}\">{link.title}</a>" } Result: <a href= "http://company.com" >company homepage</a>

Referencing Circular References Me = {“name”:”Kris Zyp”, “spouse” : {“name”:”Nikki Zyp”}} MyWife = Me.spouse; MyWife.spouse = Me; Multiples References to single objects list = [{“name”:”first”,”child”:{“name”:”the child”}}, {“name”:”second”}] list[1].child = list[0].child;

JSON Referencing www.json.com Scope Intramessage Circular References Multiple References Intermessage Cross-Domain references Reference Methods Path - ref: “$.prop[4]” ID - ref: “111”

JSON Referencing (Intramessage) www.json.com Reference Methods Conventions – in string, fixups, in object Path – use $ for JSON root (per JSONPath) [{“child”:{“name”:”the child”}}, {“child”:{“$ref”:”$[0].child”}}] ID [{“child”:{“id”:”1”,“name”:”the child”}}, {“child”:{“$ref”:”1”}}] Combine – {“$ref”:”1.name”}

JSON Referencing www.json.com Intermessage – must use ID referencing Intermessage {“id”:”1”,”name”:”first”, “ child”:{“id”:”3”,“name”:”the child”}} {“id”:”2”,”name”:”second”, “ child”:{“$ref”:”3”}} Remote References {“id”:”2”,”name”:”second”, “ child”:{“$ref”:”http://www.json.com/jsonObject”}} URL rules Use the standard HTML rules for relative URLs in context GET /users/2 {“id”:”2”,”name”:”john”,”group”:{“$ref”:”../groups/1”}}

Identification Circular References Me = {“id”:”kris”, “ name”:”Kris Zyp”, “ spouse”:{“id”:”nikki”, “ name”:”Nikki Zyp”: “ spouse”:{“$ref”:”kris”}}} Library available on json.com

JSPON www.jspon.org Background… RESTful approach for interaction and interoperability with persistent data Most JSON is used to describe persisted data Deals with complex data structures, modifications, and more JSPON = REST + JSON + Relative URLs for ids and references

JSPON Over HTTP Every id has an implicit (or explicit) URL using the standard relative URL approach References to ids can be used for unloaded values (lazy loading) REST service POST to an id/url to append to an object PUT to an id/url to change an object GET to an id/url to get an object DELETE to an id/url to delete an object

Identification GET http://mydomain.com/objects/myObj {“id”:”myObj” -> http://mydomain.com/objects/myObj “ name”:”my object”, “ moreInfo”: {“$ref”:”largeObject”}, -> http://mydomain.com/object/myObj “ crossSiteRef”: {“$ref”:”http://yourdomain.com/yourObj”}, -> http://yourdomain.com/yourObj “ user”: {“$ref”:”../users/1”}, -> http:// mydomain.com/object/myObj } Partial Graph Transfer/Lazy Loading Object Modification Cross Domain Object Trees

Persevere Server JSON Server Object database server Interaction through REST commands with JSON Queries through JSONPath JSPON id approach Supports JSONP JSON-RPC method calls Demo distributed calls later JSON Schema support

Persevere Server Exposes multiple data sources as JSON (JSPON): Internal OO Database SQL Databases (MySQL, HSQL, etc) XML files Data Centric Security Avoids application logic centric security Modular server – can be used with other servers

JSPON Object Browser Capable of browsing, modifying, and observing structural and access rules of data sources. Demo at: http://www.xucia.com/browser.html?id=dyna%2F100788

JSONPath XPath for JSON Influenced by XPath and E4X syntax, and traditional C/Java/JS property access syntax Examples: $.store.book[0].title -> What you think $..author -> Recursive search authors $.book[:4]  first four books $.book[?(@.price<10)] -> books under 10

JSON-RPC http://json-rpc.org/ Request method - A string containing the name of the method to be invoked. params - An array of objects to pass as arguments to the method. id - The request id. This can be of any type. It is used to match the response with the request that it is replying to.

JSON-RPC Response result - The object that was returned by the invoked method. This must be null in case there was an error invoking the method. error - An error object if there was an error invoking the method. It must be null if there was no error. id - This must be the same id as the request it is responding to.

JSON-RPC Example { "method": "echo", "params": ["Hello JSON-RPC"], "id": 1} { "result": "Hello JSON-RPC", "error": null, "id": 1}

Persevere Server Client/Server JavaScript Persistent Object Mapping Rhino Environment

JSON Schema http://www.json.com/json-schema-proposal/ Contract about valid data Influenced by XML Schema, Kwalify, RelaxNG, and ES4 Analogous to Classes in OO Languages or DTDs/Schemas in XML Defines requirements for JSON properties and other property attributes Uses Validation - data integrity Documentation Interaction UI generation (forms and code) Can be used on the client and server Compact Implementation

JSON Schema Example {“name”:{ “type”:”string”, “required”:true, “nullable”:false, “ length”:25, “description”:”Name of the person”}, “ age”:{ “type”:”number”, “minimum”:0, “maximum”:125} }

JSON Schema Example {“address”:{ “type”:{“street”:{“type”:”string”}, “state”:{“type”:”string”}}, “ description”:”Where they live”}, “ born”:{“type”:[“number”,”string”]} }

JSON Schema Example {“name”:”Kris Zyp” “ age”:30, “ spouse”:{“id”:”nikki”}, “ schema”:{“id”:”person”, “ name”:{“type”:”string”}, “ age”:{“type”:”number”}, “ spouse”:{“type”:{“$ref”:”person”}} // recursive def }}

Persevere JS Client Persistent object mapping with REST web services Orthogonal Persistence and Lazy Loading Capabilities Implements JSON-RPC Method Calls Implements Persistent JavaScript API: http://www.persistentjavascript.org Implements JSPON With Persevere Server – End to end JS

Example Usage of Persevere var result = pjs.load(“data or query id”); var object = result[1]; var value = object.prop; object.prop = “new value”; result.push({name:”new object/row”}) Array.remove(result,object); // or splice

What Did We Not Have to Write? doAjax… (break up into multiple slides) Request controller Do sql… API to learn… Almost zero, majority of operations are standard JavaScript

Persevere JS Client Capabilities Compared to Jester – Jester is perfect for RoR Robust and scalable Lazy loading Automatic and Explicit Transactions Designed for optimistic locking/merging Auto save/Orthogonality Integration with Strands for threading/continuations Bi-directional dynamic object and structure creation and modification

Demo Demonstration of CRUD application with customer database. Fits well with other JavaScript libraries

Persevere Persisted Applications Functions/Methods can be stored in the persisted object stores Applications can exist as persistent object graphs. Persevere server implements Persistent JavaScript on the server. Distributed Computing capable with other JSPON/RPC implementators. Transparent remote calls

Persisted Application & Distributed Computing Demonstration Customers Demo Find Primes Demo Reverse Ajax Inheritance

Thank you for your time See the presentation and links to projects at: www.xucia.com/page/AdvancedJSON Xucia Incorporation www.xucia.com www.json.com email: [email_address] Kris Zyp 503-806-1841

Advanced Json

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Advanced Json