ikrs.json
Software
Jun 2013
Was ist JSON?
JSON steht für JavaScript Object Notation und bezeichnet eine Klasse von Zeichenketten, die konstante Javascript-Objekte beschreiben (in Javascript-Syntax, und es gibt keine Funktionen). Sie sind oft ein geeignetes Datenaustauschformat für kleinere Anwendungen, bei denen XML zu mächtig ist und unnötigen Overhead erzeugen würde.
Siehe auch die JSON-Spezifikation: http://www.ietf.org/rfc/rfc4627.txt
Was ist ikrs.json?
ikrs.json ist ein kleiner JSON-Parser und -Builder geschrieben in Java.
Folgende JSON-Typen werden erkannt:
- null
- Boolean
- Number
- String
- Array
- Object
Die Typen sind ineinander überführbar, sofern sie kompatibel sind, mittels der Methoden .asJSONNumber(), .asJSONArray(), .asJSONObject(), .asJSONString(), .asJSONBoolean().
Alle Typen implementieren das JSONValue-Interface.
Der JSON-Parser
Im Paket ikrs.json.parser liegen die Parser- und Builderklassen. Der JSONParser ist ein einfacher LALR(1)-Parser mit linearer Laufzeit. Während des Parseprozesses werden den erkannten Elementen entsprechende Event-Methoden aufgerufen, welche in der Parserklasse selbst jedoch Leermethoden sind. Unterklassen sollten die geerben Event-Methoden überschreiben.
Dies tut bereits der JSONBuilder. Er verarbeitet die ausgelösten Ereignisse und baut eine Datenstruktur, die die gelesense JSON-Datei/-Stream beschreibt und Zugriff auf die Entitäten ermöglicht. Das Ergebnis der Berechnung ist immer ein Objekt vom Typ JSONValue. Ob es sich um einen Array, eine Zahl, einen bool'schen Wert etc. handelt, verraten die Methoden .isArray(), .isNumber(), .isBoolean(), usw.
Eigentlich nichts neues, aber zum Lernen hat's getaugt :)
Download?
Klar!
https://github.com/IkarosKappler/ikrs.json
Lizenz?
GPLv2.0
README.md <<
Welcome to ikrs.json!
=====================
This software and all its components come under the General Public
License version 2.0 (GPL 2.0).
Feel free to copy and modify.
Author: Ikaros Kappler
Date: 2013-06-11
Modified: 2013-06-24 Ikaros Kappler (Added some security checks to the
JSONRPCHandler).
Version: 1.0.0
What is this?
-------------
ikrs.json is a Java package containing basic JSON classes (datatypes)
referring to the JSON specification as described in RFC 4627.
What is JSON?
-------------
JSON is the acronym for JavaScript Object Notation. All JSON strings
are fully valid Javascript codes and represent values such as boolean
values, numbers, undefined (null), strings, arrays and objects. By
this JSON covers mostly all simple types most programming languages
use.
JSON strings cannot contain executable code; they store just constant
values.
Due to the specification JSON values are defined as follows:
JSONValue := true | false | null | number | string | array | object
true := "true" (ASCII)
false := "false"
null := "null"
number := [ minus ] integer [ frac ] [ exponent ]
minus := "-"
integer := zero | DIGIT+
frac := "." DIGIT+
DIGIT := { zero , "1", "2", "3", "4", "5", "6", "7", "8", "9" }
zero := "0"
exponent := ( "e" | "E" ) [ minus | plus ] DIGIT+
string := [...] (see specs)
array := [...]
object := [...]
See http://www.ietf.org/rfc/rfc4627.txt for details.
Example
-------
{ "type" : "person",
"fist_name" : "Christopher",
"last_name" : "Lloyd",
"year_of_birth" : 1938,
"is_alive" : true,
"movie_ids" : [ 13, 17, 19, 23, 2 ],
"address" : { "street" : "Imaginary Rd. 31415",
"city" : "St. Olaf",
"zipcode" : 27182,
"country" : null
},
"id" : 12345
}
Package ikrs.json
-----------------
It contains the basic datatype classes:
- JSONValue (interface)
- AbstractJSONValue (abstract super class of all JSON types)
- JSONBoolean
- JSONNumber
- JSONString
- JSONArray
- JSONObject
- JSONNull
Package ikrs.json.parser
------------------------
This package contains a simple but fully functional JSON parser and some
builder classes/examples. The parser is a recursive LALR(1) parser and
has linear runtime O(n).
The main classes are:
- JSONParser
- JSONBuilder (an example builder class that demontrates how to build
up the JSON data structure on-the-fly. It's very
simple, so just take a look at the source ^^).
- JSONBuilderExample (this is a more enhanced builder example that
keeps track of all object member names and
array indices).
- JSONValueFactory (a factory class to create anonymous JSON values).
- ConfigurableJSONBuilder (this is the class of your choice: a
configurable JSON builder that uses a
customizable factory class).
A short example how to use the configurable JSON builder
--------------------------------------------------------
System.out.println( "Creating JSONValueFactory ... ");
JSONValueFactory factory = new DefaultJSONValueFactory();
System.out.println( "Initialising reader ... " );
Reader reader = new java.io.FileReader( "test.json.txt" );
System.out.println( "Initialising parser/builder ... " );
ConfigurableJSONBuilder b = new ConfigurableJSONBuilder( reader, false, factory );
System.out.println( "Starting the parser ..." );
long time_start = System.currentTimeMillis();
b.parse();
long time_end = System.currentTimeMillis();
System.out.println( "Closing the reader ..." );
reader.close();
System.out.println( "Done." );
System.out.println( "Parsing and building took " + (time_end - time_start) + " ms." );
JSONValue json = b.lastPoppedValue;
System.out.println( "JSON object: " + json.toString() );
The program's output is:
------------------------
Creating JSONValueFactory ...
Initialising reader ...
Initialising parser/builder ...
Starting the parser ...
Closing the reader ...
Done.
Parsing and building took 42 ms.
JSON object: ikrs.json.JSONObject={age=2630, answer_is_correct=false, error=this might be an error message., floating_value_0=0.0, floating_value_1=1.0, floating_value_2=1.3E23, mixed_array_and_object=ikrs.json.JSONArray=[A, B, ikrs.json.JSONObject={X=ikrs.json.JSONArray=[d, e]}, F], my_array=ikrs.json.JSONArray=[], my_array_2=ikrs.json.JSONArray=[1, 2, 3], my_array_3=ikrs.json.JSONArray=[1, false, ikrs.json.JSONObject={name=null}, true], my_parser_also_ignores_the_case=true, name=test, negative_float=-3.14159265359, negative_number=-23, nested_array_0=ikrs.json.JSONArray=[1, ikrs.json.JSONArray=[2, ikrs.json.JSONArray=[3, 4, 5], 6]], nested_object_0=ikrs.json.JSONObject={a=1, b=ikrs.json.JSONObject={c=2, d=ikrs.json.JSONObject={e=4, f=5}}, f=6}, object_0=ikrs.json.JSONObject={a=1, b=2, c=3, d=4}, question_expired=true, status=111, test_A=A line-
n -break, test_C=An unicode Å character (should be the danish Ao), test_x=false, test_y=testing, user_exists=true}
Package ikrs.json.rpc
---------------------
This package contains a set of JSON-RPC classes that provide server
side support for Remote Procedure Calls (RPCs).
Usually RPC requests are sent to a server over the network. Once the
request was processed (a method/function on the server was called with
some passed parameters) it generates a response which is sent back
to the caller.
JSON-RPC just uses JSON as an interchange language (protocol): a client
sends a JSON string to the server (the string describes the desired
method call) and the server sends its response as a JSON string too.
The most important classes are:
- JSONRPCHandler (a configurable JSON-RPC handler).
- JSONRPCRequest (the request class, a subclass of JSONValue).
- JSONRPCResponse (the response class, a subclass of JSONValue).
- RPCInvocationTarget (interface all RPC classes must implement if
the JSONRPCHandler should have access to
its methods).
Example
-------
System.out.println( "Creating JSONRPC ..." );
JSONRPCHandler rpc = new JSONRPCHandler();
rpc.addInvocationTarget( "x", new TestInvocationTarget(), true );
String requestString = "{'jsonrpc' : '2.0', 'method': 'doAnything', 'params' : [ 2, 'test_B', false ], 'id' : 1234 }";
System.out.println( "Executing the request ..." );
response = rpc.call( requestString );
System.out.println( "Response: " + response.toJSONString() );
Note that 'TestInvocationTarget' is an example class that implements the
RPCInvocationTarget interface and has only one method:
public void doAnything( int i, String s, boolean b )
That method simply prints the passed params on stdout.
The programs output would be:
Creating JSONRPC ...
Executing the request ...
DOING ANYTHING
integer param: 1
string param: test_A
boolean param: true
Response: { "error": null, "id": 1234, "jsonrpc": "2.0", "result": null }
Done.
Have fun!