JSON Module

The correct approach is to consider a json object as a hashtable ( you can put (key;value) pairs, and you can delete and get values by key) and a json array as an array ( you can append, delete and replace values).

Since the JSON format can have objects inside other objects you can have multiple nested hashtables or arrays and you can access these using paths.

1.2. Dependencies

1.2.1. OpenSIPS Modules

This module does not depend on other modules.

1.2.2. External Libraries or Applications

libjson The libjson C library can be downloaded from: http://oss.metaparadigm.com/json-c/

1.3. Exported Parameters

The module does not export any parameters.

1.4. Exported Pseudo-Variables

1.4.1. `$json(id)`

The json variable provides methods to access fields in json objects and indexes in json arrays.

1.4.1.1. Variable lifetime

The json variables will be available to the process that created them from the moment they were initialized. They will not reset per message or per transaction. If you want to use the on a per message basis you should initialize them each time.

1.4.1.2. Accessing the $json(id) variable

The grammar that describes the id is:

id = name(identifier)*

identifier = key | index

key = /string | /$var

index = [integer] | [$var] | []

The "[]" index represents appending to the array. It should only be used when trying to set a value and not when trying to get one.

Negative indexes can be used to access an array starting from the end. So "[-1]" signifies the last element.

IMPORTANT: The id strictly complies to this grammar. You should be careful when using spaces because they will NOT be ignored. This was done to allow keys that contain spaces.

Variables can be used as indexes or keys. Variables that will be used as indexes must contain integer values. Variables that will be used as keys should contain string values.

Trying to get a value from a non-existing path (key or value) will return the NULL value and notice messages will be placed in the log describing the value of the json and the path used.

Trying to replace or insert a value in a non-existing path will cause an error in setting the value and notice messages will be printed in the log describing the value of the json and the path used

Example 1.1. Accessing the $json variable

...
$json(obj1/key) = "value"; #replace or insert the (key,value)
			   #pair into the json object;
			   
$json(matrix1[1][2]) = 1;  #replace the element at index 2 in the element
			   #at index 1 in an array

xlog("$json(name/key1[0][-1]/key2)"); # a more complex example

...

Example 1.2. Iterating through an array using variables

...

$json(ar1) := "[1,2,3,4]";

$var(i) = 0;

while( $json(ar1[$var(i)]) )
{

	#print each value
	xlog("Found:[$json(ar1[$var(i)])]\n");

	#increment each value
	$json(ar1[$var(i)])  = $json(ar1[$var(i)]) + 1 ;

	$var(i) = $var(i) + 1;

}


...

1.4.1.3. Returned values from $json(id)

If the value specified by the id is an integer it will be returned as an integer value.

If the value specified by the id is a string it will be returned as a string.

If the value specified by the id is any other type of json ( null, boolean, object, array ) the serialized version of the object will be returned as a string value. Using this and the ":=" operator you can duplicate json objects and put them in other json objects ( for string or integer you may use the "=" operator).

If the id does not exist a NULL value will be returned.

1.4.1.4. Operators for the $json(id) variable

There are 2 operators available for this variable.

1.4.1.4.1. The "=" operator

This will cause the value to be taken as is and be added to the json object ( e.g. string value or integer value ).

Setting a value to NULL will cause it to be deleted.

Example 1.3. Appending integers to arrays

...
$json(array1[]) = 1;
...

Example 1.4. Deleting the last element in an array

...
$json(array1[-1]) = NULL;
...

Example 1.5. Adding a string value to a json object

...
$json(object1/some_key) = "some_value";
...

1.4.1.4.2. The ":=" operator

This will cause the value to be taken and interpreted as a json object ( e.g. this operator should be used to parse json inputs ).

Example 1.6. Initializing an array

...
$json(array1) := "[]";
...

Example 1.7. Setting a boolean or null value

...
$json(array1[]) := "null";
$json(array1[]) := "true";
$json(array1[]) := "false";
...

Example 1.8. Adding a json to another json

...

$json(array) := "[1,2,3]";
$json(object) := "{}";
$json(object/array) := $json(array) ;
...

1.4.2. `$json_pretty(id)`

The json_pretty variable has the same purpose as the json variable, but prints the JSON object in a pretty format, adding spaces and tabs to make the output more readable.

1.4.3. `$json_compact(id)`

The json_compact variable has the same purpose as the json variable, but prints the JSON object in a more compact form, without formatting spaces.

1.5. Exported Functions

1.5.1. `json_link("$json(dest_id)", "$json(source_id)")`

This function can be used to link json objects together. This will work simillar to setting a value to an object, the only difference is that the second object is not copied, only a reference is created.

Changes to any of the objects will be visible in both of them.

You can use this method either to create references so each time you access the field you don't have to go through the full path (for speed efficiency and shorter code), or if you have an object that must be added to many other objects and you don't want to copy it each time (space and speed efficiency).

You can think of this object exactly as a reference in an object-oriented language. Modifying fields referenced by the variable will cause modifications in all the objects, BUT modifying the variable itsef will not cause any changes to other objects.

WARNING: You should be carefull when using references. If you accidentally create a circular reference and try to get the value from the object you will crash OPENSIPS.

Example 1.9. Creating a reference

...

$json(b) := "[{},{},{}]";

json_link("$json(stub)","$json(b[0])");

$json(stub/ana) = "are"; #add to the stub
$json(stub/ar) := "[]";
$json(stub/ar[]) = 1;
$json(stub/ar[]) = 2;
$json(stub/ar[]) = 3;

$json(b[0]/ar[0]) = NULL; # delete from the original object

xlog("\nTest link :\n$json(stub)\n$json(b)\n\n");

/*Output:

Test link :
{ "ana": "are", "ar": [ 2, 3 ] }
[ { "ana": "are", "ar": [ 2, 3 ] }, { }, { } ]

*/

$json(stub) = NULL; #delete the stub, no change will happen to the source


xlog("\nTest link :\n$json(stub)\n$json(b)\n\n");

/* Output:

Test link :
<null>
[ { "ana": "are", "ar": [ 2, 3 ] }, { }, { } ]

*/





...

Example 1.10. [LOGICAL ERROR] Creating a circular reference

...

$json(b) := "[1]";

/* NEVER do this, it is meant only to show where problems might occur  */
json_link("$json(b[0])","$json(b)"); # replace 1 with a reference to b

xlog("\nTest link :\n$json(stub)\n$json(b)\n\n");

/* this will cause OPENSIPS to crash because it will continuously try
 to get b, then b[0], then b ... */


...

Chapter 2. Contributors

2.1. By Commit Statistics

Table 2.1. Top contributors by DevScore⁽¹⁾, authored commits⁽²⁾ and lines added/removed⁽³⁾

	Name	DevScore	Commits	Lines ++	Lines --
1.	Andrei Dragus	18	4	1556	12
2.	Liviu Chircu (@liviuchircu)	16	13	43	82
3.	Razvan Crainea (@razvancrainea)	14	11	48	76
4.	Bogdan-Andrei Iancu (@bogdan-iancu)	8	6	25	30
5.	Vlad Paiu (@vladpaiu)	5	3	29	11
6.	Björn Esser (@besser82)	4	2	124	44
7.	Ovidiu Sas (@ovidiusas)	4	2	17	4
8.	Vlad Patrascu (@rvlad-patrascu)	4	2	2	1
9.	Nick Altmann (@nikbyte)	3	1	47	15
10.	Anca Vamanu	3	1	3	1

All remaining contributors: Julián Moreno Patiño.

(1) DevScore = author_commits + author_lines_added / (project_lines_added / project_commits) + author_lines_deleted / (project_lines_deleted / project_commits)

(2) including any documentation-related commits, excluding merge commits. Regarding imported patches/code, we do our best to count the work on behalf of the proper owner, as per the "fix_authors" and "mod_renames" arrays in opensips/doc/build-contrib.sh. If you identify any patches/commits which do not get properly attributed to you, please submit a pull request which extends "fix_authors" and/or "mod_renames".

(3) ignoring whitespace edits, renamed files and auto-generated files

2.2. By Commit Activity

Table 2.2. Most recently active contributors⁽¹⁾ to this module

	Name	Commit Activity
1.	Razvan Crainea (@razvancrainea)	Feb 2012 - Sep 2019
2.	Liviu Chircu (@liviuchircu)	Oct 2013 - Nov 2018
3.	Vlad Patrascu (@rvlad-patrascu)	May 2017 - Oct 2018
4.	Bogdan-Andrei Iancu (@bogdan-iancu)	Dec 2010 - Jun 2018
5.	Nick Altmann (@nikbyte)	Jan 2018 - Jan 2018
6.	Björn Esser (@besser82)	Dec 2017 - Dec 2017
7.	Julián Moreno Patiño	Feb 2016 - Feb 2016
8.	Vlad Paiu (@vladpaiu)	Jul 2014 - May 2015
9.	Ovidiu Sas (@ovidiusas)	Mar 2013 - Mar 2013
10.	Anca Vamanu	Sep 2009 - Sep 2009

All remaining contributors: Andrei Dragus.

(1) including any documentation-related commits, excluding merge commits

Chapter 3. Documentation

3.1. Contributors

Last edited by: Liviu Chircu (@liviuchircu), Bogdan-Andrei Iancu (@bogdan-iancu), Nick Altmann (@nikbyte), Razvan Crainea (@razvancrainea), Andrei Dragus.