Night Crue
JSON library based on JSMN lib
Dependents: ATT_WNCInterface_Info WNCInterface_HTTP_example NerfUS-Coord Mbed_Prototype_copy_4_INNO_day_15_6_2017 ... more
C++ JSON wrapper over JSMN lib (https://github.com/zserge/jsmn).
This C++ Class is a set of common tools/procedures as a C++ wrapper over JSMN JSON parser library. It is intended to provide the boiler-plate code, with intentions to reduce code clutter, in more of C++ fashion.
In contrast to original library, Json is intended to work strictly with valid JSON structures. Non-standard JSON structures should result in an error.
This class works explicitly on the indices returned by underlying JSMN library. In the scope of this class, its function parameters, return types, and documentation, the term 'index' will always mean the index of JSMN tokens, parsed by the Json constructor, unless and until explicitly mentioned otherwise.
Diff: Json.h
- Revision:
- 7:8aa4d0e98eb0
- Parent:
- 6:c1d2153da4ed
--- a/Json.h Mon Aug 15 22:52:37 2016 +0000
+++ b/Json.h Tue Aug 16 22:26:36 2016 +0000
@@ -43,6 +43,106 @@
* tokens, parsed by the Json constructor, unless and until explicitly mentioned
* otherwise.
*/
+
+ /*
+ Example:
+
+ Let's say we have to parse the samle JSON:
+
+ {
+ "team": "Night Crue",
+ "company": "TechShop",
+ "city": "San Jose",
+ "state": "California",
+ "country": "USA",
+ "zip": 95113,
+ "active": true,
+ "members":
+ [
+ {
+ "firstName": "John",
+ "lastName": "Smith",
+ "active": false,
+ "hours": 18.5,
+ "age": 21
+ },
+ {
+ "firstName": "Foo",
+ "lastName": "Bar",
+ "active": true,
+ "hours": 25,
+ "age": 21
+ },
+ {
+ "firstName": "Peter",
+ "lastName": "Jones",
+ "active": false
+ }
+ ]
+ }
+
+ which without the "white spaces" will look like: {"team":"Night Crue","company":"TechShop","city":"San Jose","state":"California","country":"USA","zip":95113,"active":true,"members":[{"firstName":"John","lastName":"Smith","active":false,"hours":18.5,"age":21},{"firstName":"Foo","lastName":"Bar","active":true,"hours":25,"age":21},{"firstName":"Peter","lastName":"Jones","active":false}]}
+
+ Anyways, this class doesn't care about the formatting of JSON, however, it
+ DOES care about the validity of JSON. So here's a sample code to parse and
+ extract values from this JSON structure.
+
+ @code
+
+ void main ()
+ {
+ // Note that the JSON object is 'escaped'. One doesn't get escaped JSON
+ // directly from the webservice, if the response type is APPLICATION/JSON
+ // Just a little thing to keep in mind.
+ const char * jsonSource = "{\"team\":\"Night Crue\",\"company\":\"TechShop\",\"city\":\"San Jose\",\"state\":\"California\",\"country\":\"USA\",\"zip\":95113,\"active\":true,\"members\":[{\"firstName\":\"John\",\"lastName\":\"Smith\",\"active\":false,\"hours\":18.5,\"age\":21},{\"firstName\":\"Foo\",\"lastName\":\"Bar\",\"active\":true,\"hours\":25,\"age\":21},{\"firstName\":\"Peter\",\"lastName\":\"Jones\",\"active\":false}]}";
+
+ Json json ( jsonSource, strlen ( jsonSource ) );
+
+ if ( !json.isValidJson () )
+ {
+ logError ( "Invalid JSON: %s", jsonSource );
+ return;
+ }
+
+ if ( json.type (0) != JSMN_OBJECT )
+ {
+ logError ( "Invalid JSON. ROOT element is not Object: %s", jsonSource );
+ return;
+ }
+
+ // Let's get the value of key "city" in ROOT object, and copy into
+ // cityValue
+ char cityValue [ 32 ];
+
+ logInfo ( "Finding \"city\" Key ... " );
+ // ROOT object should have '0' tokenIndex, and -1 parentIndex
+ int cityKeyIndex = json.findKeyIndexIn ( "city", 0 );
+ if ( cityKeyIndex == -1 )
+ {
+ // Error handling part ...
+ logError ( "\"city\" does not exist ... do something!!" );
+ }
+ else
+ {
+ // Find the first child index of key-node "city"
+ int cityValueIndex = json.findChildIndexOf ( cityKeyIndex, -1 );
+ if ( cityValueIndex > 0 )
+ {
+ const char * valueStart = json.tokenAddress ( cityValueIndex );
+ int valueLength = json.tokenLength ( cityValueIndex );
+ strncpy ( cityValue, valueStart, valueLength );
+ cityValue [ valueLength ] = 0; // NULL-terminate the string
+
+ //let's print the value. It should be "San Jose"
+ logInfo ( "city: %s", cityValue );
+ }
+ }
+
+ // More on this example to come, later.
+ }
+
+ @endcode
+ */
class Json
{
