How to deserializes request in Apex using deserialize(jsonString, apexType)?

 deserialize(jsonString, apexType) deserializes the specified JSON string into an Apex object of the specified type.

Consider the below JSON for understanding the use of  deserialize(jsonString, apexType).

Let say we are receiving this JSON from external system and we want to write REST webservice to handle this request.

{ 

  "nameofsystem" : "ExternalSystem1",

  "event": {

    "recorddata": {

      "state": "Success",

      "recordItem": [

        {

          "id": "1",

          "name": "testRecord1"

        },

        {

          "id": "2",

          "name": "testRecord2"

        }

      ]

    }

  }

}

In webservice class,

@RestResource(urlMapping='/postrecorddata/*')

   global with sharing class postrecorddata {

       @HttpPost

      global static responseWrapper postrecorddatamethod(){

        RestRequest req = RestContext.request;

        RestResponse res = Restcontext.response;

        responeWrapper wrapObj= (responeWrapper) JSON.deserialize(req.requestbody.toString(),responeWrapper.class);

        // To get the the state from JSON response.

        String stateInResponse = wrapObj.event.recorddata.state;

        // Perform operations

        returnResponseWrapper obj=new returnResponseWrapper();

        obj.message='Data Posted successfully';

        obj.statusCode = '200';

        // Overriding RestResponse object value

        res.statusCode = '200';

        return obj;

        

      }

 

// Wrapper class for handling request

global class responeWrapper{

 global string nameofsystem;

 global eventData event;

 

}

global class eventData{

 global recorddataObj recorddata;

}

 

global class recorddataObj{

 global string state;

 global recordItemClass[] recordItem;

  

}

 

global class recordItemClass{

 global string id; 

 global string name;

}

// Wrapper class for handling request

 

// Wrapper class for response

      global class returnResponseWrapper{

        global string message;

        global integer statusCode;

        }

 

// Wrapper class for responde

 

}