How to generate a Listed JSON from multiple Salesforce Objects(say account and contact) and send data in JSON format to mobile client without nesting Using REST API

Sometimes there is a request for listed JSON .Say we have two objects Accounts and Contacts and we have requirement not to nest the response instead send as a collection with key for list of Accounts as Account and key for Contact as Contact.

Below is the JSON format thats expected output,

{
    "Accounts": [
        {
            "attributes": {
                "type": "Account",
                "url": "/services/data/v25.0/sobjects/Account/001W0000006XDG9IAO"
            },
            "CreatedDate": "2012-08-09T08:29:43.000+0000",
            "LastModifiedDate": "2012-08-09T15:24:42.000+0000",
            "IsDeleted": true,
            "Id": "001W0000006XDG9IAO"
        },
        {
            "attributes": {
                "type": "Account",
                "url": "/services/data/v25.0/sobjects/Account/001W0000006XGEuIAO"
            },
            "CreatedDate": "2012-08-09T15:44:29.000+0000",
            "LastModifiedDate": "2012-08-09T15:50:31.000+0000",
            "IsDeleted": false,
            "Id": "001W0000006XGEuIAO"
        },
        {
            "attributes": {
                "type": "Account",
                "url": "/services/data/v25.0/sobjects/Account/001W0000006QtKyIAK"
            },
            "Phone": "12131",
            "CreatedDate": "2012-08-02T14:46:48.000+0000",
            "LastModifiedDate": "2012-08-09T15:43:20.000+0000",
            "IsDeleted": true,
            "Id": "001W0000006QtKyIAK"
        },
        {
            "attributes": {
                "type": "Account",
                "url": "/services/data/v25.0/sobjects/Account/001W0000006XGI4IAO"
            },
            "CreatedDate": "2012-08-09T15:50:07.000+0000",
            "LastModifiedDate": "2012-08-14T11:33:05.000+0000",
            "FirstName": "Test",
            "IsDeleted": false,
            "Id": "001W0000006XGI4IAO",
            "LastName": "Thomas"
        },
        {
            "attributes": {
                "type": "Account",
                "url": "/services/data/v25.0/sobjects/Account/001W0000006XGIDIA4"
            },
            "CreatedDate": "2012-08-09T15:44:55.000+0000",
            "LastModifiedDate": "2012-08-14T10:15:39.000+0000",
            "FirstName": "shgdshg",
            "IsDeleted": false,
            "Id": "001W0000006XGIDIA4",
            "LastName": "Hello"
        },
        {
            "attributes": {
                "type": "Account",
                "url": "/services/data/v25.0/sobjects/Account/001W0000006XGhwIAG"
            },
            "CreatedDate": "2012-08-09T16:08:14.000+0000",
            "LastModifiedDate": "2012-08-09T16:08:19.000+0000",
            "FirstName": "deleted",
            "IsDeleted": true,
            "Id": "001W0000006XGhwIAG",
            "LastName": "check"
        },

"Contacts": [
        {
            "attributes": {
                "type": "Contact",
                "url": "/services/data/v25.0/sobjects/Contact/003W0000007mNoqIAE"
            },
            "AccountId": "001W0000006XGI4IAO",
            "HCP__c": "001W0000006XGIDIA4",
            "FirstName": "Test",
            "IsDeleted": false,
            "Id": "003W0000007mNoqIAE",
            "LastName": "Thomas"
        },
        {
            "attributes": {
                "type": "Contact",
                "url": "/services/data/v25.0/sobjects/Contact/003W0000007mNp1IAE"
            },
            "AccountId": "001W0000006XGIDIA4",
            "HCP__c": "001W0000006XGEuIAO",
            "FirstName": "shgdshg",
            "IsDeleted": false,
            "Id": "003W0000007mNp1IAE",
            "LastName": "Hello"
        },
        {
            "attributes": {
                "type": "Contact",
                "url": "/services/data/v25.0/sobjects/Contact/003W0000007mNpGIAU"
            },
            "Phone": "3213",
            "AccountId": "001W0000006XGEuIAO",
            "HCP__c": "001W0000006XGIDIA4",
            "IsDeleted": false,
            "Id": "003W0000007mNpGIAU",
            "LastName": "ueiru"
        },
        {
            "attributes": {
                "type": "Contact",
                "url": "/services/data/v25.0/sobjects/Contact/003W0000007wAkwIAE"
            },
            "Phone": "206-999-1111",
            "AccountId": "001W0000006XJ3fIAG",
            "Email": "mwells@ubermind.com",
            "HCP__c": "001W0000006XGIDIA4",
            "FirstName": "Mark",
            "IsDeleted": false,
            "Id": "003W0000007wAkwIAE",
            "LastName": "Wells"
        }
]}

For this we will have to use customized wrapping ,

Following is the source code that will automatically handle the generation of JSON in the expected format,

global class SFA_AccountContactListedResponse{
 //Wrapper class to warp the various  List as Super wrapper
 global class supersobjectWrapper{
List Accounts=new List();//A list to hold the Accounts
List Contacts=new List();//A list to hold the Contacts  
}
//This method will be called as the http get request
public static supersobjectWrapper makeResponseString(){  
List  lstacc=new List();
List lstcontacts=new List();
lstacc=[Select Id,CreatedDate,LastModifiedDate,Isdeleted from Acccount ];
lstcontacts=[Select id,CreatedDate,LastModifiedDate,Isdeleted from Contact];
supersobjectWrapper superWrap=new supersobjectWrapper();//Instantiating thesuperclass
superWrap.Contacts= lstcontacts ;
superWrap.Accounts= lstacc;
return superWrap;
 }
}

The above class will be called as REST API using GET HTTP call,

@RestResource(urlMapping='/GetAcc/*')
global with sharing class SFA_ListedJsonGenerator{ 
@HttpGet
global static SFA_AccountGroupSyncManagerRevised.supersobjectWrapper returnJsonpacket(){ 
RestRequest req = RestContext.request;
SFA_AccountGroupSyncManagerRevised.supersobjectWrapper result;  
result=SFA_AccountContactListedResponse.supersobjectWrapper;
return result;
    }
}