@RestResource(urlMapping='/Account/*')
global with sharing class MyRestResource {
    @HttpGet
    global static Account getRecord() {
        RestRequest req=RestContext.request;
        RestResponse res=RestContext.response;
        String urlId=req.requestURI.subString(req.requestURI.lastIndexOf('/')+1);
        Account accountList=[SELECT Id,Name,Phone,Description,Rating FROM Account WHERE Id =:urlId];
        return accountList;
    }
}

public class MyFirstRestApi {
    public static void getAccount(){
        HttpRequest req=new HttpRequest();
        req.setEndpoint('https://login.salesforce.com/services/oauth2/token');
        req.setMethod('POST');
        String CLIENT_ID = '3MVG9fe4g9fhX0E7c0s6z5_ojYYqdlgULEYYd4azO4hjX2hlWYb4jaNMUX.fYNikWLjDEmG3YMURayF.ySmbh';
        String CLIENT_SECRET = '379438EC996D2345F3632774AA40F7DF0A63D004C02C9781CDE6DA6F1623D92A';
        String USERNAME = 'nainsi.verma@cloudanalogy.com';
        String PASSWORD = 'Nainsi420@ujaA865VERblPRkzjb1TOeetE';
        
        req.setBody('grant_type=password' + '&client_id='+CLIENT_ID + 
                    '&client_secret='+CLIENT_SECRET + '&username='+USERNAME + '&password='+PASSWORD);
        Http http=new Http();
        HttpResponse res=new HttpResponse();
        res=http.send(req);
        System.debug('response-->: '+res.getBody());
        Oauth objAuthInfo=(Oauth)JSON.deserialize(res.getBody(), Oauth.class);
        if(objAuthInfo.access_token!=null){
            HttpRequest req1=new HttpRequest();
            req1.setEndpoint('https://cloudanalogy-2dd-dev-ed.my.salesforce.com/services/apexrest/Account/');
            req1.setMethod('GET');
            req1.setHeader('Authorization','Bearer '+objAuthInfo.access_token);
            Http http1=new Http();
            HttpResponse res1=new HttpResponse();
            res1=http1.send(req1);
            System.debug('Status -->: '+res1.getStatusCode());
            System.debug('Account Info-->: '+res1.getBody());
            //  Oauth1 obj1=(Oauth1)JSON.deserialize(res.getBody(), Oauth1.class);
            Account obj1=(Account)JSON.deserialize(res1.getBody(), Account.class);
            obj1.id=null;
            insert obj1;
            System.debug('Account---->insert: : '+obj1);
        }
    }
    public class Oauth{
        public String access_token{get;set;}
        public String instance_url{get;set;}
        public String id{get;set;}
        public String token_type{get;set;} 
        public String issued_at{get;set;}
        public String signature{get;set;}
    }  
}