JSON Deserialize Error : Expected '[' at the beginning of List/Set

Question

Im trying to deserialize a JSON to object. The JSON response looks like this :

{
"o_gpid": 2000000237,
"o_bilreq": "BR-0000000371",
"o_netrv": "3603000000",
"o_ucogs": "3120900000",
"o_ntgp2": "482100000",
"o_prgp2": "13.3805162",
"o_ntfip": "303000000",
"o_ntgp3": "179100000",
"o_prgp3": "4.97085762",
"it_zgpbill": [
    {
        "gpid": 2000000237,
        "bilreq": "BR-0000000371",
        "posbr": 1,
        "vbeln": "3055",
        "posnr": 1,
        "matnr": "PC200-8M0/S1",
        "sernr": "SNOKT01",
        "netrv": "1201000000",
        "ucogs": "1040300000",
        "ntgp2": "160700000",
        "prgp2": "13.381",
        "ntfip": "101000000",
        "ntgp3": "59700000",
        "prgp3": "4.971"
    },
    {
        "gpid": 2000000237,
        "bilreq": "BR-0000000371",
        "posbr": 1,
        "vbeln": "3055",
        "posnr": 1,
        "matnr": "PC200-8M0/S1",
        "sernr": "SNOKT02",
        "netrv": "1201000000",
        "ucogs": "1040300000",
        "ntgp2": "160700000",
        "prgp2": "13.381",
        "ntfip": "101000000",
        "ntgp3": "59700000",
        "prgp3": "4.971"
    },
    {
        "gpid": 2000000237,
        "bilreq": "BR-0000000371",
        "posbr": 1,
        "vbeln": "3055",
        "posnr": 1,
        "matnr": "PC200-8M0/S1",
        "sernr": "SNOKT03",
        "netrv": "1201000000",
        "ucogs": "1040300000",
        "ntgp2": "160700000",
        "prgp2": "13.381",
        "ntfip": "101000000",
        "ntgp3": "59700000",
        "prgp3": "4.971"
    }
],
"it_zsfgp_pmp": [],
"it_zsfsapgp": [
    {
        "stat": "S",
        "msgnr": "000",
        "natxt": "Success"
    }
]

}

And from that JSON, I created class object like this :

Public class BRD_Recalculate_Response {
    Public String o_gpid;
    Public String o_bilreq;
    Public String o_netrv;
    Public String o_ucogs;
    Public String o_ntgp2;
    Public String o_prgp2;
    Public String o_ntfip;
    Public String o_ntgp3;
    Public String o_prgp3;
    Public List<it_zgpbill> it_zgpbill;
    Public List<it_zsfgp_pmp> it_zsfgp_pmp;
    Public List<it_zsfsapgp> it_zsfsapgp;
}

Public class it_zgpbill {
    Public String gpid;
    Public String bilreq;
    Public String posbr;
    Public String vbeln;
    Public String posnr;
    Public String matnr;
    Public String sernr;
    Public String netrv;
    Public String ucogs;
    Public String ntgp2;
    Public String prgp2;
    Public String ntfip;
    Public String ntgp3;
    Public String prgp3;
}

Public class it_zsfgp_pmp {

}

Public class it_zsfsapgp {
    Public String stat;
    Public String msgnr;
    Public String natxt;
}

But when I try to deserialize it using

List<BRD_Recalculate_Response> BRD_Recalculate_Response = (List<BRD_Recalculate_Response>)JSON.deserialize(responseString, List<BRD_Recalculate_Response>.class);

Im getting error :

Malformed JSON: Expected '[' at the beginning of List/Set

Answer 1

You are trying to serialize a single object json to List<SObject>. Convert your JSON back to its original form which is not List.Try below code. Hope this helps.

BRD_Recalculate_Response> BRD_Recalculate_Response = (BRD_Recalculate_Response)JSON.deserialize(responseString, BRD_Recalculate_Response.class);