[SalesForce] deserializeStrict method: bug

The documentation about the deserializeStrict method in JSON class is (emphasis added):

All attributes in the JSON string must be present in the specified type. If the JSON content contains attributes not present in the System.Type argument, such as a missing field or object, deserialization fails in some circumstances. When deserializing JSON content with extraneous attributes into an Apex class, this method throws an exception in all API versions. However, no exception is thrown when you use this method to deserialize JSON content into a custom object or an sObject.

I wrote this code to test it:

String jsonString = '{"first":"value1", "second":"value2", "third":"value3"}';
Account c = (Account)JSON.deserializeStrict(jsonString, Account.class);
System.debug(c);`

And I receive this exception:

Exception: System.JSONException: No such column 'first' on sobject of type Account
StackTrace: Class.System.JSON.deserializeStrict: line 19, column 1
AnonymousBlock: line 2, column 1
AnonymousBlock: line 2, column 1
LINE: 19 COLUMN: 1

Reading the documentation I understand that no exception is thrown when you use this method to deserialize JSON content into a custom object or an sObject. Is this interpretation correct or not?

Best Answer

Aside from that last sentence the documentation is spot on. However, I would argue that the behavior is correct, and it is just that sentence which is flawed.

It is easy to demonstrate that for a custom object, it is flat out incorrect. What they mean is an instance of a custom defined class. Let's check:

Script

class Demo { }
Demo instance = (Demo)JSON.deserializeStrict('{"first": 1}', Demo.class);

Error

System.JSONException: Unknown field: Demo.first

Sure does throw.

It's a little trickier to demonstrate with an sObject, however. Sure, it throws an error with a concrete sObjectType, but it could in theory work for a generic instance.

Script

String payload = '{"first": 1}';
SObject record = (SObject)JSON.deserializeStrict(payload, SObject.class);

Error

System.JSONException: Nested object for polymorphic foreign key must have an attributes field before any other fields.

Okay...let's try adding that attribute:

Script

String payload = '{"attributes": {}, "first": 1}';
SObject record = (SObject)JSON.deserializeStrict(payload, SObject.class);

Error

System.JSONException:

Hmm...not that helpful. Let's try specifying a valid attributes value.

Script

String payload = '{"attributes":{"type":"Account"}, "first": 1}';
SObject record = (SObject)JSON.deserializeStrict(payload, SObject.class);

Error

System.JSONException: No such column 'first' on sobject of type Account

Back to the same error we had when it was a specific sObjectType.

Just to be sure, we can also try it with a custom sObjectType.

Script

MyObject__c record = (MyObject__c)JSON.deserializeStrict('{"first": 1}', MyObject__c.class);

Error

System.JSONException: No such column 'first' on sobject of type MyObject__c

So it looks like the documentation is in fact incorrect in that last sentence.

Related Solutions

[SalesForce] JSON.deserialize not ignoring unknown properties.

That statement apply for Apex type. You are expecting it to a custom object structure/column. During deserialization json try to assign values to product__c which is not a Apex class, it is a sobject so in that case json value try to find a exact match of column for product__c instance but it has different structure then json keys and throw error. I believe that json statement applies to primitives and objects only, not for sobject.

[SalesForce] JSON deserialize into wrapper class errors

Regarding the event_data issue: your JSON is inconsistent. In one case it's an object containing the user_agent string:

"event_data": {
                "user_agent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/45.0.2454.101 Safari/537.36"
            },

And elsewhere it's a list of quiz_data:

"event_data": [
                {
                    "quiz_question_id": "220",
                    "answer": null
                },
                {
                    "quiz_question_id": "221",
                    "answer": []
                } [...]
            ],

This wouldn't be picked up by a JSON linter, because it's just checking that the data is valid - not that it's consistent.

I notice that the parser code generated by JSON2Apex is different from your parser code above, and e.g. creates different classes to handle the different types of answers and event_data:

//
// Generated by JSON2Apex http://json2apex.herokuapp.com/
//

public class JSON2Apex {

    public class Answers {
        public String answer_exact;
        public String answer_error_margin;
        public String answer_range_start;
        public String answer_range_end;
        public String answer_weight;
        public String numerical_answer_type;
        public String blank_id;
        public String id;
        public String match_id;
        public String answer_text;
        public String answer_match_left;
        public String answer_match_right;
        public String answer_comment;
        public String answer_html;
        public String answer_match_left_html;
        public String answer_comment_html;
    }

    public class Quiz_data {
        public Integer id;
        public String regrade_option;
        public Integer points_possible;
        public String correct_comments;
        public String incorrect_comments;
        public String neutral_comments;
        public String correct_comments_html;
        public String incorrect_comments_html;
        public String neutral_comments_html;
        public String question_type;
        public String question_name;
        public String name;
        public String question_text;
        public List<Answers> answers;
        public String text_after_answers;
        public Integer assessment_question_id;
        public Integer position;
        public String published_at;
    }

    public class Answers_Z {
        public String id;
        public String text;
        public String comments;
        public String comments_html;
        public Integer weight;
        public String html;
    }

    public class Quiz_submission_events {
        public String id;
        public String event_type;
        public Event_data event_data;
        public String created_at;
    }

    public List<Quiz_submission_events> quiz_submission_events;

    public class Event_data {
        public Integer quiz_version;
        public List<Quiz_data> quiz_data;
    }

    public class Answers_Y {
        public Integer id;
        public String text;
        public String html;
        public String comments;
        public String comments_html;
        public Integer weight;
    }

    public class Answers_X {
    }

    public class Event_data_Z {
        public String user_agent;
    }

    public class Event_data_Y {
        public String quiz_question_id;
        public Object answer;
    }


    public static JSON2Apex parse(String json) {
        return (JSON2Apex) System.JSON.deserialize(json, JSON2Apex.class);
    }
}

This is an attempt to handle the inconsistencies in the JSON. I'm not sure whether it'll actually work in practice, but it's worth trying.

If it doesn't work, you have a few options.

Ideally you would change the JSON to be consistent, but that may not be an option if you're receiving it from a third party.
Alternatively, you could use JSON.deserializeUntyped() and check the type of each event_data at runtime, but you'd lose the advantages of typed deserialization.
Or, you could write custom parser code to manually check the value of event_data and parse it appropriately. If you check the Create explicit parse code box on JSON2Apex, you can take the parser code as a starting point.

Best Answer

Related Solutions

[SalesForce] JSON.deserialize not ignoring unknown properties.

[SalesForce] JSON deserialize into wrapper class errors

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