Stripping Nulls from a JSON object in Apex
NOTE: If you don’t’ want to read the wall of text/synopsis/description just scroll to the bottom. The function you need is there.
I feel dirty. This is the grossest hack I have had to write in a while, but it is also too useful not to share (I think). Salesforce did us an awesome favor by introducing the JSON.serialize utility, it can take any object and serialize it into JSON which is great! The only problem is that you have no control over the output JSON, the method takes no params except for the source object. Normally this wouldn’t be a big deal, I mean there isn’t a lot to customize about JSON usually, it just is what it is. There is however one case when you may want to control the output, and that is in the case of nulls. You see most of the time when you are sending JSON to a remote service, if you have a param specified as null, it will just skip over it as it should. Some of the stupider APIs try and process that null as if it were a value. This is especially annoying when the API has optional parameters and you are using a language like Apex which being strongly types makes it very difficult to modify an object during run time to remove a property. For example, say I am ordering a pizza, via some kind of awesome pizza ordering API. The API might take a size, some toppings, and a desired delivery time (for future deliveries). Their API documentation states that delivery time is an optional param, and if not specified it will be delivered as soon as possible, which is nice. So I write my little class in apex
And your resulting JSON looks like
Which in would work beautifully, unless the Pizza API is setup to treat any present key in the JSON object as an actual value, which in that case would be null. The API would freak out saying that null isn’t a valid datetime, and you are yelling at the screen trying to figure out why the stupid API can’t figure out that if an optional param has a null value, to just skip it instead of trying to evaluate it.
Now in this little example you could easily work around the issue by just specifying the prefferedDeliveryTime as the current date time if the user didn’t pass one in. Not a big deal. However, what if there was not a valid default value to use? In my recent problem there is an optional account number I can pass in to the API. If I pass it in, it uses that. If I don’t, it uses the account number setup in the system. So while I want to support the ability to pass in an account number, if the user doesn’t enter one my app will blow up because when the API encounters a null value for that optional param it explodes. I can’t not have a property for the account number because I might need it, but including it as a null (the user just wants to use the default, which Salesforce has no idea what is) makes the API fail. Ok, whew, so now hopefully we all understand the problem. Now what the hell do we do about it?
While trying to solve this, I explored a few different options. At first I thought of deserialize the JSON object back into a generic object (map<string,object>) and check for nulls in any of the key/value pairs, remove them then serialize the result. This failed due to difficulties with detecting the type of object the value was (tons of ‘unable to convert list<any> to map<string,object> errors that I wasn’t’ able to resolve). Of course you also have the recursion issue since you’ll need to look at every element in the entire object which could be infinity deep/complex so that adds another layer of complexity. Not impossible, but probably not super efficient and I couldn’t even get it to work. Best of luck if anyone else tries.
The next solution I investigated was trying to write my own custom JSON generator that would just not put nulls in the object in the first place. This too quickly fell apart, because I needed a generic function that could take string or object (not both, just a generic thing of some kind) and turn it into JSON, since this function would have to be used to strip nulls from about 15 different API calls. I didn’t look super hard at this because all the code I saw looked really messy and I just didn’t like it.
My solution that I finally decided to go for, while gross, dirty, hackish and probably earned me a spot in programmer hell is also simple and efficient. Once I remembered that JSON is just a string, and can be manipulated as such, I started thinking about maybe using regex (yes I am aware when you solve one problem with regex now you have two) to just strip out nulls. Of course then you have to worry about cleaning up syntax (extra commas, commas against braces, etc) when just just rip elements out of the JSON string, but I think I’ve got a little function here that will do the job, at least until salesforce offeres a ‘Don’t serialize nulls’ option in their JSON serializer.
Which after running on our previously generated JSON we get
Notice, no null prefferedDeliveryTime key. It’s not null, its just non existent. So there you have it, 6 lines of find and replace to remove nulls from your JSON object. Yes, you could combine them and probably make it a tad more efficient. I went for readability here. So sue me. Anyway, hope this helps someone out there, and if you end up using this, I’m sure I’ll see you in programmer hell at some point. Also, if anyone can make my initial idea of recursively spidering the JSON object and rebuilding it as a map of <string,object> without the nulls, I’d be most impressed.