Working with an old backend api that for some reason is adve

Question

Working with an old backend api that for some reason is advertised as taking json as input but it doesn t use ` ` it uses ` ` Is there an easy way to write an interceptor or something that just replace all double quotes with single quotes I m using okhttp + retrofit

Chris Lee · Answer

that s unfortunate don t know about the interceptor worth understanding how embedded single quotes within strings are represented so those don t get inadvertently replaced

Colton Idle · Answer

Asked my lead and he said that embedded single quotes just aren t supported sob

Chris Lee · Answer

scream

Chris Lee · Answer

gt advertised as taking json as input You already know this that isn t JSON Specs ```A string begins and ends with quotation marks ``` where quotation mark is 0x22 ` `

Chris Lee · Answer

if there s no chance of a single quote showing up inside a string is it possible to do a global replace ` ` gt ` ` when generating the json or is that generation buried in the framework

Colton Idle · Answer

Yeah Best part is if I hand it valid json I get a raw response of ``` Input is not valid json ``` which is funny because even the response isn t proper json because it doesn t have lol

ephemient · Answer

I believe the <https github com stleary JSON java|https github com stleary JSON java> is lenient enough to parse single quoted strings it s a pretty ludicrous solution but you could parse and re stringify with it

ephemient · Answer

oh wait you need to produce invalid JSON wtf

Chris Lee · Answer

Looks like Jackson may have some <https github com FasterXML jackson core issues 549|support> for this

eygraber · Answer

Is your backend using python

yschimke · Answer

I think that s still valid

yschimke · Answer

gt Early versions of JSON such as specified by RFC 4627 required that a valid JSON text must consist of only an object or an array type which could contain other types within them This restriction was dropped in RFC 7158 where a JSON text was redefined as any serialized value

Chris Lee · Answer

even RFC 4627 specifies quotation marks ` `

yschimke · Answer

Sorry was trying to reply to the error message not being valid JSON

Chris Lee · Answer

ah yea that

Chris Lee · Answer

it s likely the back end here is taking a shortcut calling it json but not directly parsing it instead dropping it to language specific object representation Python or JS

Chris Lee · Answer

which means it s potentially vulnerable to all kinds of injection attacks face with rolling eyes

eygraber · Answer

Yeah I used to get back True and False from an API The backend engineers were just dumping python objects ツ

Chris Lee · Answer

engineers see no evil

Colton Idle · Answer

So it seems like moving to jackson is the current front runner as an option to produce invalid json to send to the server

ephemient · Answer

well it wouldn t be too hard to write a transformer from ` ` based JSON to ` ` based

Chris Lee · Answer

what are you using now does it have a similar option to use single quotes If not then you have options for Jackson or a search replace

Colton Idle · Answer

transformer do you mean interceptor Or is transformer something I just don t know about smile

Colton Idle · Answer

I m using moshi now Let me look at it s docs issue page

ephemient · Answer

well I mean like a simple state machine can handle it and sure you could put that in an interceptor

ephemient · Answer

```private enum class State Outside InsideString BeginEscape fun jsonHack json String String = buildString json length var state = State Outside for c in json when state State Outside gt when c gt append state = State InsideString else gt append c State InsideString gt when c gt append state = State Outside gt append c state = State BeginEscape gt append else gt append c State BeginEscape gt append c state = State InsideString check state == State Outside ```

Colton Idle · Answer

Gotcha Didn t know if an interceptor would essentially just let me do a replace I ll give this a shot when I m back at my desk

Chris Lee · Answer

depends on what altitude the interceptor is at the above will work if you can intercept the generated json it s perhaps possible to intercept during generation over riding encoding of a string for example

ephemient · Answer

well you get a Sink in ResponseBody so you can either stringify the whole thing or change the above to wrap it in a FilteringSink or something as long as it s UTF 8 or similar it ll work fine on bytes

ephemient · Answer

oh I guess there s a FilterOutputStream but there isn t a FilterSink well a custom ForwardingSink or something like that then

yschimke · Answer

yschimke · Answer

ForwardingResponseBody is a test only class but ForwardingSource is public API of okio

ephemient · Answer

well it s a little different on the request side but if you don t mind the extra conversions it s easy to ```object JsonHack Interceptor override fun intercept chain Interceptor Chain Response val request = chain request return chain proceed request newBuilder method request method request body let body gt val buffer = Buffer body writeTo buffer buffer readUtf8 jsonHack toRequestBody body contentType build ``` using the previous function

yschimke · Answer

There also a request example <https github com square okhttp blob 248b0e6318f4ff7ce378b0ee29e4bc9993f992e3 okhttp testing support src main kotlin okhttp3 UppercaseRequestInterceptor kt|https github com square okhttp blob 248b0e6318f4ff7ce378b0ee29e4bc9993f992e3 okh support src main kotlin okhttp3 UppercaseRequestInterceptor kt>

jessewilson · Answer

Just enable lenient parsing in your Json thingy <https square github io moshi 1 x moshi com squareup moshi JsonReader html setLenient boolean >

jessewilson · Answer

```val lenientJsonAdapter = strictJsonAdapter lenient ```

Chris Lee · Answer

it s the outgoing json the consumer of that json that expects malformed json and is purportedly not able to change

jessewilson · Answer

In that case I recommend getting the author of that endpoint fired and replaced with somebody else