Hi Salesforce Gurus,

I am having issue with String length and need some input to proceed further.
I am building an API in which i will be receiving JSON request with some Keys and Values and a big encoded XML string. In my API, i am converting the BLOB request to tostring() for parsing the JSON request.
If the JSON request is less than 6000000 my API works fine. But if it more than 6000000 character i am getting the below error. 

[
  {
    "errorCode": "APEX_ERROR",
    "message": "System.StringException: String length exceeds maximum: 6000000
  }
]

Hi,

I need help in reading/storing and parsing big (~70-80 MB) XML file.

1] As per our requirement, the third party system will upload the xml on secure ftp, which we will need to bring in Salesforce.
I know Salesforce doesn't support FTP natively, I amy need to introduce a java/dotnet app in between or go for third party solutions like Jittebit or dataloader.io.

2] This xml will contain 2000-3000 records, each with approx 150 fields. We will need to prse this big xml, and upsert these records.
I have used Apex DOM to parse xmls in Salesforce, but not sure it will be the appropriate for our requirement.

​Any recommended appraoches for these requirements?

Thanks,