Invalid parameter type in PostObject policy conditions

Problem

Your PostObject request to upload an object is rejected. The Post Policy form field contains a matching condition whose parameter does not match the expected data type for that condition operator.

Cause

A Post Policy defines the conditions that a PostObject request must satisfy. Each matching condition in the conditions array is itself an array whose elements must follow specific type rules. When a condition operator receives a parameter of the wrong type, the entire policy is considered invalid and the request fails.

Solution

The following policy corrects the parameter types for all condition operators.

{
    "expiration": "2023-02-19T13:19:00.000Z",
    "conditions": [    
        ["content-length-range", 1, 1024],
        ["eq", "$success_action_status", "201"],
        ["starts-with", "$key", "user/eric/"],
        ["in", "$content-type", ["image/jpeg", "image/png"]],
        ["not-in", "$cache-control", ["no-cache"]]
    ]
}

References

• For the complete Post Policy specification, see Appendix: Post Policy.

• For an example of uploading data to OSS from a web client by using form upload, see Add signatures on the client by using JavaScript and upload data to OSS.

• For common PostObject errors and troubleshooting methods, see PostObject errors and troubleshooting.