PowerBuilder

curl with Variable Substitution in a JSON Request Body

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This example shows how to use variables inside a JSON request body using the {{variable_name}} syntax. When the HTTP request’s Content-Type indicates JSON, Chilkat automatically applies proper JSON escaping to each substituted value, ensuring the resulting JSON remains valid. PowerBuilder

integer li_rc
integer li_Success
oleobject loo_SbCurl
oleobject loo_Curl
oleobject loo_SbRawRequest

li_Success = 0

// Variable names are enclosed between {{ and }}
// Important: The variable {{var_name}} should be placed inside the quotes.

// This is correct:
// curl -X POST https://api.example.com/messages \
//   -H "Content-Type: application/json" \
//   -d '{"text":"{{message}}"}'

// This is incorrect:
//   -d '{"text":{{message}}}'

loo_SbCurl = create oleobject
li_rc = loo_SbCurl.ConnectToNewObject("Chilkat.StringBuilder")
if li_rc < 0 then
    destroy loo_SbCurl
    MessageBox("Error","Connecting to COM object failed")
    return
end if
loo_SbCurl.AppendLn("curl -X POST https://api.example.com/messages ~")
loo_SbCurl.AppendLn("  -H ~"Content-Type: application/json~" ~")
loo_SbCurl.AppendLn("  -d '{~"text~":~"{{message}}~"}'")

loo_Curl = create oleobject
li_rc = loo_Curl.ConnectToNewObject("Chilkat.HttpCurl")

// In this example, the value we'll provide for the "message" variable
// will contain chars that require JSON escaping.
loo_Curl.SetVar("message","He said ~"Hello, world!~"")

// To demonstrate how the variables are replaced, this example does not execute the curl command. 
// Instead, it generates the raw HTTP request that would be sent if the curl command were run.
loo_SbRawRequest = create oleobject
li_rc = loo_SbRawRequest.ConnectToNewObject("Chilkat.StringBuilder")

li_Success = loo_Curl.ToRawRequest(loo_SbCurl.GetAsString(),loo_SbRawRequest)
if li_Success = 0 then
    Write-Debug loo_Curl.LastErrorText
    destroy loo_SbCurl
    destroy loo_Curl
    destroy loo_SbRawRequest
    return
end if

Write-Debug loo_SbRawRequest.GetAsString()

// The output is shown below.
// Notice that the quote chars around "Hello World!" are properly JSON escaped.

// POST /messages HTTP/1.1
// Host: api.example.com
// Content-Type: application/json
// Content-Length: 36
// 
// {"text":"He said \"Hello, world!\""}


destroy loo_SbCurl
destroy loo_Curl
destroy loo_SbRawRequest