(Lianja) 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.

Note: This example requires Chilkat v11.5.0 or greater.

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llSuccess = .F.

// 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}}}'

loSbCurl = createobject("CkStringBuilder")
loSbCurl.AppendLn('curl -X POST https://api.example.com/messages \")
loSbCurl.AppendLn('  -H "Content-Type: application/json" \")
loSbCurl.AppendLn('  -d '{"text":"{{message}}"}'')

loCurl = createobject("CkHttpCurl")

// In this example, the value we'll provide for the "message" variable
// will contain chars that require JSON escaping.
loCurl.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.
loSbRawRequest = createobject("CkStringBuilder")
llSuccess = loCurl.ToRawRequest(loSbCurl.GetAsString(),loSbRawRequest)
if (llSuccess = .F.) then
    ? loCurl.LastErrorText
    release loSbCurl
    release loCurl
    release loSbRawRequest
    return
endif

? loSbRawRequest.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!\""}


release loSbCurl
release loCurl
release loSbRawRequest