(SQL Server) curl with Variable Substitution in a GraphQL Request Body

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

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

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-- Important: See this note about string length limitations for strings returned by sp_OAMethod calls.
--
CREATE PROCEDURE ChilkatSample
AS
BEGIN
    DECLARE @hr int
    -- Important: Do not use nvarchar(max).  See the warning about using nvarchar(max).
    DECLARE @sTmp0 nvarchar(4000)
    DECLARE @success int
    SELECT @success = 0

    SELECT @success = 0

    -- Variable names are enclosed between {{ and }}
    -- Important: Variables should be placed inside the quotes.

    -- curl -X POST https://api.example.com/graphql \
    --   -H "Content-Type: application/graphql; charset=utf-8" \
    --   -H "Accept: application/json" \
    --   --data-binary "mutation {
    --   createUser(
    --     input: {
    --       name: \"{{name}}\"
    --       city: \"{{city}}\"
    --       note: \"{{note}}\"
    --       bio: \"{{bio}}\"
    --     }
    --   ) {
    --     id
    --     name
    --   }
    -- }"

    -- Build the above curl command.
    DECLARE @sbCurl int
    EXEC @hr = sp_OACreate 'Chilkat.StringBuilder', @sbCurl OUT
    IF @hr <> 0
    BEGIN
        PRINT 'Failed to create ActiveX component'
        RETURN
    END

    EXEC sp_OAMethod @sbCurl, 'AppendLn', @success OUT, 'curl -X POST https://api.example.com/graphql \'
    EXEC sp_OAMethod @sbCurl, 'AppendLn', @success OUT, '  -H "Content-Type: application/graphql; charset=utf-8" \'
    EXEC sp_OAMethod @sbCurl, 'AppendLn', @success OUT, '  -H "Accept: application/json" \'
    EXEC sp_OAMethod @sbCurl, 'AppendLn', @success OUT, '  -d "mutation {'
    EXEC sp_OAMethod @sbCurl, 'AppendLn', @success OUT, '  createUser('
    EXEC sp_OAMethod @sbCurl, 'AppendLn', @success OUT, '    input: {'
    EXEC sp_OAMethod @sbCurl, 'AppendLn', @success OUT, '      name: \"{{name}}\"'
    EXEC sp_OAMethod @sbCurl, 'AppendLn', @success OUT, '      city: \"{{city}}\"'
    EXEC sp_OAMethod @sbCurl, 'AppendLn', @success OUT, '      note: \"{{note}}\"'
    EXEC sp_OAMethod @sbCurl, 'AppendLn', @success OUT, '      bio: \"{{bio}}\"'
    EXEC sp_OAMethod @sbCurl, 'AppendLn', @success OUT, '    }'
    EXEC sp_OAMethod @sbCurl, 'AppendLn', @success OUT, '  ) {'
    EXEC sp_OAMethod @sbCurl, 'AppendLn', @success OUT, '    id'
    EXEC sp_OAMethod @sbCurl, 'AppendLn', @success OUT, '    name'
    EXEC sp_OAMethod @sbCurl, 'AppendLn', @success OUT, '  }'
    EXEC sp_OAMethod @sbCurl, 'AppendLn', @success OUT, '}"'

    DECLARE @curl int
    EXEC @hr = sp_OACreate 'Chilkat.HttpCurl', @curl OUT

    -- Provide values for variables
    EXEC sp_OAMethod @curl, 'SetVar', NULL, 'name', 'José O''Connor'
    EXEC sp_OAMethod @curl, 'SetVar', NULL, 'city', 'München'
    EXEC sp_OAMethod @curl, 'SetVar', NULL, 'note', 'He said "Hello, world!" — and left…'
    EXEC sp_OAMethod @curl, 'SetVar', NULL, 'bio', 'Loves sushi, café visits, and π ≈ 3.14159'

    -- 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.
    DECLARE @sbRawRequest int
    EXEC @hr = sp_OACreate 'Chilkat.StringBuilder', @sbRawRequest OUT

    EXEC sp_OAMethod @sbCurl, 'GetAsString', @sTmp0 OUT
    EXEC sp_OAMethod @curl, 'ToRawRequest', @success OUT, @sTmp0, @sbRawRequest
    IF @success = 0
      BEGIN
        EXEC sp_OAGetProperty @curl, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @sbCurl
        EXEC @hr = sp_OADestroy @curl
        EXEC @hr = sp_OADestroy @sbRawRequest
        RETURN
      END

    EXEC sp_OAMethod @sbRawRequest, 'GetAsString', @sTmp0 OUT
    PRINT @sTmp0

    -- The output is shown below.
    -- Notice the quote chars around "Hello, world!" are properly escaped.

    -- POST /graphql HTTP/1.1
    -- Accept: application/json
    -- Host: api.example.com
    -- Content-Type: application/graphql; charset=utf-8
    -- Content-Length: 250
    -- 
    -- mutation {
    --   createUser(
    --     input: {
    --       name: "José O'Connor"
    --       city: "München"
    --       note: "He said \"Hello, world!\" — and left…"
    --       bio: "Loves sushi, café visits, and π ≈ 3.14159"
    --     }
    --   ) {
    --     id
    --     name
    --   }
    -- }

    EXEC @hr = sp_OADestroy @sbCurl
    EXEC @hr = sp_OADestroy @curl
    EXEC @hr = sp_OADestroy @sbRawRequest


END
GO