Download a file in a multipart response

This example demonstrates how to return a file in a form-data type HTTP multipart response while also transferring data of other types in the same message response.

Example multipart response

In this sample REST function there is an example of a multipart response. The RETURNS clause of the function has three return values: an INTEGER,STRING, and TEXT. The INTEGER is defined with the attribute WSHeader, so its value is sent in a HTTP header. The STRING and TEXT type have no WSHeader attributes, so therefore values are sent in the response body.

The TEXT return value is defined with the WSName attribute to identify it by the name "txt_file" instead of the DVM default name.
  • A variable (t) is defined as type TEXT and located in memory.
  • The readFile() method reads the contents of a text file ("README.txt") into variable t.
PUBLIC FUNCTION help2()
  ATTRIBUTES (WSGet,
              WSPath = "/help2")
  RETURNS (INTEGER ATTRIBUTE(WSHeader),
           STRING,
           TEXT ATTRIBUTE(WSName = "txt_file") )
    DEFINE t TEXT
    LOCATE t IN MEMORY
    CALL t.readFile("README.txt")
    RETURN 3, "hello world", t
END FUNCTION

Output of multipart HTTP response

In the output the header is given the default name, "rv0", at runtime.

In the multipart response parts are combined into one or more sets of data in the body. Parts are separated by boundaries, "--MIME_boundary" in the output example. The text file part is identified by the name ("txt_file")

Sample output of multipart HTTP response