WSHeader

Defines custom headers in the request and response of Web service functions.

Syntax

WSHeader

Where:

WSHeader in an ATTRIBUTES() clause of an input parameter or return value of the function defines a HTTP header.

WSHeader is an optional attribute.

Usage

Use the WSHeader attribute to define a custom header in an input parameter or in a return value. Custom headers are commonly used to provide information; however, you can also use them to pass data that implements logic on the server or client side.

Typically, you use WSHeader to pass data related to the service in the form of an HTTP header. For example, an input parameter defined with ATTRIBUTES(WSHeader, WSName="Authorization") sets the standard HTTP authorization header.

You can set the WSHeader attribute on parameters defined as primitive types, records, arrays, and simple dictionary type.

WSHeader supports the OpenAPI default styles: style: simple and explode: false. Table 1 shows how the header (X-MyHeader) is serialized when the parameter (id) is a primitive type, an array, record, and a dictionary type. The dictionary and record types are defined as objects according to the OpenAPI specification. For further information on OpenAPI serialization, see the Parameter serialization page.
Table 1. OpenAPI header parameters and serialization
style explode URI template Primitive value X-MyHeader = 5 Array X-MyHeader = [3, 4, 5] Object X-MyHeader = {"role": "admin", "firstName": "Alex"}
simple false {id} X-MyHeader:5 X-MyHeader: 3,4,5 X-MyHeader: role,admin,firstName,Alex
The GWS and fglrestful supports serialization and deserialization of parameters according to defaults set by the OpenAPI specification. If a value contains special characters as defined by RFC3986 (for example, :/?#[]@!$&'()*+,;=), the GWS engine serializes them with percent-encoding in the parameter. For example:
DEFINE b DYNAMIC ARRAY OF STRING = ["O,ne", "Two", "Three", NULL, "Five"]
The parameter contains: O%2Cne,Two,Three,,Five. The server and the client must deserialize "O%2Cne" to "O,ne" for insertion in Genero BDL.

Use WSName with WSHeader to name headers; otherwise the GWS gives the headers default names ("rv0", "rv1", etc) at runtime.

Example: WSHeader and WSName in input parameter

In the sample REST function, the Genero Application Server (GAS) environment variable "X-FourJs-Environment-Variable-REMOTE_ADDR" that contains the IP address of the remote client is passed in a header.

As the GAS variable has hyphens ("-"), which are not allowed in Genero BDL variables, the WSName attribute is set on the ip_addr parameter to identify "X-FourJs-Environment-Variable-REMOTE_ADDR" in the HTTP request.

The ip_addr parameter is BDL friendly and this is used in the function. The parameter is also optional as defined by the attribute WSOptional.
Tip:

The WSContext attribute, if set, can provide your service with access to environment variables set by the GAS. 

PUBLIC FUNCTION getRemoteAddress (ip_addr STRING
   ATTRIBUTES(WSHeader, 
              WSOptional, 
              WSName = "X-FourJs-Environment-Variable-REMOTE_ADDR") )
   ATTRIBUTES (WSGet, 
               WSPath = "/users/ip",
               WSDescription = "Get remote address of the client")
   RETURNS (INTEGER ATTRIBUTES(WSHeader), STRING)
   DEFINE ip STRING
     LET ip = ip_addr
     IF ip IS NULL THEN
        LET ip = "Got no remote address."
     ELSE
        LET ip = SFMT("Hello there, you're at %1",ip )
     END if
     RETURN 3, ip
END FUNCTION

Example responses in header and body

In this sample REST function data is returned in a header and in the message body. The function's RETURNS clause has two return values:
  • An integer is returned in a header. It is specified with the WSHeader attribute.
  • A string is returned in the body. It is specified without an attribute.
PUBLIC FUNCTION help()
  ATTRIBUTES (WSGet,
              WSPath = "/help")
  RETURNS (INTEGER ATTRIBUTE(WSHeader, WSDescription = "Reference number"),
    STRING)
    RETURN 3, "Hello world"
END FUNCTION
Figure: Output of the HTTP response

Sample output of the HTTP response
In the output the header is given a default name, "rv0", at runtime. You can change default header naming via the WSName attribute.
Warning: Standard response headers

Setting a standard HTTP header on a response must be handled with care, especially for those that define the response body such as Content-Type, or Content-Encoding. Make sure what you define with WSName does not conflict with what is specified in the OpenAPI documentation for the service.

Example: WSHeader returns a record

In this sample REST function data is sent in a custom header in the RETURNS clause of the function on a user-defined record type ("T_RECORD"). The string ("Return record in header: ..." ) is returned in the response body. 
PUBLIC TYPE t_user RECORD
         user_id INTEGER,
         user_name VARCHAR(50)
     END RECORD

PUBLIC FUNCTION getUserInfo(
    p_user_id INTEGER ATTRIBUTES(WSHeader, WSOptional))
    ATTRIBUTES(WSGet,
        WSPath = "/v1/ok",
        WSDescription = "Return user record in header",
        WSRetCode = "202:Accepted",
        WSThrows = "400:Bad Request,401:Unauthorized,500:Internal Server Error")
    RETURNS(STRING ATTRIBUTES(WSMedia = "application/json"),
        t_user ATTRIBUTES(WSHeader))

    DEFINE u t_user

    SELECT * INTO u.* FROM user WHERE user_id = p_user_id

    RETURN "User info is in header...", u

END FUNCTION

Example: WSHeader returns data in a dictionary

In this sample REST function a list of available bikes is returned in a DICTIONARY OF STRING set in the custom header dict.

The function's input parameter thisBike passes a value representing a model of bike in a header. The WSGet attribute is set to request details about thisBike from the service. The dictionary dict is queried for details of thisBike.

WSThrows is set to handle errors. The message field of the userError variable is set if the bike is not found, and a call to SetRestError() returns the message defined in WSThrows for the error.

IMPORT com

PUBLIC DEFINE userError RECORD ATTRIBUTE(WSError = "User error")
  message STRING
END RECORD

PUBLIC FUNCTION getBikeDetails(
    thisBike STRING ATTRIBUTES(WSHeader))
    ATTRIBUTES(WSGet,
        WSPath = "/bikes",
        WSDescription = "Get bike details. Return list of available bikes",
        WSRetCode = "202:Accepted",
        WSThrows = "404:@userError")
    RETURNS(STRING ATTRIBUTES(WSMedia = "application/xml, application/json"),
        DICTIONARY ATTRIBUTES(WSHeader, WSName = "dict") OF STRING)

    DEFINE b STRING
    DEFINE dict DICTIONARY OF STRING
    DEFINE keys DYNAMIC ARRAY OF STRING
    DEFINE i INT

    LET dict["YZF"] = "250cc"
    LET dict["Z650"] = "652cc"
    LET dict["MT-07"] = "689cc"
    
    LET b = "Bike details"
    LET keys = dict.getKeys()
    DISPLAY "Number bikes: ", dict.getLength()
    FOR i = 1 TO keys.getLength()
        DISPLAY i, " ", keys[i], " ", dict[keys[i]]
    END FOR

    IF dict.contains(thisBike) THEN
        LET b = SFMT("This bike has: %1 ", dict[thisBike])
    ELSE
        LET userError.message = SFMT("Could not find '%1' ", thisBike)
        CALL com.WebServiceEngine.SetRestError(404, userError)
    END IF
    RETURN b, dict

END FUNCTION