com.WebServiceEngine.SetRestError

Manages error handling for a REST high-level Web Service function.

Syntax

com.WebServiceEngine.SetRestError(
   code INTEGER
   error any-type )
  1. code defines a standard HTTP response status code (400 - 599) as defined in RFC 2616 Section 10.4 and RFC 2616 Section 10.5
  2. error defines the program variable that has details of the error. The any-type can be any Genero BDL variable type: RECORD, ARRAY, or simple data type. It can return a NULL value.

Usage

You use this method to set the HTTP status code and details of the error to be returned to the client when the request to the resource has finished. SetRestError accepts the HTTP code, a Genero BDL variable (if any), or a text description to be returned. This method must be called inside a Web Service REST high-level function.

If the SetRestError() method error parameter references a variable, the variable must be specified in the WSThrows declaration of the function, otherwise the method fails and returns an error code of -15570.

Variables referenced by WSThrows, must be defined as PUBLIC at the modular level and specified with the WSError attribute.

If WSThrows does not reference a variable, just a message string (for example "404:my error message"), you must call the method with the NULL value (SetRestError(404,NULL)) to send the "my error message" as the HTTP reason phrase. Ultimately, this will depend on whether the web server allows you to change the standard protocol message or not.

It is recommended that if you need to ensure an error description other than the standard protocol message is returned to the client, you must use WSThrows with "code:@variable" option and call the method with a reference to the variable, for example SetRestError(400,myError).

In the examples Example 1: managing expected errors and Example 2: managing unexpected errors different uses of the method are shown.

Example 1: managing expected errors

In this example, common application level type errors, like resource not found, are expected. Instead of the standard HTTP status code (400 bad request), the call to SetRestError(400,myerror) will send the description set on the myError.message variable as the reason for the error. 

PUBLIC DEFINE myError RECORD ATTRIBUTE(WSError="user error")
  message STRING
END RECORD

PUBLIC
FUNCTION queryAccountById(id VARCHAR(10) ATTRIBUTE(WSParam)
    )
    ATTRIBUTES(WSGet,
        WSPath="/accounts/{id}",
        WSThrows="400:@myError,500:Internal Server Error")
    RETURNS accountType ATTRIBUTES(WSName="body")

  DEFINE thisAccount RECORD LIKE accounts.*
  # ... retrieve user id from database ...

    CASE sqlca.sqlcode
    WHEN 0
        EXIT CASE
    WHEN NOTFOUND
        LET myError.message = SFMT("Could not find account id :%1",id)
        CALL com.WebServiceEngine.SetRestError(400,myError)
    OTHERWISE
        CALL com.WebServiceEngine.SetRestError(500,NULL)
    END CASE
    RETURN thisAccount.*
END FUNCTION

Example 2: managing unexpected errors

Tip:

In general, the recommended option is to list all the expected errors as shown in Example 1, in order to get them generated in the OpenAPI specification file and trapped on the client side.

In this example you code to trap a status code not defined in the WSThrows list. In the call to the SetRestError() method the status code and optionally the error variable is returned. 

PUBLIC DEFINE myError RECORD ATTRIBUTE(WSError="user error")
  message STRING
END RECORD

PUBLIC
FUNCTION queryAccountById(id VARCHAR(10) ATTRIBUTE(WSParam)
    )
    ATTRIBUTES(WSGet,
        WSPath="/accounts/{id}",
        WSThrows="400:@myError,500:Internal Server Error")
    RETURNS accountType ATTRIBUTES(WSName="body")
  
  DEFINE thisAccount RECORD LIKE accounts.*
  # ... retrieve user id from database ...

    CASE sqlca.sqlcode
    WHEN 0 # success
        EXIT CASE
    WHEN NOTFOUND
        LET myError.message = SFMT("Could not find account id :%1",id)
        CALL com.WebServiceEngine.SetRestError(400,myError)
    WHEN < 0 
        CALL com.WebServiceEngine.SetRestError(500,NULL)
    OTHERWISE
       CALL com.WebServiceEngine.SetRestError(505,NULL)
    END CASE
    RETURN thisAccount.*
END FUNCTION