Set resource path with WSParam and WSPath

Path parameters allow you to specify variables in the resource URL.

In the OpenAPI specification, path templates are the parts of the path that are replaceable with parameters. If you need to point to a specific resource within a collection (such as a user identified by ID) and when a pattern could match many similar resources, you use path templates in your REST function.

The OpenAPI specification denotes path templates within curly braces { }.
The path template {id} is substituted with actual values when a GWS client makes a call to the resource. In this example, the URI provides the user id "22":

You make a request to the resource with the URI. A function in your web service with the above path pattern processes the request.

The REST attributes WSPath and WSParam set in the attributes clause of the BDL function support path templating. WSPath may have many templates. For each input parameter with a WSParam attribute, there must be a matching template in the WSPath attribute value, otherwise compilation error-9111 is thrown.

Example: access a resource from path set with templates

In this sample function details of when a specified book was checked out by a library user are returned.

In the function's membersid parameter the attribute WSParam specifies the library member resource to return, and in its booksid parameter it specifies the book resource to return.

The path to the resource is set with two templates; {membersid} and {booksid}. These are set in the function attributes clause WSPath attribute:
ATTRIBUTES (WSGet,WSPath = "/members/{membersid}/books/{booksid}")
In an example endpoint URI to request the resoure, the value "48" representing the member id and the value "3" representing the book id, replace the variable parts of the path:

The function's output parameter bookList variable of type checkoutType returns the details.

WSThrows – is set to handle errors. In the TRY/CATCH block, the sqlca record is checked after the execution of the SQL query. The SQLERRMESSAGE is set to the message field of the userError variable, and a call to SetRestError() returns the message defined in WSThrows for the error.


TYPE checkoutType RECORD
           booksId INT,
           title VARCHAR(100),
           author VARCHAR(100),
           m_name VARCHAR(100),
           checkout_date DATETIME YEAR TO SECOND
        END RECORD

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

PUBLIC FUNCTION getBooksCheckedOut(membersid INTEGER ATTRIBUTE(WSParam),
  booksid INTEGER ATTRIBUTE(WSParam) )
              WSPath = "/members/{membersid}/books/{booksid}",
              WSDescription = "Get details when a library member checked out a specific book",
              WSThrows = "400:Invalid,406:@userError" )
    DYNAMIC ARRAY ATTRIBUTE(WSName = "Books_checked_Out") OF checkoutType )
    DEFINE bookList DYNAMIC ARRAY OF checkoutType
      DECLARE c1 CURSOR FOR SELECT b.booksid, b.title,,, c.checkoutdate
                              FROM books b
                              INNER JOIN checkouts c ON c.booksid = b.booksid
                              INNER JOIN members m ON m.membersid = c.membersid
                              WHERE c.booksid = booksid AND c.membersid = membersid

        FOREACH c1 INTO bookList[i].*
          LET i = i+1
        CALL bookList.deleteElement(bookList.getLength())
        # Remove the empty element implied by reference in FOREACH loop
       LET userError.message = SFMT("Error in SQL execution: %1 [%2]", 
                                     sqlca.sqlcode, SQLERRMESSAGE)
       CALL com.WebServiceEngine.SetRestError(406,userError)
    RETURN bookList

When to use WSParam or WSQuery

Know when to use WSParam or WSQuery attributes in your Web service.
  • Use a path parameter (with WSParam) to return a single entity given its id field.

    For example, /users/{id} specifies the entity in the resource path. If the entity specified by the {id} path parameter is not found, you typically get a "404 (Not found)" HTTP response code.

  • Use a query parameter (with WSQuery) for any field other than a resource id. A number of entities may be returned in the response.

    With a search or filter, you expect to return a number of entities in the response, unlike the single entity that you expect to get as the response for sending id as path parameter. WSQuery is the logical attribute to use for filtering, searching, or sorting resources.

    For example, in /users?lastname=smith, the search criteria is specified in a query parameter of the URL. If no entities are found matching the search or filter parameters, you typically get a "200 (OK)" HTTP response code with an empty array as the response body.