This article has been depreciated, for current information on working with FME and REST, see the FME Server REST API Training course.

In the previous sections we have talked about REST and RPC and built a RPC web service. Now we will begin to create REST web services, by addressing a broader portion of the HTTP standard.

Defining the REST API

Let’s refer back to the our original definition of the functionality the web service should provide:

• Retrieve all of the parks in GeoJSON format.
• Retrieve a subset of the parks based on filter criteria.
• Add a completely new park.
• Update a park.
• Delete a park.

Now we will define the REST API based on these requirements.

HTTP Request-Method and URL

With REST, the HTTP Request-Method determines the action and the URL determines the resource to act on. So in a workspace we need to filter to an action using the Request-Method and extract the identifier out of the URL.

When a workspace is run on FME Server, the following parameters are provided with values:

• FME_SERVER_REQUEST_METHOD
• FME_SERVER_REQUEST_URI

As you might suspect, they provide the HTTP Request-Method and URL that were used in the web service call.

When you are authoring your workspace on FME Desktop, the parameters don’t have any values. So, for authoring purposes you should create two private parameters with the above names and set the values for testing.

Author the Workspace

• Open FME Workbench and continue with parks.fmw
• Select all of the existing transformers except the Creator, right click one of the transformers, select Create bookmark and name the bookmark: Get
• In the Navigator > Parameters > FME Server Parameters > double click FME_SERVER_REQUEST_METHOD
• Set the value to: GET
• In the Navigator > Parameters > FME Server Parameters > double click FME_SERVER_REQUEST_URI
  • Set the value to: https://<host>:<port>/fmedatastreaming/webservices/parks.fmw
  • Replace <host> with the actual hostname of your FME Server machine.
• After the Creator transformer add another ParameterFetcher and configure:
  • FME_SERVER_REQUEST_METHOD -> _FME_SERVER_REQUEST_METHOD
  • FME_SERVER_REQUEST_URI -> _FME_SERVER_REQUEST_URI
• Add an FMEServerURLSplitter transformer after the new ParameterFetcher.
  • Request URI: _FME_SERVER_REQUEST_URI
• Add a TestFilter transformer after the FMEServerURLSplitter.
  • If:
    fme_server_extra_url{0} attribute is missing AND _FME_SERVER_REQUEST_METHOD = GET
    then:
    Output Port: Get parks
• Connect the TestFilter's 'Get parks' port to the first ParameterFetcher. Ensure that the TestFilter’s ‘Get parks’ port is the only one that connects to the ParameterFetcher.
• Add a bookmark that contains the three transformers you just added and name it: Filter URL and HTTP Method
• Verify that the dogparks filter is still working correctly using Run > Prompt and Run
  
  

  Testing REST Web Services

  
  Pasting a URL into a web browser has the effect of sending an HTTP GET request with a query string to the web service. REST Web Services require also DELETE, PUT, POST methods, configuration of the Request-Body, and more. Most programming languages have these capabilities, but writing a problem is overkill if we just want to test the web service.
  
  Luckily there are quite a few clients for testing REST Web Services. Some browser based examples include REST Console, Postman, Advanced REST Client and HTTP Client. A popular command line tool cURL is a bit harder to use, but quite powerful. If you are using a Mac then HTTP Client works fine too. You will need to have one available for the remainder of the tutorial.

Downloads

Creating REST Web Services.zip