Import REST API in Tableau – Read JSON, SOAP XML, CSV

Now let's look at how to configure ZappySys Data Gateway. This feature acts as a bridge between Client App and ZappySys Drivers. Using data gateway you can use ZappySys Drivers inside applications / operating systems where ZappySys drivers may not be available directly for some reason (e.g. You don't have access to Server for Installation or System does not support ODBC drivers like JAVA programs). Click here to read more on various use cases of Data Gateway.

Configure Data Gateway User / Port

Now let's look at steps to configure Data Gateway after installation. We will also create a sample data source for ODATA API (i.e. JSON based REST API Service).

1. Assuming you have installed ZappySys ODBC PowerPack using default options (Which also enables Data Gateway Service)
2. Search "Gateway" in your start menu and click ZappySys Data Gateway
   

   Open ZappySys Data Gateway

3. First make sure Gateway Service is running (Verify Start icon is disabled)
4. Also verify Port on General Tab
   

   Port Number setting on ZappySys Data Gateway

5. Now go to Users tab. Click Add icon to add a new user. Check Is admin to give access to all data sources you add in future. If you don't check admin then you have to manually configure user permission for each data source.
   

   Add Data Gateway User

 

Configure Data Source

1. After user is added, go to Data Sources tab. Click Add icon to create new data source. Select appropriate driver based on your API / File format. You can choose Generic ODBC option to read data from ODBC DSN or use Native Driver option.

   NOTE: Whenever possible use native driver option for better performance / security and ease of use.

   

   Add Gateway Data Source (Native JSON Driver)

2. Click on "Edit" under Data source and configure as per your need (e.g. Url, Connection, Request Method, Content Type, Body, Pagination etc.). For this demo we are going to pick simple JSON REST API which doesn't need any authentication.  Enter following URL.

   https://services.odata.org/V3/Northwind/Northwind.svc/Invoices?$format=json

3. You can also view response structure and select default hierarchy (i.e. Filter) like below (Select Array Icon) for data extraction.
   

   Configure JSON API Data source

Test SQL Query / Preview Data

1. Now go to Preview Tab. You can click Preview button to execute default query OR Select Table name from dropdown to generate SQL with column names.
   

   JSON / REST API Driver Query Preview / Query Examples (Read REST API or JSON Files)

2. You can also click Query Builder to generate SQL using different options in WITH clause. ANy setting you specify in WITH clause will override UI settings we applied in previous steps.
   

   Using SQL Query Builder (For Files or REST / SOAP API - JSON / XML / CSV Format)

3. There is another useful option for code generation. Select your Language and quickly copy code snippet. See below Example of XML Driver Query to call SOAP API.
   

   Generate Example Code for ZappySys Driver

4. Click OK to Close Data Source UI
5. Once data source is tested and configured you can click Save button in the Gateway UI toolbar and click Yes for Restart Service.

 

Once you configured data source in Gateway, we can now setup Linked Server in SQL Server to query API data.

1. Assuming you have installed SQL Server and SSMS. If not then get both for FREE from here: Get SQL Server Express and  Get SSMS
2. Open SSMS and connect to SQL Server.
3. Go to Root > Server Objects > Linked Servers node. Right click and click New Linked Server...
   

   Add Linked Server in SQL Server

4.  Now enter linked server name, select Provider as SQL Native Client
5. Enter data source as GatewayServerName,PORT_NUMBER where server name is where ZappySys Gateway is running (Can be same as SQL Server machine or remote machine). Default PORT_NUMBER is 5000 but confirm on Data gateway > General tab incase its different.
6. Enter Catalog Name. This must match name from Data gateway Data sources grid > Name column
   

   Configure Linked Server Provider, Catalog, Server, Port for ZappySys Data Gateway Connection

7. Click on Security Tab and select last option "Be made using this security context". Enter your gateway user account here.

8. Optional: Under the Server Options Tab, Enable RPC and RPC Out and Disable Promotion of Distributed Transactions(MSDTC).

   

   RPC and MSDTC Settings

   ---

   You need to enable RPC Out if you plan to use EXEC(...) AT [MY_LINKED_SERVER_NAME] rather than OPENQUERY.
   If don't enabled it, you will encounter the 'Server "MY_LINKED_SERVER_NAME" is not configured for RPC' error.

   Query Example: EXEC('Select * from Products') AT [MY_LINKED_SERVER_NAME]

   ---

   If you plan to use 'INSERT INTO...EXEC(....) AT [MY_LINKED_SERVER_NAME]' in that case you need to Disable Promotion of Distributed Transactions(MSDTC).
   If don't disabled it, you will encounter the 'The operation could not be performed because OLE DB provider "SQLNCLI11" for linked server "MY_LINKED_SERVER_NAME" was unable to begin a distributed transaction.' error.

   Query Example:

   Insert Into dbo.Products 
   EXEC('Select * from Products') AT [MY_LINKED_SERVER_NAME]

   ---

9. Click OK to save Linked Server
10. In SSMS execute below SQL query to test your connectivity.

    SELECT * FROM OPENQUERY( MY_LINKED_SERVER_NAME, 'SELECT * FROM $')

    --OR--

    SELECT * FROM OPENQUERY( MY_LINKED_SERVER_NAME, 
    'SELECT * FROM $
     WITH (Src=''https://services.odata.org/V3/Northwind/Northwind.svc/Customers?$format=json''
     ,Filter=''$.value[*]''
     ,DataFormat=''OData''
    )');

11. Here is the preview after you run some REST API query in SQL Server. Notice that you can override default configuration by supplying many parameters in WITH clause (second query example in screenshot).
    

    SSMS Output - Query REST API via Linked Server OPENQUERY statement (Connect to ZappySys Data Gateway)

12. You can wrap your queries inside View or wrap inside Stored procedure to parameterize. Here is an example of create view which calls REST API queries. Below View can be consumed like a normal table from any Tools or Programming Language which supports connectivity to SQL Server.

    CREATE VIEW dbo.vwApiInvoices 
    AS 
    /*Call REST API inside SQL Server View*/
    SELECT * FROM OPENQUERY( LS , 
    'SELECT * FROM $
    WITH (Src=''https://services.odata.org/V3/Northwind/Northwind.svc/Invoices?$format=json''
    	 ,Filter=''$.value[*]''
    	 ,DataFormat=''OData''
    )');
    
    GO
    

     
13. Notice in above approach if you parameterize Stored Procedure then check this article to understand Dynamic Metadata.
14. That's it. We are now ready to move forward with more interesting things in next section.

Paginate by Response Attribute

This example shows how to paginate API calls where you need to paginate until the last page detected. In this example, next page is indicated by some attribute called nextlink (found in response). If this attribute is missing or null then it stops fetching the next page.

SELECT * FROM $
WITH(
SRC=@'https://zappysys.com/downloads/files/test/pagination_nextlink_inarray_1.json'
,NextUrlAttributeOrExpr = '$.nextlink'  --keep reading until this attribute is missing. If attribute name contains dot then use brackets like this $.['my.attr.name']
)

Paginate by URL Parameter (Loop until certain StatusCode)

This example shows how to paginate API calls where you need to pass page number via URL. The driver keeps incrementing page number and calls next URL until the last page detected (401 error). There are few ways to indicate the last page (e.g. By status code, By row count, By response size). If you don't specify end detection then it will use the default (i.e. No records found).

SELECT * FROM $
WITH (
SRC=@'https://zappysys.com/downloads/files/test/page-xml.aspx?page=1&mode=DetectBasedOnResponseStatusCode'
,PagingMode='ByUrlParameter'
,PagingByUrlAttributeName='page'
,PagingByUrlEndStrategy='DetectBasedOnResponseStatusCode'
,PagingByUrlCheckResponseStatusCode=401
,IncrementBy=1
)

Paginate by URL Path (Loop until no record)

This example shows how to paginate API calls where you need to pass page number via URL Path. The driver keeps incrementing page number and calls next URL until the last page is detected. There are few ways to indicate the last page (e.g. By status code, By row count, By response size). If you don't specify end detection then it will use the default (i.e. No records found).

SELECT * FROM $
WITH (
SRC=@'https://zappysys.com/downloads/files/test/cust-<%page%>.xml'
,PagingMode='ByUrlPath'
,PagingByUrlAttributeName='<%page%>'
,PagingByUrlEndStrategy='DetectBasedOnRecordCount'
,IncrementBy=1
)

Paginate by Header Link (RFC 5988)

API like GitHub / Wordpress use Next link in Headers (RFC 5988)

SELECT * FROM $
LIMIT 25
WITH(
	 Src='https://wordpress.org/news/wp-json/wp/v2/categories?per_page=10'
	,PagingMode='ByResponseHeaderRfc5988'
	,WaitTimeMs='200' --//wait 200 ms after each request
)

 

• HTTP
• OAuth

HTTP Connection

• SOAP WSS (when accessing a SOAP WebService)
• Static Token / API Key (when need to pass an API key in HTTP header)
• Dynamic Token (same as Static Token method except that each time you need to log in and retrieve a fresh API key)
• JWT Token (As per RFC 7519)

OAuth

If you are trying to access REST API resource, it is a huge chance, you will need to use OAuth Connection. Read this article to understand how OAuth authentication and authorization works and how to use it (article originally was written for SSIS PowerPack, but the concepts and UI stay the same): https://zappysys.com/blog/rest-api-authentication-with-oauth-2-0-using-ssis

There are few settings you can coder while calling Web API

API Limit / Throttling

While calling public API or other external web services one important aspect you have to check,  how many requests are allowed by your API. Especially when you use API pagination options to pull many records you have to slow down based on API limits. For example, your API may allow you only 5 requests per second. Use Throttling Tab on Driver UI to set delay after each request.

2D Array Transformation

If you are using JSON or XML API Driver then possible you may have to transform your data using 2D array transformation feature. Check this link for more information.  

While calling APIs you may face some performance issues. There are a few tips you can consider to speed up things.

Use Server-side filtering if possible in URL or Body Parameters

Many API supports filtering your data by URL parameters or via Body. Whenever possible try to use such features.  Here is an example of odata API, In the below query the first query is faster than the second query because in the first query we filter at the server.

SELECT * FROM value
WITH(
	 Src='https://services.odata.org/V3/Northwind/Northwind.svc/Customers?$format=json&$filter=Country eq ''USA'''
	,DataFormat='Odata'
)

-- Slow query - Client-side filtering
SELECT * FROM value
WHERE Country ='USA'
WITH(
	 Src='https://services.odata.org/V3/Northwind/Northwind.svc/Customers?$format=json'
	,DataFormat='Odata'
)

Avoid Special features in SQL Query (e.g. WHERE, Group By, Order By)

ZappySys API engine triggers client-side processing if special features are used in Query. Following SQL Features will trigger Client-Side processing which is several times slower than server-side processing. So always try to use simple query (Select col1, col2 .... from mytable )

• WHERE Clause
• GROUP BY Clause
• HAVING Clause
• ORDER BY
• FUNCTIONS (e.g. Math, String, DateTime, Regex... )

LIMIT clause does not trigger client-side processing.

Consider using pre-generated Metadata / Cache File

Use META option in WITH Clause to use static metadata (Pre-Generated)There are two more options to speedup query processing time. Check this article for details.

1. select * from value WITH( meta='c:\temp\meta.txt' )
   --OR--
   select * from value WITH( meta='my-meta-name' )
   --OR--
   select * from value WITH( meta='[ {"Name": "col1", "Type": "String", Length: 100}, {"Name": "col2", "Type": "Int32"} ...... ]' )

2. Enable Data Caching Options (Found on Property Grid > Advanced Mode Only )

Consider using Metadata / Data Caching Option

ZappySys API drivers support Caching Metadata and Data rows to speed up query processing. If your data doesn't change often then you can enable this option to speed up processing significantly. Check this article for details how to enable Data cache / metadata cache feature for datasource level or query level. To define cache option at query level you can use like below.

SELECT * FROM $
WITH 
(  SRC='https://myhost.com/some-api'
  ,CachingMode='All'  --cache metadata and data rows both
  ,CacheStorage='File' --or Memory
  ,CacheFileLocation='c:\temp\myquery.cache'
  ,CacheEntryTtl=300 --cache for 300 seconds
)

   

Use --FAST Option to enable Stream Mode

ZappySys JSON / XML drivers support --FAST suffix for Filter. By using this suffix after Filter driver enables Stream Mode, Read this article to understand how this works.

SELECT * FROM $ 
LIMIT 10 --//add this just to test how fast you can get 10 rows
WITH(
  Filter='$.LargeArray[*]--FAST' --//Adding --FAST option turn on STREAM mode (large files)
 ,SRC='https://zappysys.com/downloads/files/test/large_file_100k_largearray_prop.json.gz'
 --,SRC='c:\data\large_file.json.gz'
 ,IncludeParentColumns='False'  --//This Must be OFF for STREAM mode (read very large files)
 ,FileCompressionType='GZip' --Zip or None (Zip format only available for Local files)
)

 

To call SOAP API you need to know Request XML Body Structure. If you are not sure how to create SOAP Request body then no worries. Check this article to learn how to generate SOAP Request body using the Free tool SoapUI. Basically, you have to use SoapUI to generate Request XML and after that, you can replace parameters as needed in the generated body.

What is SOAP Web Service?

If you are new to SOAP Web Service sometimes referred as XML Web Service then please read some concept about SOAP Web service standard from this link There are two important aspects in SOAP Web service.

1. Getting WSDL file or URL
2. Knowing exact Web Service URL

What is WSDL

In very simple term WSDL (often pronounced as whiz-dull) is nothing but a document which describes Service metadata (e.g. Functions you can call, Request parameters, response structure etc). Some service simply give you WSDL as xml file you can download on local machine and then analyze or sometimes you may get direct URL (e.g. http://api.mycompany.com/hr-soap-service/?wsdl )

Example SQL Query for SOAP API call using ZappySys XML Driver

Here is an example SQL query you can write to call SOAP API. If you not sure about many details then check next few sections on how to use XML Driver User Interface to build desired SQL query to POST data to XML SOAP Web Service without any coding.

SELECT * FROM $
WITH(
	 Src='http://www.holidaywebservice.com/HolidayService_v2/HolidayService2.asmx'
	,DataConnectionType='HTTP'
	,CredentialType='Basic' --OR SoapWss
	,SoapWssPasswordType='PasswordText'
	,UserName='myuser'
	,Password='pass$$w123'
	,Filter='$.soap:Envelope.soap:Body.GetHolidaysAvailableResponse.GetHolidaysAvailableResult.HolidayCode[*]'
	,ElementsToTreatAsArray='HolidayCode'	
	,RequestMethod='POST'	
	,Header='Content-Type: text/xml;charset=UTF-8 || SOAPAction: "http://www.holidaywebservice.com/HolidayService_v2/GetHolidaysAvailable"'
	,RequestData='
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:hol="http://www.holidaywebservice.com/HolidayService_v2/">
   <soapenv:Header/>
   <soapenv:Body>
      <hol:GetHolidaysAvailable>
         <!--type: Country - enumeration: [Canada,GreatBritain,IrelandNorthern,IrelandRepublicOf,Scotland,UnitedStates]-->
         <hol:countryCode>UnitedStates</hol:countryCode>
      </hol:GetHolidaysAvailable>
   </soapenv:Body>
</soapenv:Envelope>'
)

Now let's look at steps to create SQL query to call SOAP API. Later we will see how to generate code for your desired programming language (e.g. C# or SQL Server)

Video Tutorial - Introduction to SOAP Web Service and SoapUI tool

Before we dive into details about calling SOAP API using ZappySys XML Driver, lets first understand what is SOAP API and how to create SOAP requests using SoapUI tool. You will learn more about this process in the later section. The video contains some fragment about using SOAP API in SSIS but just ignore that part because we will be calling Soap API using ZappySys ODBC Driver rather than SSIS Components.  

Using SoapUI to test SOAP API call / Create Request Body XML

Assuming you have downloaded and installed SoapUI from here, now we are ready to use WSDL for your SOAP Web Service Calls. If you do not have WSDL file or URL handy then contact your API provider (sometimes you just have to add ?wsdl at the end of your Service URL to get WSDL so try that. Example: http://mycompany/myservice?wsdl ). If you don't know what is WSDL then in short, WSDL is Web service Description Language (i.e. XML file which describes your SOAP Service). WSDL helps to craft SOAP API request Body for ZappySys XML Driver. So Let's get started.

1. Open SoapUI and click SOAP button to create new SOAP Project
2. Enter WSDL URL or File Path of WSDLFor example WSDL for our sample service can be accessed via this URL

   http://www.dneonline.com/calculator.asmx?wsdl

   
   Create new SOAP API Project in SoapUI tool for SOAP API Testing
3. Once WSDL is loaded you will see possible operations you can call for your SOAP Web Service.
4. If your web service requires credentials then you have to configure it. There are two common credential types for public services (SOAP WSS or BASIC )
   1. To use SOAP WSS Credentials select request node and enter UserId, Password, and WSS-PasswordType (PasswordText or PasswordHash)
      
      Configure SOAP WSS Credentials for SoapUI (SOAP API Testing Tool)
   2. To use BASIC Auth Credentials select request node and double-click it. At the bottom click on Auth (Basic) and From Authorization dropdown click Add New and Select Basic.
      Configure Basic Authorization for SoapUI (SOAP API Testing Tool)
5. Now you can test your request first Double-click on the request node to open request editor.
6. Change necessary parameters, remove optional or unwanted parameters. If you want to regenerate request you can click on Recreate default request toolbar icon.
   Create SOAP Request XML (With Optional Parameters)
7. Once your SOAP Request XML is ready, Click the Play button in the toolbar to execute SOAP API Request and Response will appear in Right side panel. Test SOAP API using SoapUI Tool (Change Default XML Body / Parameters, Execute and See Response)

Create DSN using ZappySys XML Driver to call SOAP API

Once you have tested your SOAP API in SoapUI tool, we are ready to use ZappySys XML driver to call SOAP API in your preferred BI tool or Programming language.

1. First open ODBC Data Sources (search ODBC in your start menu or go under ZappySys > ODBC PowerPack > ODBC 64 bit)
2. Goto System DSN Tab (or User DSN which is not used by Service account)
3. Click Add and Select ZappySys XML Driver ZappySys ODBC Driver for XML / SOAP API
4. Configure API URL, Request Method and Request Body as below ZappySys XML Driver - Calling SOAP API - Configure URL, Method, Body
5. (This step is Optional) If your SOAP API requires credentials then Select Connection Type to HTTP and configure as below.
   ZappySys XML Driver - Configure SOAP WSS Credentials or Basic Authorization (Userid, Password)
6. Configure-Request Headers as below (You can get it from Request > Raw tab from SoapUI after you test the request by clicking the Play button) Configure SOAP API Request Headers - ZappySys XML Driver
7. Once credentials entered you can select Filter to extract data from the desired node. Make sure to select array node (see special icon) or select the node which contains all necessary columns if you don't have array node. Select Filter - Extract data from nested XML / SOAP API Response (Denormalize Hierarchy)
8. If prompted select yes to treat selected node as Array (This is helpful when you expect one or more record for selected node) Treat selected node as XML Array Option for SOAP API Response XML

Preview SOAP API Response / Generate SQL Code for SOAP API Call

Once you configure settings for XML Driver now you can preview data or generate example code for desired language (e.g. C#, Python, Java, SQL Server). Go to Preview tab and you will see default query generated based on settings you entered in previous sections. Attributes listed in WITH clause are optional. If you omit attribute in WITH clause it will use it from Properties tab.

Preview Data

Preview SOAP API Response in ZappySys XML Driver

Generate Code Option