Using Multi-Model with Python and Node.js

In this exercise, we will use Python, JavaScript, and InterSystems ObjectScript to interact with the data from different contexts, following these steps:

1. Use Python to create a table schema using standard SQL statements.
2. Modify the underlying ObjectScript class for that table to allow it to receive and persist JSON data directly.
3. Create a simple Node.js application that will send JSON files to the instance of InterSystems IRIS.
4. Query that database using Python again to see how the same data could be accessed in multiple languages from multiple contexts.

Get set up

1. First, make sure you have an instance of InterSystems IRIS and an IDE ready to go. Sandbox settings will appear below after you log in and launch a sandbox.
   

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2. Open the InterSystems IRIS sandbox IDE and clone this repository: git clone -b try-iris https://github.com/intersystems/multi-model-exercise.
3. Open the connections.config file in the top-level directory and update the IP equal to -- cannot display value - please provision a sandbox and change the value of port to -- cannot display value - please provision a sandbox. Then click Save.

Create the table schema using Python

1. Install and configure Python.
   • Run cd /home/project/multi-model-exercise/python.
   • Run sudo odbcinst -i -d -f pyodbc_wheel/odbcinst.ini.
2. Open python/createSchema.py and scroll down to the create_employee function. Below the function declaration, uncomment the following code:

   create_employee = """
   	CREATE TABLE Demo.Employee(
   	    ID Integer PRIMARY KEY AUTO_INCREMENT,
   	    Name varchar(256),
   	    Title varchar(256), 
   	    Department varchar(50)
   	)
       """
   

   As you can see, this is a standard SQL create statement that will generate an Employee table on your InterSystems IRIS instance.

3. Run python createSchema.py. If successful, the terminal will output Created table Demo.Employee successfully.
4. Confirm that the Demo.Employee table has been created.
   • Open the Management Portal by clicking InterSystems > Management Portal at the top of your sandbox IDE.
   • Navigate to System Explorer > SQL and expand the Tables section. Find Demo.Employee in the list.

Modify the table class using InterSystems ObjectScript

Setting up the Visual Studio Code ObjectScript Extension

1. Install InterSystems Visual Studio Code if you have not already done so.
2. Open Visual Studio Code. In the Extensions Manager, search for and install the InterSystems ObjectScript extension.
3. Select a folder for your workspace by selecting Open Folder in the File Explorer, or File > Open. Select or create a folder on your local machine to store settings specific to your workspace.
4. Open your Visual Studio Code settings by clicking File (or Code if on macOS) > Preferences > Settings > InterSystems ObjectScript. Then select Workspace > Edit in settings.json (under “Objectscript: Conn”). Paste the following, filling in the settings for your InterSystems IRIS instance connection:

   {
   	"objectscript.conn": {
   		"active": true, 
   		"label": "LOCAL",
   		"host": "-- cannot display value - please provision a sandbox"
   		"port": -- cannot display value - please provision a sandbox
   		"username": "tech",
   		"password": "demo",
   		"ns": "USER", // the namespace you wish to connect to
   		"https": false
   	}
   }

    

5. Navigate to the ObjectScript: Explorer pane by clicking on the InterSystems logo on the left side of your Visual Studio Code window, right-click Classes/Demo/Employee.cls and select Export.
6. Navigate to the Explorer pane and open the newly created src/Demo/Employee.cls file.

Modifying classes with Visual Studio Code

1. At the top of the Demo.Employee class, change Extends %Persistent to Extends (%Persistent, %JSON.Adaptor).
   InterSystems ObjectScript is an object-oriented programming language that supports multiple inheritance. This means that by inheriting the %JSON.Adaptor class, your table is now automatically able to import JSON data into instances. For more information on the %JSON.Adaptor class, read Using the JSON Adaptor.
2. Because our table includes an auto-incremented primary key, we need to tell the JSON.Adaptor class not to look for that field in incoming JSON files, but to output it as a field when exporting class instances to JSON format. To do this, find the ID property in the Employee class and add (%JSONINCLUDE = "outputonly") after %Library.AutoIncrement.
3. Before we can run this file, we need to add one small class method to expose the functionality of the %JSON.Adaptor class to the Native API — and, by extension, to our Node.js application. Below the Property and Parameter declarations in the Demo.Employee class, paste the following code:

   ClassMethod fromJSON(jsonString as %String) As %Status
   {
   	set employee = ..%New() 		//create a new class instance
   	do employee.%JSONImport(jsonString) 	//call the %JSON.Adapter instance method to import JSON string
   	set employee.ID = 0 			//this field must be set to 0 for the %Library.AutoIncrement class to increment correctly
   	set status =  employee.%Save() 		//this persists the instance
   
   	return status
   }
   

4. Make sure to recompile the Demo.Employee class by saving it. You have now configured your SQL table class to receive JSON data and automatically create a new record from it.
   Note that the completed ObjectScript Employee class is included in this repository for your reference at ObjectScript/Demo.Employee.cls.

Create a Node.js app to send JSON files to your database

1. Return to your InterSystems IRIS sandbox IDE and run cd /home/project/multi-model-exercise/nodeApp.
2. Create a new file called record.json containing the following JSON object:

   {
   	"Name": "JJ Smith",
   	"Title": "Software Engineer",
   	"Department": "Engineering"
   }
   

3. Run npm install --save intersystems-iris-native. This installs the InterSystems IRIS Native API, which enables you to both access the underlying data structures in your database, and to call ObjectScript class methods directly from your code.
4. Open the app.js file. Navigate to const Iris = connection.createIris() and uncomment the following lines:

   let record = JSON.parse(fs.readFileSync("./record.json", "utf8"))
   Iris.classMethodValue("Demo.Employee", "fromJSON", JSON.stringify(record))
   console.log(`Created new record in Demo.Employee table.`)
   

   This code calls a class method using the Native API and passes a JSON string as a parameter. For more information, see Calling ObjectScript Methods and Functions

5. In the terminal, type node app.js. The node application will output that it has created a new record.
   
   

   Note:

   If you get a “Method does not exist” error message, make sure you clicked Save in Visual Studio Code after modifying the Demo.Employee class.

Query the database with Python

14. cd back in the Python directory  (cd /home/project/multi-model-exercise/python).
15. Run python query.py. You should see the results of the SQL query, which includes the record of JJ Smith that you inserted using Node.js.