How to set Java runtime stack for Azure Linux App Service using Terraform

I'm trying to configure the Java runtime stack for an Azure Linux App Service using Terraform.

I followed the Terraform documentation for azurerm_linux_web_app and configured the java_server, java_server_version, and java_version values according to the output of az webapp list-runtimes --os-type linux

1- First try

Here's my current Terraform code:

    resource "azurerm_linux_web_app" "app_service" {
      site_config {
         application_stack {
           java_server         = "JAVA"
           java_server_version = "java21"
           java_version        = "21"
          }
          app_command_line = "java -jar /home/site/wwwroot/app.jar"
        }
     }

However, after deploying, the Runtime Stack section in the Azure portal shows an empty configuration (see this screenshot).

2- Second:

I came across this related GitHub issue, which say that the linux_fx_version property can be set to fix this. So i updated my code, and tried with this:

    resource "azurerm_linux_web_app" "app_service" {
      site_config {
          linux_fx_version="JAVA|21"
          app_command_line = "java -jar /home/site/wwwroot/app.jar"
        }
     }

However, in the newer versions of the azurerm_linux_web_app resource, this property is now computed and can no longer be set manually.

╷
│ Error: Value for unconfigurable attribute
│ 
│   with module.compute.azurerm_linux_web_app.app_service,
│   on modules\004-compute\main.tf line 20, in resource "azurerm_linux_web_app" "app_service":
│   20:     linux_fx_version = "JAVA|21"
│ 
│ Can't configure a value for "site_config.0.linux_fx_version": its value will be decided automatically based on the result of applying this configuration.

Set Java runtime stack for Azure Linux App Service using Terraform

Continuation from the comment section the newer Terraform providers, i.e., after azurerm 3.40+, linux_fx_version is computed internally you cannot manually set linux_fx_version anymore.

Now, Terraform automatically builds linux_fx_version based on the fields you specify inside application_stack {}.

Configuration:

resource "azurerm_linux_web_app" "app_service" {
  name                = "your-linux-webapp"
  resource_group_name = azurerm_resource_group.this.name
  location            = azurerm_resource_group.this.location
  service_plan_id     = azurerm_service_plan.this.id

  site_config {
    application_stack {
      java_server         = "JAVA"
      java_server_version = "21" 
      java_version        = "21"  
    }
    app_command_line = "java -jar /home/site/wwwroot/app.jar"
  }
}

Refer:

https://registry.terraform.io/providers/hashicorp/azurerm/latest/docs/resources/linux_web_app#application_stack-1