Writing Azure Functions in Clojure

core.clj

(ns com.github.hindol.clj-fn.core
  (:import
   (com.microsoft.azure.functions ExecutionContext
                                  HttpRequestMessage
                                  HttpResponseMessage
                                  OutputBinding)
   (com.microsoft.azure.functions.annotation FunctionName
                                             HttpTrigger
                                             QueueOutput)))

;; Bug: https://clojure.atlassian.net/browse/CLJ-2269
;; Must fully qualify type hints on definterface.
(definterface Functional
  (^com.microsoft.azure.functions.HttpResponseMessage
   run
   [^com.microsoft.azure.functions.HttpRequestMessage
    request
    ^com.microsoft.azure.functions.OutputBinding
    message
    ^com.microsoft.azure.functions.ExecutionContext
    context]))

(deftype Function []
  Functional
  (^{:tag         HttpResponseMessage
     FunctionName "HttpExample"}
    run
    [this
     ^{:tag        HttpRequestMessage
        HttpTrigger {:name      "req"
                     :methods   [HttpMethod/GET HttpMethod/POST]
                     :authLevel AuthorizationLevel/ANONYMOUS}}
     request
     ^{:tag        OutputBinding
       QueueOutput {:name       "msg"
                    :queueName  "outqueue"
                    :connection "AzureWebJobsStorage"}}
     message
     ^ExecutionContext
     context]
    42))

Function.java

package com.github.hindol.clj_fn.core;

import clojure.lang.*;
import com.microsoft.azure.functions.*;
import com.microsoft.azure.functions.annotation.*;

public final class Function implements Functional, IType
{
    public static final Object const__0;
    
    public static IPersistentVector getBasis() {
        return Tuple.create();
    }
    
    @FunctionName("HttpExample")
    public HttpResponseMessage run(@HttpTrigger(name = "req", methods = { HttpMethod.GET, HttpMethod.POST }, authLevel = AuthorizationLevel.ANONYMOUS) final HttpRequestMessage request, @QueueOutput(name = "msg", queueName = "outqueue", connection = "AzureWebJobsStorage") final OutputBinding message, final ExecutionContext context) {
        return (HttpResponseMessage)Function.const__0;
    }
    
    static {
        const__0 = 42L;
    }
}

Functional.java

package com.github.hindol.clj_fn.core;

import com.microsoft.azure.functions.ExecutionContext;
import com.microsoft.azure.functions.HttpRequestMessage;
import com.microsoft.azure.functions.HttpResponseMessage;
import com.microsoft.azure.functions.OutputBinding;

public interface Functional {
  HttpResponseMessage run(HttpRequestMessage paramHttpRequestMessage, OutputBinding paramOutputBinding, ExecutionContext paramExecutionContext);
}

Trying to re-create the example from: https://docs.microsoft.com/en-us/azure/azure-functions/functions-create-first-azure-function-azure-cli?tabs=bash%2Cbrowser&pivots=programming-language-java

package com.function;

import java.util.*;
import com.microsoft.azure.functions.annotation.*;
import com.microsoft.azure.functions.*;

/**
 * Azure Functions with HTTP Trigger.
 */
public class Function {
    /**
     * This function listens at endpoint "/api/HttpExample". Two ways to invoke it using "curl" command in bash:
     * 1. curl -d "HTTP Body" {your host}/api/HttpExample
     * 2. curl "{your host}/api/HttpExample?name=HTTP%20Query"
     */
    @FunctionName("HttpExample")
    public HttpResponseMessage run(
            @HttpTrigger(name = "req", methods = {HttpMethod.GET, HttpMethod.POST}, authLevel = AuthorizationLevel.ANONYMOUS) 
            HttpRequestMessage<Optional<String>> request, 
            @QueueOutput(name = "msg", queueName = "outqueue", 
            connection = "AzureWebJobsStorage") OutputBinding<String> msg, 
            final ExecutionContext context) {
        context.getLogger().info("Java HTTP trigger processed a request.");

        // Parse query parameter
        String query = request.getQueryParameters().get("name");
        String name = request.getBody().orElse(query);

        if (name == null) {
            return request.createResponseBuilder(HttpStatus.BAD_REQUEST)
            .body("Please pass a name on the query string or in the request body").build();
        } else {
            // Write the name to the message queue. 
            msg.setValue(name);

            return request.createResponseBuilder(HttpStatus.OK).body("Hello, " + name).build();
        }
    }
}

Check hindol/clj-fn@d3baaae for an alternative Maven based approach to calling Clojure code from Azure Functions.