Invoking FunctionGraph

This example demonstrates how to call a FunctionGraph implemented in python using java.

Prerequisites

To run java example following environment variables should be set:

Environtment Variables

Name	Description	Example
OTC_USER_NAME	User name	John Doe
OTC_USER_PASSWORD	User password	JOHNDOESPASSWORT
OTC_SDK_PROJECTID	Project Id	87b7f28e70c14498b3c243af5b4#####
OTC_DOMAIN_NAME	Domain name (Account ID)	OTC-EU-DE-000000000010000#####
OTC_TENANT_NAME	Tenant name (Region)	eu-de
OTC_AUTH_URL	IAM Endpoint	https://iam.eu-de.otc.t-systems.com

Example FunctionGraph written in python

Example FunctionGraph: functionGraph.py

# -*- coding:utf-8 -*-
import json
def handler (event, context):
  return {
    "statusCode": 200,
    "isBase64Encoded": False,
    "body": json.dumps(event),
    "headers": {
    "Content-Type": "application/json"
    }
  }

Deploy this FunctionGraph as follows:

• Type: “Event Function”:

• Name: “InvokeSamplePython”

• Agency: “Use no agency”

• Runtime: “python 3.10”

Invoking FunctionGraph using Java

For authorization, see Making an API Request

For Function Execution, see Executing a Function Synchronously

Note

Supported Java Version 11 and above.

InvokeFG.javaConstants.java

/*
 * Copyright (c) 2025 T-Systems International GmbH.
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.opentelekomcloud.samples;

import java.net.ProxySelector;
import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpRequest.BodyPublishers;
import java.net.http.HttpResponse;
import java.net.http.HttpResponse.BodyHandlers;
import java.util.Optional;

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
import com.google.gson.JsonParser;

/**
 * InvokeFG is a sample function that demonstrates how to invoke a FunctionGraph function
 * using the OpenTelekomCloud FunctionGraph service.
 * It retrieves an authentication token, constructs an HTTP request, and processes the response.
 */
public class InvokeFG {

  private static final Gson gsonPrettyPrint = new GsonBuilder().setPrettyPrinting().create();

  /**
   * Get user token through username/password-based authentication
   *
   * @see <a href="https://docs.otc.t-systems.com/function-graph/api-ref/calling_apis/making_an_api_request.html">Making an api request</a>
   * @return token
   */
  private static String getAuthToken() throws Exception {

    HttpClient client = HttpClient.newBuilder()
        .proxy(ProxySelector.getDefault()) // use system default proxy
        .build();

    // prettier-ignore
    String authBody = ""
        + "{"
        + "   \"auth\": {"
        + "    \"identity\": {"
        + "       \"methods\": [ \"password\" ],"
        + "       \"password\": {"
        + "         \"user\": {"
        + "           \"name\": \"" + Constants.getInstance().getUserName() + "\","
        + "           \"password\": \"" + Constants.getInstance().getUserPassword() + "\","
        + "           \"domain\": { \"name\": \"" + Constants.getInstance().getAccountName() + "\"}"
        + "         }"
        + "       }"
        + "    },"
        + "    \"scope\": { \"domain\": { \"name\": \"" + Constants.getInstance().getAccountName() + "\" },"
        + "                 \"project\": { \"id\": \"" + Constants.getInstance().getProjectId() + "\" }"
        + "    }"
        + "  }"
        + "}";

    System.out.println(authBody);

    HttpRequest request = HttpRequest.newBuilder()
        .uri(URI.create(Constants.getInstance().getTokenUri()))
        .header("Content-Type", "application/json;charset=utf8")
        .POST(BodyPublishers.ofString(authBody))
        .build();

    HttpResponse<String> response = client.send(request, BodyHandlers.ofString());

    if (response.statusCode() != 201) {

        if (response.statusCode() == 401) {
            throw new Exception(
                    String.format("Get Token failed with: %s", "Unauthorized"));
        }
        JsonElement jsonElement = JsonParser.parseString(response.body());

        JsonElement error_code = jsonElement.getAsJsonObject().get("error_code");
        JsonElement error_msg = jsonElement.getAsJsonObject().get("error_msg");

        throw new Exception(
                String.format("Get Token failed with: %s, %s, %s", response.statusCode(), error_code, error_msg));
    }

    System.out.println(response.body());

    Optional<String> token = response.headers().firstValue("x-subject-token");

    if (!token.isPresent()) {
      throw new Exception("x-subject-token to present in header");
    }

    return token.get();

  }

  public static void main(String[] args) {

    try {
      String token = getAuthToken();

      HttpClient client = HttpClient.newBuilder()
          .proxy(ProxySelector.getDefault())
          .build();

      String invokeUri = Constants.getInstance().getInvokeUri("InvokeSamplePython");

      String requestBody = "{ \"key\": \"Hello world of OpenTelekomCloud\"}";

      HttpRequest request = HttpRequest.newBuilder()
          .uri(URI.create(invokeUri))
          .header("Content-Type", "application/json;charset=utf8")
          .header("X-AUTH-Token", token)
          // X-Cff-Log-Type:
          // "tail": 4KB logs will be returned
          // "": no logs will be returned
          .header("X-Cff-Log-Type", "tail")
          // X-CFF-Request-Version:
          // "v0" response body in text format
          // "v1" response body in json format
          .header("X-CFF-Request-Version", "v1")
          .POST(BodyPublishers.ofString(requestBody))
          .build();

      HttpResponse<String> response = client.send(request, BodyHandlers.ofString());

      System.out.println("Status code of invoke request: " + response.statusCode());

      JsonElement jsonElement = JsonParser.parseString(response.body());

      System.out.println("Complete response:");
      System.out.println("==================");
      System.out.println(gsonPrettyPrint.toJson(jsonElement));

      JsonElement result = jsonElement.getAsJsonObject().get("result");

      JsonObject o = JsonParser.parseString(result.getAsString()).getAsJsonObject();
      System.out.println("Response body:");
      System.out.println("==============");
      System.out.println(o.get("body").getAsString());

      JsonElement log = jsonElement.getAsJsonObject().get("log");
      System.out.println("Log:");
      System.out.println("==============");
      System.out.println(log.getAsString());
    } catch (Exception e) {
      e.printStackTrace();
    }
  }

}

last updated: 2025-09-23 09:31:56 UTC - commit: 70dfd27683766d95e95edd34387e5c0f102dbc02