Auf eine Wertänderung durch Aktualisierung eines Werts reagieren

Aktualisiert einen Wert immer dann, wenn er in Firestore geändert wird.

Dokumentationsseiten mit diesem Codebeispiel

Die folgenden Dokumente enthalten das Codebeispiel im Kontext:



using CloudNative.CloudEvents;
using Google.Cloud.Firestore;
using Google.Cloud.Functions.Framework;
using Google.Cloud.Functions.Hosting;
using Google.Events.Protobuf.Cloud.Firestore.V1;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;

namespace FirestoreReactive
    public class Startup : FunctionsStartup
        public override void ConfigureServices(WebHostBuilderContext context, IServiceCollection services) =>

    // Register the startup class to provide the Firestore dependency.
    public class Function : ICloudEventFunction<DocumentEventData>
        private readonly ILogger _logger;
        private readonly FirestoreDb _firestoreDb;

        public Function(ILogger<Function> logger, FirestoreDb firestoreDb) =>
            (_logger, _firestoreDb) = (logger, firestoreDb);

        public async Task HandleAsync(CloudEvent cloudEvent, DocumentEventData data, CancellationToken cancellationToken)
            // Get the recently-written value. This expression will result in a null value
            // if any of the following is true:
            // - The event doesn't contain a "new" document
            // - The value doesn't contain a field called "original"
            // - The "original" field isn't a string
            string currentValue = data.Value?.ConvertFields().GetValueOrDefault("original") as string;
            if (currentValue is null)
                _logger.LogWarning($"Event did not contain a suitable document");

            string newValue = currentValue.ToUpperInvariant();
            if (newValue == currentValue)
                _logger.LogInformation("Value is already upper-cased; no replacement necessary");

            // The CloudEvent subject is "documents/x/y/...".
            // The Firestore SDK FirestoreDb.Document method expects a reference relative to
            // "documents" (so just the "x/y/..." part). This may be simplified over time.
            if (cloudEvent.Subject is null || !cloudEvent.Subject.StartsWith("documents/"))
                _logger.LogWarning("CloudEvent subject is not a document reference.");
            string documentPath = cloudEvent.Subject.Substring("documents/".Length);

            _logger.LogInformation("Replacing '{current}' with '{new}' in '{path}'", currentValue, newValue, documentPath);
            await _firestoreDb.Document(documentPath).UpdateAsync("original", newValue);


// Package upper contains a Firestore Cloud Function.
package upper

import (

	firebase ""

// FirestoreEvent is the payload of a Firestore event.
type FirestoreEvent struct {
	OldValue   FirestoreValue `json:"oldValue"`
	Value      FirestoreValue `json:"value"`
	UpdateMask struct {
		FieldPaths []string `json:"fieldPaths"`
	} `json:"updateMask"`

// FirestoreValue holds Firestore fields.
type FirestoreValue struct {
	CreateTime time.Time `json:"createTime"`
	// Fields is the data for this value. The type depends on the format of your
	// database. Log an interface{} value and inspect the result to see a JSON
	// representation of your database fields.
	Fields     MyData    `json:"fields"`
	Name       string    `json:"name"`
	UpdateTime time.Time `json:"updateTime"`

// MyData represents a value from Firestore. The type definition depends on the
// format of your database.
type MyData struct {
	Original struct {
		StringValue string `json:"stringValue"`
	} `json:"original"`

// GOOGLE_CLOUD_PROJECT is automatically set by the Cloud Functions runtime.
var projectID = os.Getenv("GOOGLE_CLOUD_PROJECT")

// client is a Firestore client, reused between function invocations.
var client *firestore.Client

func init() {
	// Use the application default credentials.
	conf := &firebase.Config{ProjectID: projectID}

	// Use context.Background() because the app/client should persist across
	// invocations.
	ctx := context.Background()

	app, err := firebase.NewApp(ctx, conf)
	if err != nil {
		log.Fatalf("firebase.NewApp: %v", err)

	client, err = app.Firestore(ctx)
	if err != nil {
		log.Fatalf("app.Firestore: %v", err)

// MakeUpperCase is triggered by a change to a Firestore document. It updates
// the `original` value of the document to upper case.
func MakeUpperCase(ctx context.Context, e FirestoreEvent) error {
	fullPath := strings.Split(e.Value.Name, "/documents/")[1]
	pathParts := strings.Split(fullPath, "/")
	collection := pathParts[0]
	doc := strings.Join(pathParts[1:], "/")

	curValue := e.Value.Fields.Original.StringValue
	newValue := strings.ToUpper(curValue)
	if curValue == newValue {
		log.Printf("%q is already upper case: skipping", curValue)
		return nil
	log.Printf("Replacing value: %q -> %q", curValue, newValue)

	data := map[string]string{"original": newValue}
	_, err := client.Collection(collection).Doc(doc).Set(ctx, data)
	if err != nil {
		return fmt.Errorf("Set: %v", err)
	return nil


import java.util.HashMap;
import java.util.Locale;
import java.util.Map;
import java.util.concurrent.ExecutionException;
import java.util.logging.Level;
import java.util.logging.Logger;

public class FirebaseFirestoreReactive implements RawBackgroundFunction {

  // Use GSON ( to parse JSON content.
  private static final Gson gson = new Gson();

  private static final Logger logger = Logger.getLogger(FirebaseFirestoreReactive.class.getName());
  private static final Firestore FIRESTORE = FirestoreOptions.getDefaultInstance().getService();

  private final Firestore firestore;

  public FirebaseFirestoreReactive() {

  FirebaseFirestoreReactive(Firestore firestore) {
    this.firestore = firestore;

  public void accept(String json, Context context) {
    // Get the recently-written value
    JsonObject body = gson.fromJson(json, JsonObject.class);
    JsonObject tempJson = body.getAsJsonObject("value");

    // Verify that value.fields.original.stringValue exists
    String currentValue = null;
    if (tempJson != null) {
      tempJson = tempJson.getAsJsonObject("fields");
    if (tempJson != null) {
      tempJson = tempJson.getAsJsonObject("original");
    if (tempJson != null && tempJson.has("stringValue")) {
      currentValue = tempJson.get("stringValue").getAsString();
    if (currentValue == null) {
      throw new IllegalArgumentException("Malformed JSON: " + json);

    // Convert recently-written value to ALL CAPS
    String newValue = currentValue.toUpperCase(Locale.getDefault());

    // Update Firestore DB with ALL CAPS value
    Map<String, String> newFields = Map.of("original", newValue);

    String affectedDoc = context.resource().split("/documents/")[1].replace("\"", "");

    if (!currentValue.equals(newValue)) {
      // The stored value needs to be updated
      // Write the upper-cased value to Firestore"Replacing value: %s --> %s", currentValue, newValue));
      try {
        FIRESTORE.document(affectedDoc).set(newFields, SetOptions.merge()).get();
      } catch (ExecutionException | InterruptedException e) {
        logger.log(Level.SEVERE, "Error updating Firestore document: " + e.getMessage(), e);
    } else {
      // The stored value is already upper-case, and doesn't need updating.
      // (Don't perform a "second" write, since that could trigger an infinite loop.)"Value is already upper-case."));


const Firestore = require('@google-cloud/firestore');

const firestore = new Firestore({
  projectId: process.env.GOOGLE_CLOUD_PROJECT,

// Converts strings added to /messages/{pushId}/original to uppercase
exports.makeUpperCase = event => {
  const resource =;
  const affectedDoc = firestore.doc(resource.split('/documents/')[1]);

  const curValue = event.value.fields.original.stringValue;
  const newValue = curValue.toUpperCase();

  if (curValue !== newValue) {
    console.log(`Replacing value: ${curValue} --> ${newValue}`);

    return affectedDoc.set({
      original: newValue,
  } else {
    // Value is already upper-case
    // Don't perform a(nother) write to avoid infinite loops
    console.log('Value is already upper-case.');


use Google\Cloud\Firestore\FirestoreClient;
use Google\CloudFunctions\CloudEvent;

function firebaseReactive(CloudEvent $cloudevent)
    $log = fopen(getenv('LOGGER_OUTPUT') ?: 'php://stderr', 'wb');
    $data = $cloudevent->getData();

    $resource = $data['value']['name'];

    $db = new FirestoreClient();

    $docPath = explode('/documents/', $resource)[1];

    $affectedDoc = $db->document($docPath);

    $curValue = $data['value']['fields']['original']['stringValue'];
    $newValue = strtoupper($curValue);

    if ($curValue !== $newValue) {
        fwrite($log, 'Replacing value: ' . $curValue . ' --> ' . $newValue . PHP_EOL);

        $affectedDoc->set(['original' => $newValue]);
    } else {
        // Value is already upper-case
        // Don't perform another write (it might cause an infinite loop)
        fwrite($log, 'Value is already upper-case.' . PHP_EOL);


from import firestore
client = firestore.Client()

# Converts strings added to /messages/{pushId}/original to uppercase
def make_upper_case(data, context):
    path_parts = context.resource.split('/documents/')[1].split('/')
    collection_path = path_parts[0]
    document_path = '/'.join(path_parts[1:])

    affected_doc = client.collection(collection_path).document(document_path)

    cur_value = data["value"]["fields"]["original"]["stringValue"]
    new_value = cur_value.upper()

    if cur_value != new_value:
        print(f'Replacing value: {cur_value} --> {new_value}')
            u'original': new_value
        # Value is already upper-case
        # Don't perform a second write (which can trigger an infinite loop)
        print('Value is already upper-case.')


require "functions_framework"

FunctionsFramework.on_startup do
  # Lazily construct a Firestore client when needed, and reuse it on
  # subsequent calls.
  set_global :firestore_client do
    require "google/cloud/firestore" project_id: ENV["GOOGLE_CLOUD_PROJECT"]

# Converts strings added to /messages/{pushId}/original to uppercase
FunctionsFramework.cloud_event "make_upper_case" do |event|
  # Event-triggered Ruby functions receive a CloudEvents::Event::V1 object.
  # See
  # The Firebase event payload can be obtained from the event data.
  cur_value =["value"]["fields"]["original"]["stringValue"]

  # Compute new value and determine whether it needs to be modified.
  # If the value is already upper-case, don't perform another write,
  # to avoid infinite loops.
  new_value = cur_value.upcase
  if cur_value == new_value "Value is already upper-case"

  # Use the Firestore client library to update the value.
  # The document name can be obtained from the event subject. "Replacing value: #{cur_value} --> #{new_value}"
  doc_name = event.subject.split("documents/").last
  affected_doc = global(:firestore_client).doc doc_name
  new_doc_data = { original: new_value }
  affected_doc.set new_doc_data

Nächste Schritte

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