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Salvo quando diversamente specificato, i contenuti di questa pagina sono concessi in base alla licenza Creative Commons Attribution 4.0, mentre gli esempi di codice sono concessi in base alla licenza Apache 2.0. Per ulteriori dettagli, consulta le norme del sito di Google Developers. Java è un marchio registrato di Oracle e/o delle sue consociate.
[[["Facile da capire","easyToUnderstand","thumb-up"],["Il problema è stato risolto","solvedMyProblem","thumb-up"],["Altra","otherUp","thumb-up"]],[["Difficile da capire","hardToUnderstand","thumb-down"],["Informazioni o codice di esempio errati","incorrectInformationOrSampleCode","thumb-down"],["Mancano le informazioni o gli esempi di cui ho bisogno","missingTheInformationSamplesINeed","thumb-down"],["Problema di traduzione","translationIssue","thumb-down"],["Altra","otherDown","thumb-down"]],[],[[["\u003cp\u003eThis content demonstrates how to use transactions in Google Cloud Datastore to either retrieve an existing entity or create a new one if it doesn't exist.\u003c/p\u003e\n"],["\u003cp\u003eCode samples are provided in C#, Go, Java, Node.js, PHP, Python, and Ruby, illustrating the process of getting or creating an entity within a transaction.\u003c/p\u003e\n"],["\u003cp\u003eThe examples show how to look up an entity using its key and how to insert or save the entity into the database using the \u003ccode\u003etransaction\u003c/code\u003e class functions.\u003c/p\u003e\n"],["\u003cp\u003eThe content links to the documentation for Cloud Datastore transactions, as well as instructions for setting up client libraries and authentication.\u003c/p\u003e\n"],["\u003cp\u003eThe page also provides links to the specific API reference documentation for each of the languages showcased in the samples.\u003c/p\u003e\n"]]],[],null,["# Get or create in a transaction.\n\nExplore further\n---------------\n\n\nFor detailed documentation that includes this code sample, see the following:\n\n- [Cloud Datastore Transactions](/datastore/docs/concepts/cloud-datastore-transactions)\n- [Transactions](/datastore/docs/concepts/transactions)\n\nCode sample\n-----------\n\n### C#\n\n\nTo learn how to install and use the client library for Datastore mode, see\n[Datastore mode client libraries](/datastore/docs/reference/libraries).\n\n\nFor more information, see the\n[Datastore mode C# API\nreference documentation](https://cloud.google.com/dotnet/docs/reference/Google.Cloud.Datastore.V1/latest).\n\n\nTo authenticate to Datastore mode, set up Application Default Credentials.\nFor more information, see\n\n[Set up authentication for a local development environment](/docs/authentication/set-up-adc-local-dev-environment).\n\n Entity task;\n using (var transaction = _db.BeginTransaction())\n {\n task = transaction.Lookup(_sampleTask.Key);\n if (task == null)\n {\n transaction.Insert(_sampleTask);\n transaction.Commit();\n }\n }\n\n### Go\n\n\nTo learn how to install and use the client library for Datastore mode, see\n[Datastore mode client libraries](/datastore/docs/reference/libraries).\n\n\nFor more information, see the\n[Datastore mode Go API\nreference documentation](https://cloud.google.com/go/docs/reference/cloud.google.com/go/datastore/latest).\n\n\nTo authenticate to Datastore mode, set up Application Default Credentials.\nFor more information, see\n\n[Set up authentication for a local development environment](/docs/authentication/set-up-adc-local-dev-environment).\n\n _, err := client.RunInTransaction(ctx, func(tx *datastore.Transaction) error {\n \tvar task Task\n \tif err := tx.Get(key, &task); err != datastore.ErrNoSuchEntity {\n \t\treturn err\n \t}\n \t_, err := tx.Put(key, &Task{\n \t\tCategory: \"Personal\",\n \t\tDone: false,\n \t\tPriority: 4,\n \t\tDescription: \"Learn Cloud Datastore\",\n \t})\n \treturn err\n })\n\n### Java\n\n\nTo learn how to install and use the client library for Datastore mode, see\n[Datastore mode client libraries](/datastore/docs/reference/libraries).\n\n\nFor more information, see the\n[Datastore mode Java API\nreference documentation](https://cloud.google.com/java/docs/reference/google-cloud-datastore/latest/history).\n\n\nTo authenticate to Datastore mode, set up Application Default Credentials.\nFor more information, see\n\n[Set up authentication for a local development environment](/docs/authentication/set-up-adc-local-dev-environment).\n\n Entity task;\n Transaction txn = datastore.newTransaction();\n try {\n task = txn.get(taskKey);\n if (task == null) {\n task = Entity.newBuilder(taskKey).build();\n txn.put(task);\n txn.commit();\n }\n } finally {\n if (txn.isActive()) {\n txn.rollback();\n }\n }\n\n### Node.js\n\n\nTo learn how to install and use the client library for Datastore mode, see\n[Datastore mode client libraries](/datastore/docs/reference/libraries).\n\n\nFor more information, see the\n[Datastore mode Node.js API\nreference documentation](https://cloud.google.com/nodejs/docs/reference/datastore/latest).\n\n\nTo authenticate to Datastore mode, set up Application Default Credentials.\nFor more information, see\n\n[Set up authentication for a local development environment](/docs/authentication/set-up-adc-local-dev-environment).\n\n async function getOrCreate(taskKey, taskData) {\n const taskEntity = {\n key: taskKey,\n data: taskData,\n };\n const transaction = datastore.transaction();\n\n try {\n await transaction.run();\n const [task] = await transaction.get(taskKey);\n if (task) {\n // The task entity already exists.\n await transaction.rollback();\n } else {\n // Create the task entity.\n transaction.save(taskEntity);\n await transaction.commit();\n }\n return taskEntity;\n } catch (err) {\n await transaction.rollback();\n }\n }\n\n### PHP\n\n\nTo learn how to install and use the client library for Datastore mode, see\n[Datastore mode client libraries](/datastore/docs/reference/libraries).\n\n\nFor more information, see the\n[Datastore mode PHP API\nreference documentation](https://googleapis.github.io/google-cloud-php/#/docs/cloud-datastore/latest).\n\n\nTo authenticate to Datastore mode, set up Application Default Credentials.\nFor more information, see\n\n[Set up authentication for a local development environment](/docs/authentication/set-up-adc-local-dev-environment).\n\n $transaction = $datastore-\u003etransaction();\n $entity = $transaction-\u003elookup($task-\u003ekey());\n if ($entity === null) {\n $entity = $transaction-\u003einsert($task);\n $transaction-\u003ecommit();\n }\n\n### Python\n\n\nTo learn how to install and use the client library for Datastore mode, see\n[Datastore mode client libraries](/datastore/docs/reference/libraries).\n\n\nFor more information, see the\n[Datastore mode Python API\nreference documentation](https://cloud.google.com/python/docs/reference/datastore/latest).\n\n\nTo authenticate to Datastore mode, set up Application Default Credentials.\nFor more information, see\n\n[Set up authentication for a local development environment](/docs/authentication/set-up-adc-local-dev-environment).\n\n from google.cloud import https://cloud.google.com/python/docs/reference/datastore/latest/\n\n # For help authenticating your client, visit\n # https://cloud.google.com/docs/authentication/getting-started\n client = https://cloud.google.com/python/docs/reference/datastore/latest/.https://cloud.google.com/python/docs/reference/datastore/latest/google.cloud.datastore.client.Client.html()\n\n import datetime\n\n with client.https://cloud.google.com/python/docs/reference/datastore/latest/google.cloud.datastore.client.Client.html#google_cloud_datastore_client_Client_transaction():\n key = client.https://cloud.google.com/python/docs/reference/datastore/latest/google.cloud.datastore.client.Client.html#google_cloud_datastore_client_Client_key(\n \"Task\", datetime.datetime.now(tz=datetime.timezone.utc).isoformat()\n )\n\n task = client.https://cloud.google.com/python/docs/reference/datastore/latest/google.cloud.datastore.client.Client.html#google_cloud_datastore_client_Client_get(key)\n\n if not task:\n task = https://cloud.google.com/python/docs/reference/datastore/latest/.https://cloud.google.com/python/docs/reference/datastore/latest/google.cloud.datastore.entity.Entity.html(key)\n task.update({\"description\": \"Example task\"})\n client.https://cloud.google.com/python/docs/reference/datastore/latest/google.cloud.datastore.client.Client.html#google_cloud_datastore_client_Client_put(task)\n\n return task\n\n### Ruby\n\n\nTo learn how to install and use the client library for Datastore mode, see\n[Datastore mode client libraries](/datastore/docs/reference/libraries).\n\n\nFor more information, see the\n[Datastore mode Ruby API\nreference documentation](/ruby/docs/reference/google-cloud-datastore/latest).\n\n\nTo authenticate to Datastore mode, set up Application Default Credentials.\nFor more information, see\n\n[Set up authentication for a local development environment](/docs/authentication/set-up-adc-local-dev-environment).\n\n task = nil\n datastore.transaction do |tx|\n task = tx.find task_key\n if task.nil?\n task = datastore.entity task_key do |t|\n t[\"category\"] = \"Personal\"\n t[\"done\"] = false\n t[\"priority\"] = 4\n t[\"description\"] = \"Learn Cloud Datastore\"\n end\n tx.save task\n end\n end\n\nWhat's next\n-----------\n\n\nTo search and filter code samples for other Google Cloud products, see the\n[Google Cloud sample browser](/docs/samples?product=datastore)."]]