44 lines
2.8 KiB
Markdown
44 lines
2.8 KiB
Markdown
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## Fetching data
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After setting up our structs, implementing traits and initializing configuration, we can easily fetch data from remote servers:
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```no_run
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# use activitypub_federation::fetch::object_id::ObjectId;
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# use activitypub_federation::traits::tests::DbUser;
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# use activitypub_federation::config::FederationConfig;
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# let db_connection = activitypub_federation::traits::tests::DbConnection;
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# let _ = actix_rt::System::new();
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# actix_rt::Runtime::new().unwrap().block_on(async {
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let config = FederationConfig::builder()
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.domain("example.com")
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.app_data(db_connection)
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.build()?;
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let user_id = ObjectId::<DbUser>::new("https://mastodon.social/@LemmyDev")?;
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let data = config.to_request_data();
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let user = user_id.dereference(&data).await;
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assert!(user.is_ok());
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# Ok::<(), anyhow::Error>(())
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}).unwrap()
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```
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`dereference` retrieves the object JSON at the given URL, and uses serde to convert it to `Person`. It then calls your method `ApubObject::from_apub` which inserts it in the database and returns a `DbUser` struct. `request_data` contains the federation config as well as a counter of outgoing HTTP requests. If this counter exceeds the configured maximum, further requests are aborted in order to avoid recursive fetching which could allow for a denial of service attack.
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After dereferencing a remote object, it is stored in the local database and can be retrieved using [ObjectId::dereference_local](crate::fetch::object_id::ObjectId::dereference_local) without any network requests. This is important for performance reasons and for searching.
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We can similarly dereference a user over webfinger with the following method. It fetches the webfinger response from `.well-known/webfinger` and then fetches the actor using [ObjectId::dereference](crate::fetch::object_id::ObjectId::dereference) as above.
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```rust
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# use activitypub_federation::traits::tests::DbConnection;
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# use activitypub_federation::config::FederationConfig;
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# use activitypub_federation::fetch::webfinger::webfinger_resolve_actor;
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# use activitypub_federation::traits::tests::DbUser;
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# let db_connection = DbConnection;
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# let _ = actix_rt::System::new();
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# actix_rt::Runtime::new().unwrap().block_on(async {
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# let config = FederationConfig::builder().domain("example.com").app_data(db_connection).build()?;
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# let data = config.to_request_data();
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let user: DbUser = webfinger_resolve_actor("nutomic@lemmy.ml", &data).await?;
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# Ok::<(), anyhow::Error>(())
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# }).unwrap();
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```
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Note that webfinger queries don't contain a leading `@`. It is possible tha there are multiple Activitypub IDs returned for a single webfinger query in case of multiple actors with the same name (for example Lemmy permits group and person with the same name). In this case `webfinger_resolve_actor` automatically loops and returns the first item which can be dereferenced successfully to the given type.
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