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//! Automatic JSON (de)serialization support. //! //! See [`Json`](Json) for details. //! //! # Enabling //! //! This module is only available when the `json` feature is enabled. Enable it //! in `Cargo.toml` as follows: //! //! ```toml //! [dependencies.rocket] //! version = "0.5.0-rc.1" //! features = ["json"] //! ``` //! //! # Testing //! //! The [`LocalRequest`] and [`LocalResponse`] types provide [`json()`] and //! [`into_json()`] methods to create a request with serialized JSON and //! deserialize a response as JSON, respectively. //! //! [`LocalRequest`]: crate::local::blocking::LocalRequest //! [`LocalResponse`]: crate::local::blocking::LocalResponse //! [`json()`]: crate::local::blocking::LocalRequest::json() //! [`into_json()`]: crate::local::blocking::LocalResponse::into_json() use std::io; use std::ops::{Deref, DerefMut}; use crate::request::{Request, local_cache}; use crate::data::{Limits, Data, FromData, Outcome}; use crate::response::{self, Responder, content}; use crate::http::Status; use crate::form::prelude as form; use serde::{Serialize, Deserialize}; #[doc(hidden)] pub use serde_json; /// The JSON guard: easily consume and return JSON. /// /// ## Receiving JSON /// /// `Json` is both a data guard and a form guard. /// /// ### Data Guard /// /// To parse request body data as JSON , add a `data` route argument with a /// target type of `Json<T>`, where `T` is some type you'd like to parse from /// JSON. `T` must implement [`serde::Deserialize`]. /// /// ```rust /// # #[macro_use] extern crate rocket; /// # type User = usize; /// use rocket::serde::json::Json; /// /// #[post("/user", format = "json", data = "<user>")] /// fn new_user(user: Json<User>) { /// /* ... */ /// } /// ``` /// /// You don't _need_ to use `format = "json"`, but it _may_ be what you want. /// Using `format = json` means that any request that doesn't specify /// "application/json" as its `Content-Type` header value will not be routed to /// the handler. /// /// ### Form Guard /// /// `Json<T>`, as a form guard, accepts value and data fields and parses the /// data as a `T`. Simple use `Json<T>`: /// /// ```rust /// # #[macro_use] extern crate rocket; /// # type Metadata = usize; /// use rocket::form::{Form, FromForm}; /// use rocket::serde::json::Json; /// /// #[derive(FromForm)] /// struct User<'r> { /// name: &'r str, /// metadata: Json<Metadata> /// } /// /// #[post("/user", data = "<form>")] /// fn new_user(form: Form<User<'_>>) { /// /* ... */ /// } /// ``` /// /// ### Incoming Data Limits /// /// The default size limit for incoming JSON data is 1MiB. Setting a limit /// protects your application from denial of service (DoS) attacks and from /// resource exhaustion through high memory consumption. The limit can be /// increased by setting the `limits.json` configuration parameter. For /// instance, to increase the JSON limit to 5MiB for all environments, you may /// add the following to your `Rocket.toml`: /// /// ```toml /// [global.limits] /// json = 5242880 /// ``` /// /// ## Sending JSON /// /// If you're responding with JSON data, return a `Json<T>` type, where `T` /// implements [`Serialize`] from [`serde`]. The content type of the response is /// set to `application/json` automatically. /// /// ```rust /// # #[macro_use] extern crate rocket; /// # type User = usize; /// use rocket::serde::json::Json; /// /// #[get("/users/<id>")] /// fn user(id: usize) -> Json<User> { /// let user_from_id = User::from(id); /// /* ... */ /// Json(user_from_id) /// } /// ``` #[derive(Debug)] pub struct Json<T>(pub T); /// Error returned by the [`Json`] guard when JSON deserialization fails. #[derive(Debug)] pub enum Error<'a> { /// An I/O error occurred while reading the incoming request data. Io(io::Error), /// The client's data was received successfully but failed to parse as valid /// JSON or as the requested type. The `&str` value in `.0` is the raw data /// received from the user, while the `Error` in `.1` is the deserialization /// error from `serde`. Parse(&'a str, serde_json::error::Error), } impl<T> Json<T> { /// Consumes the JSON wrapper and returns the wrapped item. /// /// # Example /// ```rust /// # use rocket::serde::json::Json; /// let string = "Hello".to_string(); /// let my_json = Json(string); /// assert_eq!(my_json.into_inner(), "Hello".to_string()); /// ``` #[inline(always)] pub fn into_inner(self) -> T { self.0 } } impl<'r, T: Deserialize<'r>> Json<T> { fn from_str(s: &'r str) -> Result<Self, Error<'r>> { serde_json::from_str(s).map(Json).map_err(|e| Error::Parse(s, e)) } async fn from_data(req: &'r Request<'_>, data: Data<'r>) -> Result<Self, Error<'r>> { let limit = req.limits().get("json").unwrap_or(Limits::JSON); let string = match data.open(limit).into_string().await { Ok(s) if s.is_complete() => s.into_inner(), Ok(_) => { let eof = io::ErrorKind::UnexpectedEof; return Err(Error::Io(io::Error::new(eof, "data limit exceeded"))); }, Err(e) => return Err(Error::Io(e)), }; Self::from_str(local_cache!(req, string)) } } #[crate::async_trait] impl<'r, T: Deserialize<'r>> FromData<'r> for Json<T> { type Error = Error<'r>; async fn from_data(req: &'r Request<'_>, data: Data<'r>) -> Outcome<'r, Self> { match Self::from_data(req, data).await { Ok(value) => Outcome::Success(value), Err(Error::Io(e)) if e.kind() == io::ErrorKind::UnexpectedEof => { Outcome::Failure((Status::PayloadTooLarge, Error::Io(e))) }, Err(Error::Parse(s, e)) if e.classify() == serde_json::error::Category::Data => { Outcome::Failure((Status::UnprocessableEntity, Error::Parse(s, e))) }, Err(e) => Outcome::Failure((Status::BadRequest, e)), } } } /// Serializes the wrapped value into JSON. Returns a response with Content-Type /// JSON and a fixed-size body with the serialized value. If serialization /// fails, an `Err` of `Status::InternalServerError` is returned. impl<'r, T: Serialize> Responder<'r, 'static> for Json<T> { fn respond_to(self, req: &'r Request<'_>) -> response::Result<'static> { let string = serde_json::to_string(&self.0) .map_err(|e| { error_!("JSON failed to serialize: {:?}", e); Status::InternalServerError })?; content::Json(string).respond_to(req) } } impl<T> From<T> for Json<T> { fn from(value: T) -> Self { Json(value) } } impl<T> Deref for Json<T> { type Target = T; #[inline(always)] fn deref(&self) -> &T { &self.0 } } impl<T> DerefMut for Json<T> { #[inline(always)] fn deref_mut(&mut self) -> &mut T { &mut self.0 } } impl From<Error<'_>> for form::Error<'_> { fn from(e: Error<'_>) -> Self { match e { Error::Io(e) => e.into(), Error::Parse(_, e) => form::Error::custom(e) } } } #[crate::async_trait] impl<'v, T: Deserialize<'v> + Send> form::FromFormField<'v> for Json<T> { fn from_value(field: form::ValueField<'v>) -> Result<Self, form::Errors<'v>> { Ok(Self::from_str(field.value)?) } async fn from_data(f: form::DataField<'v, '_>) -> Result<Self, form::Errors<'v>> { Ok(Self::from_data(f.request, f.data).await?) } } /// Serializes the value into JSON. Returns a response with Content-Type JSON /// and a fixed-size body with the serialized value. impl<'r> Responder<'r, 'static> for Value { fn respond_to(self, req: &'r Request<'_>) -> response::Result<'static> { content::Json(self.to_string()).respond_to(req) } } crate::export! { /// A macro to create ad-hoc JSON serializable values using JSON syntax. /// /// The return type of a `json!` invocation is [`Value`](Value). A value /// created with this macro can be returned from a handler as follows: /// /// ```rust /// # #[macro_use] extern crate rocket; /// use rocket::serde::json::{json, Value}; /// /// #[get("/json")] /// fn get_json() -> Value { /// json!({ /// "key": "value", /// "array": [1, 2, 3, 4] /// }) /// } /// ``` /// /// The [`Responder`](crate::response::Responder) implementation for /// `Value` serializes the value into a JSON string and sets it as the body /// of the response with a `Content-Type` of `application/json`. /// /// # Examples /// /// Create a simple JSON object with two keys: `"username"` and `"id"`: /// /// ```rust /// use rocket::serde::json::json; /// /// let value = json!({ /// "username": "mjordan", /// "id": 23 /// }); /// ``` /// /// Create a more complex object with a nested object and array: /// /// ```rust /// # use rocket::serde::json::json; /// let value = json!({ /// "code": 200, /// "success": true, /// "payload": { /// "features": ["serde", "json"], /// "ids": [12, 121], /// }, /// }); /// ``` /// /// Variables or expressions can be interpolated into the JSON literal. Any type /// interpolated into an array element or object value must implement serde's /// `Serialize` trait, while any type interpolated into a object key must /// implement `Into<String>`. /// /// ```rust /// # use rocket::serde::json::json; /// let code = 200; /// let features = vec!["serde", "json"]; /// /// let value = json!({ /// "code": code, /// "success": code == 200, /// "payload": { /// features[0]: features[1] /// } /// }); /// ``` /// /// Trailing commas are allowed inside both arrays and objects. /// /// ```rust /// # use rocket::serde::json::json; /// let value = json!([ /// "notice", /// "the", /// "trailing", /// "comma -->", /// ]); /// ``` macro_rules! json { ($($json:tt)+) => ($crate::serde::json::serde_json::json!($($json)*)); } } /// An arbitrary JSON value as returned by [`json!`]. /// /// # `Responder` /// /// `Value` is a `Responder` that serializes the represented value into a JSON /// string and sets the string as the body of a fixed-sized response with a /// `Content-Type` of `application/json`. /// /// # Usage /// /// A value of this type is returned by [`json!`]. The macro and this type are /// typically used to construct JSON values in an ad-hoc fashion during request /// handling. This looks something like: /// /// ```rust /// # #[macro_use] extern crate rocket; /// use rocket::serde::json::{json, Value}; /// /// #[get("/json")] /// fn get_json() -> Value { /// json!({ /// "id": 83, /// "values": [1, 2, 3, 4] /// }) /// } /// ``` #[doc(inline)] pub use serde_json::Value; /// Deserialize an instance of type `T` from bytes of JSON text. /// /// # Example /// /// ``` /// use rocket::serde::{Deserialize, json}; /// /// #[derive(Debug, PartialEq, Deserialize)] /// #[serde(crate = "rocket::serde")] /// struct Data<'r> { /// framework: &'r str, /// stars: usize, /// } /// /// let bytes = br#" /// { /// "framework": "Rocket", /// "stars": 5 /// } /// "#; /// /// let data: Data = json::from_slice(bytes).unwrap(); /// assert_eq!(data, Data { framework: "Rocket", stars: 5, }); /// ``` /// /// # Errors /// /// This conversion can fail if the structure of the input does not match the /// structure expected by `T`, for example if `T` is a struct type but the input /// contains something other than a JSON map. It can also fail if the structure /// is correct but `T`'s implementation of `Deserialize` decides that something /// is wrong with the data, for example required struct fields are missing from /// the JSON map or some number is too big to fit in the expected primitive /// type. #[inline(always)] pub fn from_slice<'a, T>(v: &'a [u8]) -> Result<T, serde_json::error::Error> where T: Deserialize<'a>, { serde_json::from_slice(v) } /// Deserialize an instance of type `T` from a string of JSON text. /// /// # Example /// /// ``` /// use rocket::serde::{Deserialize, json}; /// /// #[derive(Debug, PartialEq, Deserialize)] /// #[serde(crate = "rocket::serde")] /// struct Data<'r> { /// framework: &'r str, /// stars: usize, /// } /// /// let string = r#" /// { /// "framework": "Rocket", /// "stars": 5 /// } /// "#; /// /// let data: Data = json::from_str(string).unwrap(); /// assert_eq!(data, Data { framework: "Rocket", stars: 5, }); /// ``` /// /// # Errors /// /// This conversion can fail if the structure of the input does not match the /// structure expected by `T`, for example if `T` is a struct type but the input /// contains something other than a JSON map. It can also fail if the structure /// is correct but `T`'s implementation of `Deserialize` decides that something /// is wrong with the data, for example required struct fields are missing from /// the JSON map or some number is too big to fit in the expected primitive /// type. #[inline(always)] pub fn from_str<'a, T>(v: &'a str) -> Result<T, serde_json::error::Error> where T: Deserialize<'a>, { serde_json::from_str(v) } /// Interpret a [`Value`] as an instance of type `T`. /// /// # Example /// /// ``` /// use rocket::serde::{Deserialize, json}; /// /// #[derive(Debug, PartialEq, Deserialize)] /// #[serde(crate = "rocket::serde")] /// struct Data { /// framework: String , /// stars: usize, /// } /// /// let value = json::json!({ /// "framework": "Rocket", /// "stars": 5 /// }); /// /// let data: Data = json::from_value(value).unwrap(); /// assert_eq!(data, Data { framework: "Rocket".into(), stars: 5, }); /// ``` /// /// # Errors /// /// This conversion can fail if the structure of the input does not match the /// structure expected by `T`, for example if `T` is a struct type but the input /// contains something other than a JSON map. It can also fail if the structure /// is correct but `T`'s implementation of `Deserialize` decides that something /// is wrong with the data, for example required struct fields are missing from /// the JSON map or some number is too big to fit in the expected primitive /// type. #[inline(always)] pub fn from_value<T>(v: Value) -> Result<T, serde_json::error::Error> where T: crate::serde::DeserializeOwned { serde_json::from_value(v) }