Crate juniper[][src]

Expand description


GraphQL is a data query language developed by Facebook intended to serve mobile and web application frontends.

Juniper makes it possible to write GraphQL servers in Rust that are type-safe and blazingly fast. We also try to make declaring and resolving GraphQL schemas as convenient as possible as Rust will allow.

Juniper does not include a web server - instead it provides building blocks to make integration with existing servers straightforward. It optionally provides a pre-built integration for the Iron and Rocket frameworks, including embedded Graphiql for easy debugging.

Getting Started

The best place to get started is the Juniper Book, which contains guides with plenty of examples, covering all features of Juniper.

To get started quickly and get a feel for Juniper, check out the Quickstart section.

For specific information about macros, types and the Juniper api, the API Reference is the best place to look.

You can also check out src/tests/ to see a complex schema including polymorphism with traits and interfaces. For an example of web framework integration, see the rocket and iron examples folders.


Juniper supports the full GraphQL query language according to the specification, including interfaces, unions, schema introspection, and validations. It does not, however, support the schema language.

As an exception to other GraphQL libraries for other languages, Juniper builds non-null types by default. A field of type Vec<Episode> will be converted into [Episode!]!. The corresponding Rust type for e.g. [Episode] would be Option<Vec<Option<Episode>>>.


Data types

Juniper has automatic integration with some very common Rust crates to make building schemas a breeze. The types from these crates will be usable in your Schemas automatically.

Web Frameworks

API Stability

Juniper has not reached 1.0 yet, thus some API instability should be expected.


pub use crate::executor::Context;
pub use crate::executor::ExecutionError;
pub use crate::executor::ExecutionResult;
pub use crate::executor::Executor;
pub use crate::executor::FieldError;
pub use crate::executor::FieldResult;
pub use crate::executor::FromContext;
pub use crate::executor::IntoFieldError;
pub use crate::executor::IntoResolvable;
pub use crate::executor::Registry;
pub use crate::executor::ValuesStream;
pub use crate::executor::Variables;


Resolve the document to values

Utilities for building HTTP endpoints in a library-agnostic manner

Provides GraphQLType implementations for some external types

Marker traits for GraphQL types.

Types used to describe a GraphQL schema

Query parser and language utilities

Query validation related methods and data structures


Construct JSON-like values by using JSON syntax


Field argument container

Utility type to define read-only schemas

Utillity type to define read-only schemas

Represents the result of executing a GraphQL operation (after parsing and validating has been done).

An ID as defined by the GraphQL specification

An argument passed into the query

A selection performed by a query

A Object value

Executor owning all its variables. Can be used after Executor was destroyed.

Root query node of a schema

Query validation error

Metadata for a schema

Data structure used to wrap items with start and end markers in the input source


An enum that describes if a field is available in all types of the interface or only in a certain subtype

The default scalar value representation in juniper

An error that prevented query execution

A JSON-like value that can be passed into the query execution, either out-of-band, or in-band as default variable values. These are not constant and might contain variables.

A JSON-like value that can is used as argument in the query execution

Nullable can be used in situations where you need to distinguish between an implicitly and explicitly null input value.

Error while parsing a GraphQL query

Entry in a GraphQL selection set

A type literal in the syntax tree

GraphQL type kind

Serializable value returned from query and field execution.


Conversion of a GraphQLValue to its trait object.

This trait is used in juniper::graphql_subscription macro to get stream’s item type that implements GraphQLValue from type alias provided by user.

Parse an unstructured input value into a Rust data type.

Maker trait for GraphQL interfaces.

Extension of GraphQLType trait with asynchronous subscription execution logic.

Extension of GraphQLValue trait with asynchronous subscription execution logic. It should be used with GraphQLValue in order to implement subscription resolvers on GraphQL objects.

Primary trait used to expose Rust types in a GraphQL schema.

Extension of GraphQLType trait with asynchronous queries/mutations resolvers.

Maker trait for GraphQL unions.

Primary trait used to resolve GraphQL values.

Extension of GraphQLValue trait with asynchronous queries/mutations resolvers.

Trait for wrapping [Stream] into Ok if it’s not Result.

Set of common methods for ConcreteLookAheadSelection and LookAheadSelection.

A trait used to convert a ScalarToken into a certain scalar value type

A trait marking a type that could be used as internal representation of scalar values in juniper

Single subscription connection.

Global subscription coordinator trait.

Losslessly clones a Rust data type into an InputValue.


Execute a query in a provided schema

Execute a query synchronously in a provided schema

Execute the reference introspection query in the provided schema

Resolve subscription into ValuesStream

Type Definitions

An owned dynamically typed Future for use in cases where you can’t statically type your result or need to add some indirection.

Helper alias for naming trait objects of GraphQLValue.

Helper alias for naming trait objects of GraphQLValueAsync.

BoxFuture, but without the Send requirement.

The result of converting a string into a scalar value

Attribute Macros

#[graphql_interface] macro for generating a GraphQL interface implementation for traits and its implementers.

The object proc macro is the primary way of defining GraphQL resolvers that can not be implemented with the GraphQLObject derive.

Expose GraphQL scalars

A proc macro for defining a GraphQL subscription.

#[graphql_union] macro for deriving a GraphQL union implementation for traits.

Derive Macros

This custom derive macro implements the #[derive(GraphQLScalarValue)] derive.

#[derive(GraphQLUnion)] macro for deriving a GraphQL union implementation for enums and structs.