Mono
Mono is a Project Reactor publisher type representing an asynchronous computation that emits zero or one item.
Spring in Action, Sixth Edition
Mono is Project Reactor's publisher type for asynchronously emitting zero or one element, including no element when parameterized with Void.
- How it is used
- Carries zero-or-one results through Reactor pipelines, WebFlux handlers, WebClient requests, and reactive user lookups.
- How deep it goes
- Explains creation, subscription, transformation, empty results, and framework integration with code; surveys selected operations rather than the full API.
- Examples
- Shows a greeting pipeline, single-taco controller, ingredient HTTP requests, and reactive user lookup.
- What you can do after
- Apply it via Project Reactor and Spring WebFlux to transform and return single-result pipelines, and via WebClient to consume single responses.
Spring Security in Action, Second Edition
Mono is a Reactor type representing an asynchronous computation that emits zero or one item.
- How it is used
- Represents single-value or empty results returned by reactive web endpoints and composed with reactive authentication data.
- How deep it goes
- Defines publisher cardinality and demonstrates map-based composition, while stopping short of detailed scheduling or operator internals.
- Examples
- Uses Mono.just for a greeting and Mono<Authentication> with map for a personalized authenticated response.
- What you can do after
- Build it from scratch in a WebFlux controller and compose emitted values with Reactor operators.
Read how Spring Security in Action, Second Edition explains Mono →
Related concepts
- producerkind of · A producer is an entity or process that creates or supplies values, data, messages, events, or work for another entity to consume.
- ReactiveUserDetailsServiceused by · ReactiveUserDetailsService is a Spring Security interface for asynchronously retrieving user details used in authentication.
- bodyToMono()produced by · bodyToMono() is a WebClient response operation that converts a response body into a Mono of a specified type.
- allproduced by · An all operation returns a Boolean indicating whether every item in a collection satisfies a condition, or is truthy when no condition is specified.
- RSocketused by · RSocket is a binary application protocol that supports reactive interaction patterns including request-response, request-stream, and fire-and-forget communication.
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