In Spring Boot reactive programming, the map method is used to transform the items emitted by a Publisher. The map operation allows you to apply a function to each item emitted by a Publisher and produce a new Publisher with the transformed items. This is a common operation when working with reactive streams to perform data transformations.

In Spring Boot, the properties defined in the application.yml file are used to configure the application. While you can also use application.properties, YAML configuration files are a popular choice due to their readability and ease of use for defining properties.

In Spring Boot, the spring.cache.cache-type property is used to configure the cache storage type. This property allows you to specify whether you want to use an in-memory cache, an external cache, or another type of cache storage for your application's caching needs. Configuring the cache type is essential for optimizing performance and resource usage.

In Spring Boot, the @RequestBody annotation is used to deserialize the HTTP request body into a Java object. This is particularly useful when dealing with POST or PUT requests where data is sent in the request body. The other annotations are used for different purposes, such as specifying response bodies, request parameters, or path variables.

To conditionally process a configuration class based on the presence of a certain bean, you can use the @ConditionalOnBean annotation. This annotation ensures that the configuration class is only processed if the specified bean is present in the ApplicationContext. It's a powerful way to control the activation of configuration based on runtime conditions.

In Spring Boot, you can conditionally enable caching by using the @ConditionalOnProperty annotation with the property name as "spring.cache.enabled." This annotation allows caching to be enabled only when the specified property is set to true. The other annotations do not provide conditional caching based on a property.

Spring Boot provides the MockMvc class, which allows you to simulate HTTP requests and responses for testing controller methods without the need to start a server. It's a crucial tool for integration testing in Spring Boot.

The correct annotation to handle exceptions globally across the entire Spring Boot application is @ControllerAdvice. This annotation allows you to define global exception handlers that can be applied to multiple controllers. It's a powerful tool for managing exceptions consistently throughout your application. The other options are not used for this purpose.

The primary role of the UserDetailsService in Spring Security is to load user details (including username, password, and roles) from a data store, typically a database. It's a fundamental component used for authentication and authorization, as it provides the necessary user information for the security framework to make access control decisions. The other options describe tasks related to authentication and authorization but are not the primary role of UserDetailsService.

The primary responsibility of an OAuth2 Authorization Server in a Spring Boot application is to authenticate users and grant access tokens to authorized clients. It does not store user passwords but rather validates user credentials and authorizes access to protected resources. It also does not manage user profiles and preferences, nor does it control database access; these are typically the tasks of the application's authentication system and database itself.