To optimize the performance of RESTful APIs in Spring Boot, developers can enable GZIP compression for the HTTP response. Enabling GZIP compression reduces the amount of data sent over the network by compressing the response before sending it to the client. This reduces the bandwidth usage and speeds up API response times, especially when dealing with large payloads. Enabling GZIP compression is a common technique for improving the performance of web applications, including RESTful APIs.

In a Spring Cloud environment, to configure a service to discover its peers using Eureka, the property eureka.client.register-with-eureka must be defined in the application's properties or YAML file. This property determines whether the service should register itself with the Eureka server. Setting it to true allows the service to register, and it will be discoverable by other services through Eureka.

Mockito is a popular framework used for mocking objects in unit tests in Spring Boot applications. It allows you to create mock objects and define their behavior during testing.

In unit testing of Spring Boot applications, the assertTrue method of the Assert class is commonly used to check if the specified condition is true. This is helpful for verifying that a certain condition or assertion holds true during the test.

The primary Spring Cloud component used for service discovery in a microservices architecture is Eureka. Eureka is a server-based service registry that allows microservices to register themselves and discover other services in the system.

When testing service layer components in Spring Boot, you can use the @MockBean annotation to mock dependencies and avoid loading the complete ApplicationContext. This helps in isolating the unit under test.

The purpose of password encoding in Spring Security is to prevent password exposure. Storing passwords in plaintext is a security risk, so Spring Security encourages password encoding (hashing) to store passwords securely. This way, even if the password database is compromised, attackers cannot easily retrieve the original passwords. Password encoding is not meant to obfuscate passwords but to securely store them and prevent unauthorized access to plaintext passwords.

Transaction management in Spring Data JPA requires manual configuration. Spring Data JPA doesn't automatically manage transactions. Developers typically use the @Transactional annotation or XML-based configuration to specify transaction boundaries for methods in their repositories. The other options are not accurate; Spring Data JPA can handle both read and write transactions, and it does not require manual configuration for all repositories.

In a Spring Boot application, the @Cacheable annotation is primarily used to mark a method as cacheable. When this annotation is applied to a method, the results of that method are cached, and subsequent calls with the same parameters will retrieve the cached result instead of executing the method again. The other annotations may be used for cache-related operations, but @Cacheable is specifically for marking cacheable methods.

In OAuth2, the /token endpoint is used by the client to obtain an access token. The client exchanges its credentials or authorization code for an access token at this endpoint, allowing it to access protected resources on behalf of the user.