Which annotation is used to bind the value of a method parameter to a named HTTP header in a Spring Boot application?
- @RequestHeader
- @HeaderParam
- @HttpHeader
- @HeaderRequest
The @RequestHeader annotation is used to bind the value of a method parameter to a named HTTP header in a Spring Boot application. By specifying the header name as a parameter to this annotation, you can access the value of the corresponding HTTP header. The other options are not valid annotations for binding HTTP headers in Spring Boot.
To externalize configuration properties in Spring Boot, the _____ annotation can be used on a configuration properties class.
- @AutowiredConfig
- @ConfigurationProperties
- @ExternalizedConfig
- @PropertySource
To externalize configuration properties in Spring Boot, the "@ConfigurationProperties" annotation is used on a configuration properties class. This annotation binds properties from the configuration files (such as "application.yml" or ".properties") to fields in the configuration class, allowing easy access to configuration values.
Consider a scenario where you need to validate user input in a Spring Boot application, ensuring that it meets specific business rules that cannot be expressed with standard JSR-303 annotations. How would you implement this?
- Create custom validation constraints by extending the javax.validation.Constraint interface and implementing the validation logic in the isValid method. Then, apply these custom constraints to the fields or methods in your Spring components.
- Embed the custom validation logic directly into the controller methods, bypassing standard validation mechanisms. Handle validation errors within the controller methods and return custom error responses as needed.
- Implement custom validation logic in custom validators by extending org.springframework.validation.Validator interface and then registering these validators with Spring's validation framework. Apply the validators to the model objects or fields requiring custom validation.
- Use AOP (Aspect-Oriented Programming) to intercept method calls and perform custom validation logic before or after the method execution. Implement custom validation logic in separate aspects and apply them to relevant methods using pointcut expressions.
To implement custom validation rules that cannot be expressed with standard JSR-303 annotations, you should create custom validation constraints by extending javax.validation.Constraint and implement the validation logic in the isValid method. Then, apply these custom constraints to your Spring components. This approach aligns with best practices for custom validation in Spring Boot applications.
How is client-side load balancing achieved in a microservices architecture using Spring Cloud?
- By implementing custom load balancing algorithms in each service
- By relying solely on server-side load balancing
- By using Spring Cloud Gateway
- By utilizing Netflix Ribbon for client-side load balancing
In a microservices architecture with Spring Cloud, client-side load balancing is achieved by using Netflix Ribbon. Ribbon is a client-side load balancer that helps services locate and balance requests across multiple instances of a service.
What strategies would you employ to minimize the garbage collection pause times in a high-throughput Spring Boot application?
- Increasing the heap size to accommodate more objects in memory.
- Implementing custom garbage collection algorithms.
- Using the G1 Garbage Collector and tuning its parameters.
- Avoiding the use of multithreading in the application.
Option 3 is correct. To minimize garbage collection pause times in a high-throughput Spring Boot application, you can use the G1 Garbage Collector and tune its parameters. The G1 Garbage Collector is designed to provide low-latency and predictable garbage collection behavior. Increasing heap size (Option 1) may not necessarily reduce pause times. Implementing custom garbage collection algorithms (Option 2) is complex and not typically recommended. Avoiding multithreading (Option 4) is not a practical solution for improving performance.
The _____ in a YAML configuration file in Spring Boot is used to represent a list of values.
- array:
- collection:
- list:
- sequence:
In a YAML configuration file in Spring Boot, a list of values is represented using a sequence, denoted by -. For example, to define a list of values, you would use the format: - value1 - value2 - value3. This format is commonly used for things like specifying multiple profiles or values in a Spring Boot configuration file.
How can you isolate and test database layers in Spring Boot while performing integration tests, ensuring other layers are not loaded?
- Use the @DataJpaTest annotation
- Use the @SpringBootTest annotation
- Use the @WebMvcTest annotation
- Use the @MockBean annotation
To isolate and test the database layer in Spring Boot, you can use the @DataJpaTest annotation. It focuses on the data layer components and doesn't load unnecessary application context, making it suitable for database integration tests. The other options do not specifically isolate the database layer.
What is the primary purpose of using Mockito in unit testing?
- To create mock objects
- To execute SQL queries
- To generate code coverage reports
- To write test cases
Mockito is primarily used to create mock objects, which simulate the behavior of real objects in a controlled way. Mock objects are helpful for isolating the code being tested and verifying interactions between objects.
Can Bean Validation be applied to method parameters in Spring Boot, and if so, how?
- No, Bean Validation can only be applied to class-level fields.
- Yes, by annotating the method parameters with validation annotations like @Valid.
- Yes, by creating a custom validation aspect and applying it to the methods that need validation.
- Yes, by enabling the spring.validation.method property in the application.properties file.
Bean Validation can be applied to method parameters in Spring Boot by annotating the method parameters with validation annotations such as @Valid. This allows you to validate the input parameters of a method and apply validation rules to them.
How can you create a custom query method in a Spring Data JPA repository?
- By defining a method in the repository interface with a name that follows specific conventions.
- By using the @Query annotation to specify the JPQL query.
- By extending the JpaRepository interface and inheriting built-in methods.
- By using the @CustomQuery annotation to define the custom query.
In Spring Data JPA, custom query methods are created by defining a method in the repository interface with a name that follows specific conventions. Spring Data JPA analyzes the method name and generates the appropriate SQL query, making it a powerful and convenient way to create custom queries without writing SQL explicitly. The other options, while valid in certain contexts, do not describe the typical way to create custom query methods in Spring Data JPA.