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A circuit breaker is a design pattern used to prevent cascading failures in a microservices architecture. It monitors the status of remote services, and if a service fails repeatedly, the circuit breaker “trips,” temporarily preventing requests to that service, thus maintaining system stability.

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Spring Boot applications can be easily containerized using technologies like Docker. Docker containers can then be deployed on container orchestration platforms like Kubernetes for efficient scaling and management of microservices.

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Spring Boot allows you to externalize configuration using properties or YAML files. You can specify configuration values in these files and have them automatically loaded into your application.

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Microservices in Spring Boot refer to a architectural style for designing and developing software applications as a collection of small, loosely coupled, independently deployable and manageable services. Spring Boot is a popular framework in the Java ecosystem that facilitates the creation of standalone, production-grade Spring-based applications with minimal configuration.

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Microservices Architecture is a software development approach where an application is built as a collection of small, independent, and loosely coupled services that communicate with each other through well-defined APIs (Application Programming Interfaces). In this architectural style, the application is broken down into multiple smaller services, each responsible for a specific business capability or function.

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Following are the major features of Spring Cloud:

• Distributed configuration
• Distributed messaging
• service-to-service calls
• Circuit breakers
• Global locks
• Service registration
• Service Discovery
• Load balancing
• Cluster state
• Routing

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To override the default properties of a Spring Boot project, you can follow these steps:

• Create a Configuration File: In your Spring Boot project, you can create a properties file or a YAML file to override the default properties. By default, Spring Boot looks for a file named properties or application.yml on the classpath.
• Specify Property Overrides: In the created configuration file, you can specify the properties you want to override. You should use the same property names that are defined in the Spring Boot’s default properties.
• Place the Configuration File: Put the configuration file in a location where it will be picked up by Spring Boot. Typically, placing the file in the src/main/resources directory of your project is a good practice.
• Application Restart: If the application is already running, you might need to restart it for the changes to take effect. Spring Boot will automatically read the properties from your configuration file and apply the overrides.

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Implementing Spring Security in a Spring Boot application involves securing your application’s endpoints and resources. Here’s a general step-by-step guide to help you get started:

1. Add Dependencies: In your Spring Boot project’s xml (if using Maven) or build.gradle (if using Gradle), add the necessary dependencies for Spring Security. The most common dependencies are spring-boot-starter-security and spring-boot-starter-web.
2. Configure Security: Create a Java class that extends WebSecurityConfigurerAdapter. This class will define the security configurations for your application. You can override methods to customize authentication, authorization, and other security-related settings.
3. User Authentication: Configure how users are authenticated. You can use in-memory authentication, JDBC-based authentication, or custom authentication providers.
4. Password Encoding: For security reasons, it’s important to store passwords securely. Spring Security provides password encoding mechanisms. Configure password encoding in your SecurityConfig
5. Define Roles and Permissions: You can define roles and permissions to control access to different parts of your application. You can use annotations like @PreAuthorize and @Secured on your controller methods to specify access rules.
6. Customize Login and Logout: Customize the login and logout process by creating appropriate endpoints and pages. You can also customize the login form, success, and failure handlers.
7. Secure Resources: Secure your application’s resources by configuring URL patterns and access rules in your SecurityConfig.
8. Testing Security: Write unit and integration tests to verify the behavior of your security configuration. Spring Security provides testing utilities to help with this.
9. Run and Test: Run your Spring Boot application and test the security features. Try accessing different endpoints with different user roles to ensure the access control is working as expected.

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Spring Boot supports Jetty, Tomcat (default), and undertow servers.

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In Spring Boot, the @WebMvcTest annotation is used to perform unit testing for Spring MVC controllers. This annotation focuses on testing the web layer of your application by setting up the necessary Spring configuration and only loading the relevant components needed for testing the controllers. It helps you isolate the controller layer and its interactions with the Spring MVC infrastructure.

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Configuring logging in a Spring Boot application is a crucial task to monitor and troubleshoot your application effectively. Spring Boot uses the popular logging framework, Logback, by default. Here’s how you can configure Spring Boot application logging:

1. Dependencies: Make sure you have the necessary dependencies in your xml or build.gradle file. Spring Boot’s starter dependency already includes the required logging libraries. If you want to use a different logging framework, you can exclude the default logging dependency and include your preferred one.
2. Properties Configuration: You can configure logging properties in your properties or application.yml file.
3. Logback XML Configuration: For more advanced logging configuration, you can create a logback-spring.xml file in the src/main/resources This XML configuration allows you to define various appenders, loggers, and log levels in a more flexible manner. Refer to the Logback documentation for detailed configuration options.
4. Profiles: Spring Boot allows you to define different logging configurations based on profiles. For example, you can have different log levels for development and production environments by creating separate application-dev.properties and application-prod.properties
5. External Logging Systems: If you want to use external logging systems like Elasticsearch, Splunk, or Logstash, you can integrate them using appropriate libraries or configurations.

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Java 8 is the minimum version required is the minimum for Spring Boot.

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Thymeleaf is a Java-based template engine used for server-side rendering in web applications. It’s commonly used in conjunction with Spring Framework to create dynamic web pages. Thymeleaf allows you to integrate your HTML templates with server-side data, enabling you to dynamically generate content and customize the presentation of your web pages.

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Using Spring Boot for command-line applications can provide you with a robust and organized framework for building command-line tools. Here’s how you can effectively use Spring Boot for developing command-line applications:

1. Project Setup: Start by creating a new Spring Boot project using tools like Spring Initializr or your preferred integrated development environment (IDE).
2. Dependency Configuration: In your xml (if using Maven) or build.gradle (if using Gradle), include the necessary Spring Boot dependencies.
3. Command-Line Runner: Spring Boot provides an interface called CommandLineRunner that you can implement t to run code on application startup. This is a great place to put your command-line logic.
4. Argument Parsing: You can access the command-line arguments passed to your application through the args parameter in the run method of your CommandLineRunner. Spring Boot automatically populates this array with the arguments.
5. Dependency Injection: Spring Boot supports dependency injection, so you can use it to inject services or components into your command-line application. This can help you keep your code modular and well-structured.
6. Configuration: You can use Spring Boot’s configuration mechanisms to manage configuration properties for your command-line application. This could include properties like file paths, connection details, etc.

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To change the default port in a Spring Boot application, follow these steps:

1. Open application.properties or application.yml: In your Spring Boot project, locate the properties or application.yml file.
2. Change the Port Property: In the properties file, add or modify the line to set the desired port.
3. Save the File: Save the changes you’ve made to the properties or application.yml file.
4. Run the Application: When you run your Spring Boot application, it will now start on the port you’ve specified.

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Handling file uploads in Spring Boot applications is a common task that can be accomplished using the Spring Web module.

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In Spring Boot, an embedded container refers to a lightweight web server that is included within the application itself. Spring Boot provides built-in support for embedding servlet containers like Tomcat, Jetty, and Undertow. This allows you to package your application as a self-contained executable JAR (Java Archive) or WAR (Web Archive) file, which contains both your application code and the necessary server components.

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Spring Security is a powerful and widely used framework in the Java ecosystem that focuses on providing security features for Spring-based applications. Its main role is to facilitate the implementation of security measures in your applications, ensuring that they are well-protected against unauthorized access, data breaches, and other security vulnerabilities.

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The @SpringBootApplication annotation is a central component in the Spring Framework for building Java-based enterprise applications. It’s typically used in the main class of a Spring Boot application to indicate that the class is the entry point for the application and to enable various Spring Boot features.

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The @Autowired annotation is a feature in the Spring Framework, which is a popular Java-based framework used for building enterprise applications. The @Autowired annotation is used to automatically inject (or wire) dependencies into a Spring bean.