1. What does the @SpringBootApplication annotation do internally?
@SpringBootApplication annotation is equivalent to using @Configuration, @EnableAutoConfiguration, and @ComponentScan with their default attributes.
@Configuration :
Indicates that a class declares one or more @Bean methods and may be processed by the Spring container to generate bean definitions and service requests for those beans at runtime, for example:
@Configuration
public class AppConfig {
@Bean
public MyBean myBean() {
// instantiate, configure and return bean ...
}
}
@EnableAutoConfiguration
Spring Boot auto-configuration attempts to automatically configure your Spring application based on the jar dependencies that you have added. For example, if HSQLDB is on your classpath, and you have not manually configured any database connection beans, then Spring Boot auto-configures an in-memory database.
@ComponentScan
Configures component scanning directives for use with @Configuration classes. Provides support parallel with Spring XML's <context:component-scan> element.
Either basePackageClasses() or basePackages() (or its alias value()) may be specified to define specific packages to scan. If specific packages are not defined, scanning will occur from the package of the class that declares this annotation.
2. How to disable a specific auto-configuration class or exclude any package?
//By using "exclude"- in classpath
@EnableAutoConfiguration(exclude={DataSourceAutoConfiguration.class})
//By using "excludeName" - not in classpath
@EnableAutoConfiguration(excludeName={Foo.class})
//By using property file
spring.autoconfigure.exclude=org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration
3. What is Spring Actuator? What are its advantages?
It provides many features, i.e. what beans are created, the mapping in the controller, the CPU usage, etc. Automatically gathering and auditing health and metrics can then be applied to your application.
It provides a very easy way to access the few production-ready REST endpoints and fetch all kinds of information from the web. But by using these endpoints, you can do many things to see here the endpoint docs.
Enabling/disabling the actuator is easy; the simplest way is to enable features to add the dependency (Maven/Gradle) to the spring-boot-starter-actuator, i.e. Starter. If you don't want the actuator to be enabled, then don't add the dependency.
4. What is a shutdown in the actuator?
Shutdown is an endpoint that allows the application to be gracefully shutdown. This feature is not enabled by default. You can enable this by using management.endpoint.shutdown.enabled=true in your application.properties file. But be careful about this if you are using this.
5. Is this possible to change the port of Embedded Tomcat server in Spring boot?
Yes, it's possible to change the port. You can use the application.properties file to change the port. But you need to mention "server.port" (i.e. server.port=8081). Make sure you have application.properties in your project classpath; REST Spring framework will take care of the rest. If you mention server.port=0 , then it will automatically assign any available port.
6. Can we override or replace the Embedded Tomcat server in Spring Boot?
Yes, we can replace the Embedded Tomcat with any other servers by using the Starter dependencies. You can use spring-boot-starter-jetty or spring-boot-starter-undertow as a dependency for each project as you need.
spring-boot-starter-web comes with Embedded Tomcat. We need to exclude this dependency.
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
<exclusions>
<exclusion>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-tomcat</artifactId>
</exclusion>
</exclusions>
</dependency>
Adding Dependencies
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-undertow</artifactId>
</dependency>
7.Can we disable the default web server in the Spring Boot application?
The major strong point in Spring is to provide flexibility to build your application loosely coupled. Spring provides features to disable the web server in a quick configuration. Yes, we can use the application.properties to configure the web application type, i.e. spring.main.web-application-type=none.
8. How does it work? How does it know what to configure?
• Auto-configuration works by analyzing the classpath
The meat of the code is the use of the @ConditionalOnClass annotation
9. How to reload my changes on Spring Boot without having to restart server?
Include following maven dependency in the application.
<dependency>
<groupId>org.springframework</groupId>
<artifactId>springloaded</artifactId>
<version>1.2.6.RELEASE</version>
</dependency>
Automatic restart
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-devtools</artifactId>
<optional>true</optional>
</dependency>
10. How to implement Spring web using Spring boot?
Web Application Convenience
• Boot automatically configures
– A DispatcherServlet & ContextLoaderListener
– Spring MVC using same defaults as @EnableWebMvc
• Plus many useful extra features:
– Static resources served from classpath
• /static, /public, /resources or /META-INF/resources
– Templates served from /templates
• If Velocity, Freemarker, Thymeleaf, or Groovy on classpath
– Provides default /error mapping
• Easily overridden
– Default MessageSource for I18N
11. How to configure datasource using Spring boot?
• Use either spring-boot-starter-jdbc or spring-boot-starterdata-jpa and include a JDBC driver on classpath
• Declare properties
spring.datasource.url=jdbc:mysql://localhost/test
spring.datasource.username=dbuser
spring.datasource.password=dbpass
spring.datasource.driver-class-name=com.mysql.jdbc.Driver
– Spring Boot will create a DataSource with properties set
– Will even use a connection pool if the library is found on the classpath!
12 How do you add Add a Servlet, Filter or Listener to an application?
There are two ways to add Servlet, Filter, ServletContextListener and the other listeners supported by the Servlet spec to your application. You can either provide Spring beans for them or enable scanning for Servlet components.
13. How do you Enable HTTP response compression in spring boot?
HTTP response compression is supported by Jetty, Tomcat, and Undertow. It can be enabled by adding server.compression.enabled=true in application.properties.
14. How to execute Spring Batch jobs on startup?
Spring Batch auto-configuration is enabled by adding @EnableBatchProcessing (from Spring Batch) somewhere in your context. By default, it executes all Jobs in the application context on startup.
15. How do you Create a deployable war file in spring boot?
Step 1: Extend SpringBootServletInitializer and override its configure method.
Step 2: Change packing type to war in pom.xml or in build.gradle.
Step 3: Mark the embedded servlet container dependency as provided.
16. How to write custom log configuration in spring boot?
You can force Spring Boot to use a particular logging system using the org.springframework.boot.logging.LoggingSystem system property. The value should be the fully-qualified class name of a logging system implementation. You can also disable Spring Boot’s logging configuration entirely by using a value of none.
17. What are Profiles in spring boot?
Spring Profiles provide a way to segregate parts of your application configuration and make it only available in certain environments. Any @Component or @Configuration can be marked with @Profile to limit when it is loaded.
18. What is spring-boot-starter-parent?
The spring-boot-starter-parent is a special starter that makes Maven or Gradle dependency-management easier by adding jars to your classpath.
It adds a basic set of spring jars needed for any type of spring based applications.
19. Can you control logging with Spring Boot? How?
Yes, we can control logging with Spring Boot by specifying log levels on application.properties file. Spring Boot loads this file when it exists in the classpath and it can be used to configure both Spring Boot and application code.
Spring Boot uses Commons Logging for all internal logging and you can change log levels by adding following lines in the application.properties file:
logging.level.org.springframework=DEBUG
logging.level.com.demo=INFO
20.
@SpringBootApplication annotation is equivalent to using @Configuration, @EnableAutoConfiguration, and @ComponentScan with their default attributes.
@Configuration :
Indicates that a class declares one or more @Bean methods and may be processed by the Spring container to generate bean definitions and service requests for those beans at runtime, for example:
@Configuration
public class AppConfig {
@Bean
public MyBean myBean() {
// instantiate, configure and return bean ...
}
}
@EnableAutoConfiguration
Spring Boot auto-configuration attempts to automatically configure your Spring application based on the jar dependencies that you have added. For example, if HSQLDB is on your classpath, and you have not manually configured any database connection beans, then Spring Boot auto-configures an in-memory database.
@ComponentScan
Configures component scanning directives for use with @Configuration classes. Provides support parallel with Spring XML's <context:component-scan> element.
Either basePackageClasses() or basePackages() (or its alias value()) may be specified to define specific packages to scan. If specific packages are not defined, scanning will occur from the package of the class that declares this annotation.
2. How to disable a specific auto-configuration class or exclude any package?
//By using "exclude"- in classpath
@EnableAutoConfiguration(exclude={DataSourceAutoConfiguration.class})
//By using "excludeName" - not in classpath
@EnableAutoConfiguration(excludeName={Foo.class})
//By using property file
spring.autoconfigure.exclude=org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration
3. What is Spring Actuator? What are its advantages?
It provides many features, i.e. what beans are created, the mapping in the controller, the CPU usage, etc. Automatically gathering and auditing health and metrics can then be applied to your application.
It provides a very easy way to access the few production-ready REST endpoints and fetch all kinds of information from the web. But by using these endpoints, you can do many things to see here the endpoint docs.
Enabling/disabling the actuator is easy; the simplest way is to enable features to add the dependency (Maven/Gradle) to the spring-boot-starter-actuator, i.e. Starter. If you don't want the actuator to be enabled, then don't add the dependency.
4. What is a shutdown in the actuator?
Shutdown is an endpoint that allows the application to be gracefully shutdown. This feature is not enabled by default. You can enable this by using management.endpoint.shutdown.enabled=true in your application.properties file. But be careful about this if you are using this.
5. Is this possible to change the port of Embedded Tomcat server in Spring boot?
Yes, it's possible to change the port. You can use the application.properties file to change the port. But you need to mention "server.port" (i.e. server.port=8081). Make sure you have application.properties in your project classpath; REST Spring framework will take care of the rest. If you mention server.port=0 , then it will automatically assign any available port.
6. Can we override or replace the Embedded Tomcat server in Spring Boot?
Yes, we can replace the Embedded Tomcat with any other servers by using the Starter dependencies. You can use spring-boot-starter-jetty or spring-boot-starter-undertow as a dependency for each project as you need.
spring-boot-starter-web comes with Embedded Tomcat. We need to exclude this dependency.
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
<exclusions>
<exclusion>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-tomcat</artifactId>
</exclusion>
</exclusions>
</dependency>
Adding Dependencies
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-undertow</artifactId>
</dependency>
7.Can we disable the default web server in the Spring Boot application?
The major strong point in Spring is to provide flexibility to build your application loosely coupled. Spring provides features to disable the web server in a quick configuration. Yes, we can use the application.properties to configure the web application type, i.e. spring.main.web-application-type=none.
8. How does it work? How does it know what to configure?
• Auto-configuration works by analyzing the classpath
The meat of the code is the use of the @ConditionalOnClass annotation
9. How to reload my changes on Spring Boot without having to restart server?
Include following maven dependency in the application.
<dependency>
<groupId>org.springframework</groupId>
<artifactId>springloaded</artifactId>
<version>1.2.6.RELEASE</version>
</dependency>
Automatic restart
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-devtools</artifactId>
<optional>true</optional>
</dependency>
10. How to implement Spring web using Spring boot?
Web Application Convenience
• Boot automatically configures
– A DispatcherServlet & ContextLoaderListener
– Spring MVC using same defaults as @EnableWebMvc
• Plus many useful extra features:
– Static resources served from classpath
• /static, /public, /resources or /META-INF/resources
– Templates served from /templates
• If Velocity, Freemarker, Thymeleaf, or Groovy on classpath
– Provides default /error mapping
• Easily overridden
– Default MessageSource for I18N
11. How to configure datasource using Spring boot?
• Use either spring-boot-starter-jdbc or spring-boot-starterdata-jpa and include a JDBC driver on classpath
• Declare properties
spring.datasource.url=jdbc:mysql://localhost/test
spring.datasource.username=dbuser
spring.datasource.password=dbpass
spring.datasource.driver-class-name=com.mysql.jdbc.Driver
– Spring Boot will create a DataSource with properties set
– Will even use a connection pool if the library is found on the classpath!
12 How do you add Add a Servlet, Filter or Listener to an application?
There are two ways to add Servlet, Filter, ServletContextListener and the other listeners supported by the Servlet spec to your application. You can either provide Spring beans for them or enable scanning for Servlet components.
13. How do you Enable HTTP response compression in spring boot?
HTTP response compression is supported by Jetty, Tomcat, and Undertow. It can be enabled by adding server.compression.enabled=true in application.properties.
14. How to execute Spring Batch jobs on startup?
Spring Batch auto-configuration is enabled by adding @EnableBatchProcessing (from Spring Batch) somewhere in your context. By default, it executes all Jobs in the application context on startup.
15. How do you Create a deployable war file in spring boot?
Step 1: Extend SpringBootServletInitializer and override its configure method.
Step 2: Change packing type to war in pom.xml or in build.gradle.
Step 3: Mark the embedded servlet container dependency as provided.
16. How to write custom log configuration in spring boot?
You can force Spring Boot to use a particular logging system using the org.springframework.boot.logging.LoggingSystem system property. The value should be the fully-qualified class name of a logging system implementation. You can also disable Spring Boot’s logging configuration entirely by using a value of none.
17. What are Profiles in spring boot?
Spring Profiles provide a way to segregate parts of your application configuration and make it only available in certain environments. Any @Component or @Configuration can be marked with @Profile to limit when it is loaded.
18. What is spring-boot-starter-parent?
The spring-boot-starter-parent is a special starter that makes Maven or Gradle dependency-management easier by adding jars to your classpath.
It adds a basic set of spring jars needed for any type of spring based applications.
19. Can you control logging with Spring Boot? How?
Yes, we can control logging with Spring Boot by specifying log levels on application.properties file. Spring Boot loads this file when it exists in the classpath and it can be used to configure both Spring Boot and application code.
Spring Boot uses Commons Logging for all internal logging and you can change log levels by adding following lines in the application.properties file:
logging.level.org.springframework=DEBUG
logging.level.com.demo=INFO
20.
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