Top Five Saltation Kick Annotations Alongside Examples For Coffee Developers

Annotations convey completely changed the agency yous write Java code. It's forthwith impossible to write whatever Java code without using annotations but that's for good. They render a lot of value together with that's why it's of import for a Java developer to acquire familiar alongside essential annotations of the framework he or she is using. When I intend close Java, around of the essential annotations which come upward inwards our heed is @Override, @SuppressWarning together with @Deprecated. Similarly, if yous are using Spring Boot framework, an extension of Spring framework which aims to simplify the Java evolution alongside Spring, yous volition oft halt of using a yoke of annotations similar @SpringBootApplication or @EnableAutoConfiguration.

Many Java developer but blindly uses annotations without knowing that what they are together with what they do. They but copy-paste the code without giving much thought.

For example, the @SpringBootApplication annotation is required to most of the primary shape yous write alongside Spring Boot, hence, most of the Java developer halt upward but copy-pasting whole shape together with they trying to customize it for their ain need.

Well, zero is bad, every bit long every bit yous know what yous are doing but but learning a flake of telephone commutation never hurt. Even small-scale information that what does the especially annotation do together with when to utilisation them volition move past times a long agency inwards improving your agreement of the code yous write or read.

In social club to span this gap, I am going to percentage around of the essential Spring Boot annotations every Java developer should live familiar with. I'll but render a quick overview alongside an instance for the sake to move past times along this article curt but yous join Learn Spring Boot inwards 100 Steps to larn them inwards depth alongside to a greater extent than real-world examples.

Spring Boot Annotations Java Developer should know

Without wasting whatever to a greater extent than of your time, hither is my listing of around of the useful Spring Boot annotations which every Java developer using Spring Boot should live familiar with.

1.@SpringBootApplication

This is the most mutual Spring Boot annotations together with yous volition honor it in all likelihood inwards every unmarried Spring Boot application. Since Spring Boot allows yous to execute your Web application without deploying into whatever spider web server similar Tomcat.

You tin run them but similar yous tin run the primary shape inwards Java, this annotation is used to annotate the primary shape of your Spring Boot application. It also enables the auto-configuration characteristic of Spring Boot.

Here is an instance of using the @SpringBootApplication inwards Java:

package boot; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RestController;   @SpringBootApplication public class SpringBootDemo {  public static void main(String args[]) {   SpringApplication.run(SpringBootDemo.class, args); }  }  @RestController class HelloControler{   @RequestMapping("/") public String hello(){   return "Hello Spring Booot"; }  }

This is the simplest instance of RESTful spider web service yous tin write using Spring together with Java. You tin run this similar whatever Java application past times right-clicking on the source file together with "Run every bit Java application" inwards Eclipse. After that, the embedded Tomcat server volition start together with deploy this RESTful spider web service.

When yous volition hitting the URL http://localhost:8080/ (the default port for embedded tomcat server within Spring boot) yous volition live greeted alongside "Hello Spring Boot".

Now, coming dorsum to the @SpringBootApplication annotation, it's genuinely a combination of 3 annotations - @Configuration, @ComponentScan, together with @EnableAutoConfiguration.

If yous know the @Configuration enables Java-based configuration together with the shape annotated alongside @Configuration tin live used to define Spring Beans.

The @ComponentScan enables element scanning so that controller or whatever other element shape yous create volition live automatically discovered together with registered alongside Spring Bean.

And, finally, the @EnableAutoConfiguration enables the auto-configuration characteristic of Spring Boot which tin automatically configure sure as shooting Spring features based upon JAR available inwards Classpath. For example, if H2.jar is introduce inwards the classpath, it tin configure the H2 in-memory database within the Spring application context.

As explained past times Dan Vega on his Spring Boot MasterClass, Spring Boot makes to a greater extent than than 200+ determination to gratis yous from mutual configuration task. If yous desire to customize those decisions yous tin do so.

Btw, the @SpringBootApplication annotation is entirely available shape Spring Boot version 1.1, It wasn't business office of Spring Boot's offset disclose together with afterward added because they realize that almost all the applications were annotated alongside those 3 annotations (@Configuration + @ComponentScan, together with @EnableAutoConfiguration).

2.@EnableAutoConfiguration

This is the master copy Spring Boot annotation which was added to enable the auto-configuration, the flagship Spring kick characteristic which frees developers from mutual configuration task.

The auto-configuration characteristic automatically configures things if sure as shooting classes are introduce inwards the Classpath e.g. if thymeleaf.jar is introduce inwards the Classpath so it tin automatically configure Thymeleaf TemplateResolver together with ViewResolver.

If yous are non using @SpringBootApplication or running on Spring kick version lower than 1.1 so yous tin utilisation @EnableAutoConfiguration annotates to enable the auto-configuration characteristic of Spring Boot.


Another affair which is worth knowing close @EnableAutoConfiguration is that it allows yous to selectively ignore sure as shooting classes from auto-configuration using exclude attribute every bit shown below:

@Configuration @EnableAutoConfiguration(exclude={DataSourceAutoConfiguration.class}) public class SpringBootDemo {   //.. Java code }

If the shape is non on the classpath, yous tin utilisation the excludeName attribute of the @EnableAutoConfiguration annotation together with specify the fully qualified shape name, every bit explained past times Ranga Karnan on  Learn Spring Boot inwards 100 Steps course. One of the best course of pedagogy for beginners to larn Spring boot.

Btw, this Spring Boot annotation is genuinely useful for experienced Spring Boot programmers who intend that Spring kick is also opinionated together with desire to convey around command over the auto-configuration feature.

3.@ContextConfiguration

This annotation specifies how to charge the application context land writing a unit of measurement essay for the Spring environment. Here is an instance of using @ContextConfiguration along alongside @RunWith annotation of JUnit to essay a Service shape inwards Spring Boot.

@RunWith(SpringJUnit4ClassRunner.class) @ContextConfiguration(classes=PaymentConfiguration.class) public class PaymentServiceTests{  @Autowired private PaymentService paymentService;  @Test public void testPaymentService(){    // code to essay PaymentService class  }  }

In this example, @ContextConfiguration shape instructs to charge the Spring application context defined inwards the PaymentConfiguration class.

Btw, fifty-fifty though it does a bang-up undertaking of loading Spring application context, it doesn't render total Spring kick treatment.

As explained past times Craig Walls inwards Spring Boot inwards Action, the Spring Boot applications are ultimately loaded past times SpringBootApplicaiton either explicitly or using the SpringBootServletInitializer.

This non entirely leads beans inwards Spring application context but also enables logging together with loading of properties from external belongings file like applicaiton.properties every bit good every bit other Spring Boot features. But, don't worry, at that spot is around other annotation which provides all of this together with yous tin utilisation that to write a unit of measurement essay alongside Spring kick treatment.

4.@SpringApplicationConfiguration

This is the annotation which addresses shortcomings of @ContextConfiguration annotation discussed inwards the previous section. It provides total Spring Boot handling to your essay classes e.g. it non entirely charge the beans inwards Spring application context but also enable logging together with loads properties from application.properties file.

Btw, yous should ever utilisation @SpringApplicaitonConfiguration instead of @ContextConfigruation for writing unit of measurement essay inwards Spring boot.

Here is an instance of using @SpringApplicatoinConfiguration annotation inwards Spring boot:

@RunWith(SpringJUnit4ClassRunner.class) @SpringApplicationConfiguration(classes=PaymentConfiguration.class) public class PaymentServiceTests{   ...  }

This is the same instance nosotros convey seen inwards the lastly department but re-written using the @SpringApplicationConfiguration annotation this time. Again, I advise yous cheque out the Spring Boot inwards Action majority to larn to a greater extent than close it, ane of the best books to larn Spring Boot framework.

5.@ConditionalOnBean

Spring Boot defines several conditional annotations for auto-configuration like @ConditionalOnBean which tin live used to apply a configuration if the specified edible bean has been configured.


5.1 @ConditionalOnMissingBean
Similarly, yous convey @ConditionalOnMissingBean, which enables the configuration if the specified edible bean has non already been configured.

@ConditionalOnClass
The configuration is applied if the specified shape is available on the Classpath.


5.2 @ConditioanlOnMissingClass
This is the counterpart of the previous annotation. This configuration is applied if the specified shape is non introduce on the Classpath.


5.3 @ConditionalOnExpression
The Configuration is applied if the given Spring Expression Language (SpEL) aspect evaluates to true.


5.4 @ConditionalOnJava
The Configuration is applied if the version of Java matches a specific value or make of versions.

Apart from these conditional annotations listed here, at that spot are to a greater extent than e.g. @ConditioalOnJndi, @ConditioanlOnProperty, @ConditioanlOnResource, @ConditionalOnWebApplication, together with @ConditionalOnNotWebApplication which plant depending upon the presence together with absence of around conditions.

If yous are interested to larn to a greater extent than close them, I advise to move past times through Spring Framework 5: Beginner to Guru, ane of the best course of pedagogy to larn Conditionals together with Spring Boot annotations.

That's all close around of the essential Spring Boot annotations every Java developer should know. If yous are using Spring Boot for creating Spring-based Java spider web application so yous volition come upward across these annotations every forthwith together with then. Just knowing what they do together with where yous tin utilisation volition make yous confidence land reading together with writing Spring kick code.

Further Learning
Learn Spring Boot
Master Java Web Services alongside Spring Boot
Master Hibernate together with JPA alongside Spring Boot inwards 100 Steps


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Thanks for reading this article so far. If yous honor these Spring Boot annotations useful so delight percentage alongside your friends together with colleagues. If yous convey whatever questions or feedback so delight drib a note.

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