Top Five Saltation Kicking Annotations Amongst Examples For Coffee Developers

Annotations bring completely changed the means y'all write Java code. It's straightaway impossible to write whatever Java code without using annotations but that's for good. They render a lot of value in addition to that's why it's of import for a Java developer to acquire familiar amongst essential annotations of the framework he or she is using. When I intend virtually Java, to a greater extent than or less of the essential annotations which come upward inwards our heed is @Override, @SuppressWarning in addition to @Deprecated. Similarly, if y'all are using Spring Boot framework, an extension of Spring framework which aims to simplify the Java evolution amongst Spring, y'all volition oftentimes cease of using a distich of annotations similar @SpringBootApplication or @EnableAutoConfiguration.

Many Java developer simply blindly uses annotations without knowing that what they are in addition to what they do. They simply copy-paste the code without giving much thought.

For example, the @SpringBootApplication annotation is required to most of the principal flat y'all write amongst Spring Boot, hence, most of the Java developer cease upward simply copy-pasting whole flat in addition to they trying to customize it for their ain need.

Well, null is bad, equally long equally y'all know what y'all are doing but simply learning a chip of key never hurt. Even pocket-size information that what does the especially annotation do in addition to when to exercise them volition acquire out a long means inwards improving your agreement of the code y'all write or read.

In club to span this gap, I am going to portion to a greater extent than or less of the essential Spring Boot annotations every Java developer should last familiar with. I'll simply render a quick overview amongst an instance for the sake to acquire out on this article brusk but y'all join Learn Spring Boot inwards 100 Steps to larn them inwards depth amongst 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 to a greater extent than or less of the useful Spring Boot annotations which every Java developer using Spring Boot should last familiar with.

1.@SpringBootApplication

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

You tin laissez passer on the axe run them simply similar y'all tin laissez passer on the axe run the principal flat inwards Java, this annotation is used to annotate the principal flat 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 y'all tin laissez passer on the axe write using Spring in addition to Java. You tin laissez passer on the axe run this similar whatever Java application past times right-clicking on the source file in addition to "Run equally Java application" inwards Eclipse. After that, the embedded Tomcat server volition start in addition to deploy this RESTful spider web service.

When y'all volition striking the URL http://localhost:8080/ (the default port for embedded tomcat server within Spring boot) y'all volition last greeted amongst "Hello Spring Boot".

Now, coming dorsum to the @SpringBootApplication annotation, it's genuinely a combination of iii annotations - @Configuration, @ComponentScan, in addition to @EnableAutoConfiguration.

If y'all know the @Configuration enables Java-based configuration in addition to the flat annotated amongst @Configuration tin laissez passer on the axe last used to define Spring Beans.

The @ComponentScan enables element scanning so that controller or whatever other element flat y'all create volition last automatically discovered in addition to registered amongst Spring Bean.

And, finally, the @EnableAutoConfiguration enables the auto-configuration characteristic of Spring Boot which tin laissez passer on the axe automatically configure surely Spring features based upon JAR available inwards Classpath. For example, if H2.jar is acquaint inwards the classpath, it tin laissez passer on the axe 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+ conclusion to gratis y'all from mutual configuration task. If y'all desire to customize those decisions y'all tin laissez passer on the axe do so.

Btw, the @SpringBootApplication annotation is entirely available shape Spring Boot version 1.1, It wasn't purpose of Spring Boot's outset expose in addition to after added because they realize that almost all the applications were annotated amongst those iii annotations (@Configuration + @ComponentScan, in addition to @EnableAutoConfiguration).

2.@EnableAutoConfiguration

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

The auto-configuration characteristic automatically configures things if surely classes are acquaint inwards the Classpath e.g. if thymeleaf.jar is acquaint inwards the Classpath so it tin laissez passer on the axe automatically configure Thymeleaf TemplateResolver in addition to ViewResolver.

If y'all are non using @SpringBootApplication or running on Spring kicking version lower than 1.1 so y'all tin laissez passer on the axe exercise @EnableAutoConfiguration annotates to enable the auto-configuration characteristic of Spring Boot.


Another affair which is worth knowing virtually @EnableAutoConfiguration is that it allows y'all to selectively ignore surely classes from auto-configuration using exclude attribute equally shown below:

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

If the flat is non on the classpath, y'all tin laissez passer on the axe exercise the excludeName attribute of the @EnableAutoConfiguration annotation in addition to specify the fully qualified flat name, equally explained past times Ranga Karnan on  Learn Spring Boot inwards 100 Steps course. One of the best course of report for beginners to larn Spring boot.

Btw, this Spring Boot annotation is genuinely useful for experienced Spring Boot programmers who intend that Spring kicking is also opinionated in addition to desire to bring to a greater extent than or less 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 amongst @RunWith annotation of JUnit to essay a Service flat 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 flat instructs to charge the Spring application context defined inwards the PaymentConfiguration class.

Btw, fifty-fifty though it does a swell chore of loading Spring application context, it doesn't render total Spring kicking 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 in addition to loading of properties from external holding file like applicaiton.properties equally good equally other Spring Boot features. But, don't worry, at that spot is to a greater extent than or less other annotation which provides all of this in addition to y'all tin laissez passer on the axe exercise that to write a unit of measurement essay amongst Spring kicking 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 in addition to loads properties from application.properties file.

Btw, y'all should e'er exercise @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 bring seen inwards the in conclusion department but re-written using the @SpringApplicationConfiguration annotation this time. Again, I advise y'all cheque out the Spring Boot inwards Action mass to larn to a greater extent than virtually it, 1 of the best books to larn Spring Boot framework.

5.@ConditionalOnBean

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


5.1 @ConditionalOnMissingBean
Similarly, y'all bring @ConditionalOnMissingBean, which enables the configuration if the specified edible bean has non already been configured.

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


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


5.3 @ConditionalOnExpression
The Configuration is applied if the given Spring Expression Language (SpEL) appear 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, in addition to @ConditionalOnNotWebApplication which plant depending upon the presence in addition to absence of to a greater extent than or less conditions.

If y'all are interested to larn to a greater extent than virtually them, I advise to acquire out through Spring Framework 5: Beginner to Guru, 1 of the best course of report to larn Conditionals in addition to Spring Boot annotations.

That's all virtually to a greater extent than or less of the essential Spring Boot annotations every Java developer should know. If y'all are using Spring Boot for creating Spring-based Java spider web application so y'all volition come upward across these annotations every straightaway in addition to then. Just knowing what they do in addition to where y'all tin laissez passer on the axe exercise volition laissez passer on y'all confidence land reading in addition to writing Spring kicking code.

Further Learning
Learn Spring Boot
Master Java Web Services amongst Spring Boot
Master Hibernate in addition to JPA amongst Spring Boot inwards 100 Steps


Other Java in addition to Spring articles y'all may like

• 5 Spring Boot Features Every Java Developer Should Know (features)
• Top v Free Courses to larn Spring in addition to Spring Boot inwards 2019 (courses)
• 5 Course to Master Spring Boot online inwards 2019 (courses)
• 10 Things Java Developer should larn inwards 2019 (goals)
• 10 Tools Java Developers exercise inwards their day-to-day life (tools)
• 10 Tips to acquire a improve Java developer inwards 2019 (tips)
• 3 Best Practices Java Programmers tin laissez passer on the axe larn from Spring (best practices)
• 5 courses to larn Spring Boot in addition to Spring Cloud inwards 2019( courses)
• 3 ways to modify Tomcat port inwards Spring Boot (tutorial)
• 10 Spring MVC annotations Java developers should larn (annotations)
• 15 Spring Boot Interview Questions for Java Programmers (questions)

Thanks for reading this article so far. If y'all honour these Spring Boot annotations useful so delight portion amongst your friends in addition to colleagues. If y'all bring whatever questions or feedback so delight drib a note.