In this post, we will create a Spring context and will get a bean object from it.
What is Spring context?
Spring context is also termed as Spring IoC container which is responsible for instantiate, configure and assemble the beans by reading configuration meta data from XML, Java annotations and/ or Java code in configuration files.
Technologies used
Spring 4.3.6.RELEASE, Maven Compiler 3.6.0 and Java 1.8
We will first create a simple maven project. You can select the maven-archtype-quickstart as archtype.
Adding dependencies in pom.xml
We will add spring-framework-bom in the dependency management.
<dependencyManagement> <dependencies> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-framework-bom</artifactId> <version>4.3.6.RELEASE</version> <type>pom</type> <scope>import</scope> </dependency> </dependencies> </dependencyManagement>
The benefit of adding this are to manage the version of the added spring dependencies from one place. By this, you can omit mentioning version number for spring dependencies.
<dependency> <groupId>org.springframework</groupId> <artifactId>spring-context</artifactId> <scope>runtime</scope> </dependency>
Now, we will create a class GreetingService
which is eligible to get registered as bean in Spring context.
@Service public class GreetingService { private static final Logger logger = Logger.getLogger(GreetingService.class.getName()); public GreetingService() { } public void greet() { logger.info("Gaurav Bytes welcomes you for your first tutorial on Spring!!!"); } }
@Service
annotation at class-level means that this is service and is eligible to be registered as bean in Spring context.
Instantiating a container
Now, we will create object of Spring context. We are using AnnotationConfigApplicationContext
as spring container. Also, there exists other spring container like ClassPathXmlApplicationContext
, GenericGroovyApplicationContext
etc. which we will discuss in future posts.
ConfigurableApplicationContext context = new AnnotationConfigApplicationContext( "com.gauravbytes.hellogb.service");
As you see at the time of object contruction of AnnotationConfigApplicationContext
, I am passing one string parameter. This parameter ( of varags type) is the basePackages which spring context will scan for bean registration.
Now, we will get object of bean by calling getBean()
on spring context.
GreetingService greetingService = context.getBean(GreetingService.class); greetingService.greet();
At last, we are closing the spring container by calling close()
.
context.close();
We have also included maven-compiler-plugin in pom.xml to compile the java sources with the configured java version (in our case it is Java 1.8).
You can also find the example code on Github.
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