First, and most important – all Spring beans are managed – they “live” inside a container, called “application context”. Second, each application has an entry point to that context. Web applications have a Servlet, JSF uses a el-resolver, etc. Also, there is a place where the application context is bootstrapped and all beans – autowired. … Read more
Basically Spring is a framework for dependency-injection which is a pattern that allows building very decoupled systems. The problem For example, suppose you need to list the users of the system and thus declare an interface called UserLister: public interface UserLister { List<User> getUsers(); } And maybe an implementation accessing a database to get all … Read more
@Component Preferable for component scanning and automatic wiring. When should you use @Bean? Sometimes automatic configuration is not an option. When? Let’s imagine that you want to wire components from 3rd-party libraries (you don’t have the source code so you can’t annotate its classes with @Component), so automatic configuration is not possible. The @Bean annotation … Read more
The field annotated @Autowired is null because Spring doesn’t know about the copy of MileageFeeCalculator that you created with new and didn’t know to autowire it. The Spring Inversion of Control (IoC) container has three main logical components: a registry (called the ApplicationContext) of components (beans) that are available to be used by the application, … Read more
<context:annotation-config> is used to activate annotations in beans already registered in the application context (no matter if they were defined with XML or by package scanning). <context:component-scan> can also do what <context:annotation-config> does but <context:component-scan> also scans packages to find and register beans within the application context. I’ll use some examples to show the differences/similarities. … Read more
Assuming here you’re referring to the javax.inject.Inject annotation. @Inject is part of the Java CDI (Contexts and Dependency Injection) standard introduced in Java EE 6 (JSR-299), read more. Spring has chosen to support using the @Inject annotation synonymously with their own @Autowired annotation. So, to answer your question, @Autowired is Spring’s own annotation. @Inject is … Read more
JpaRepository extends PagingAndSortingRepository which in turn extends CrudRepository. Their main functions are: CrudRepository mainly provides CRUD functions. PagingAndSortingRepository provides methods to do pagination and sorting records. JpaRepository provides some JPA-related methods such as flushing the persistence context and deleting records in a batch. Because of the inheritance mentioned above, JpaRepository will have all the functions … Read more
As said in docs either set server.port as system property using command line option to jvm -Dserver.port=8090 or add application.properties in /src/main/resources/ with server.port=8090 For a random port use: server.port=0 Similarly add application.yml in /src/main/resources/ with: server: port: 8090
From Spring Documentation: The @Repository annotation is a marker for any class that fulfils the role or stereotype of a repository (also known as Data Access Object or DAO). Among the uses of this marker is the automatic translation of exceptions, as described in Exception Translation. Spring provides further stereotype annotations: @Component, @Service, and @Controller. … Read more