CODEWITHSUNDEEP
javaspringannotations
Raunak Agarwal
Raunak Agarwal

Reputation: 7228

Implementing Dependency Injection using Custom Annotation

I am working on a core java framework. I don't want to create instances directly inside the class which is why I want to use dependency injection.

I am thinking of declaring my custom annotations on the fields to be instantiated. And having a call back function which would create an instance and inject it into the field.

I had tried to create a custom annotation. But looks like there's no direct way to get a callback on the declared annotation. So, I was trying to scan the classes for that. But I ended up with this problem Java Scanning Class for Annotation using Google Reflections

Please let me know if this is the right way of achieving this.

Upvotes: 1

Views: 1503

Answers (1)

gerrytan
gerrytan

Reputation: 41113

Since your question is tagged 'Spring', you can use Spring Framework's bean annotations (@Component / @Service / @Repository / ...), classpath scanning and @Autowired.

For example:

Setup classpath scanning on your spring config xml:

<context:component-scan base-package="com.mycompany.myapp" />

Create your bean to be scanned. Spring container will automatically create a singleton instance of this bean using default constructor:

@Repository
public class FooDAO {
  ...
}

Inject reference to above DAO instance using DI + autowiring

@Service
public class FooService {

  @Autowired private FooDAO fooDAO;

  ...
}

Upvotes: 1

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