[FIXED] How to Autowired an instance of a subclass based on a property that is defined in property file

Issue

I use SpringBoot 2.2.2.RELEASE (pretty old one) and I have the following requirements:

I have a @Service class, which I would like to expand its constructor by adding an interface. When the application loads I would like the correct instance of the interface to be @Autowired based on some property I would define in a property file. so this is basically a Factory which instantiate classes by some property that defined in property file.

Here is a snippet of how I would imagine it to work:

@Service
class MyService {

   @Autowired
   public MyService(Shape shape) { ...}
}


interface Shape { ...}

class Circle implements Shape { ... }

class Rectangle implements Shape { ... }

The magic should resides in some Factory class that reads a property from property file and accordingly instantiate one of the subclasses of Shape.

Each instance of this application runs on a dedicated machine (EC2) with its own unique property files.

Is there something like this built into Spring Boot?

Any suggestions would be appreciated!

Solution

One way to achieve it is to use @ConditionalOnProperty annotation to instantiate beans when properties have a specific value. You could use matchIfMissing = true to determine default behavior.

@Bean
@ConditionalOnProperty(name = "shape", havingValue = "circle", matchIfMissing = true)
public Shape circleShape() {
    return new Circle();
}

@Bean
@ConditionalOnProperty(name = "shape", havingValue = "rectangle")
public Shape rectangleShape() {
    return new Rectangle();
}

Answered By - Alex
Answer Checked By - Gilberto Lyons (JavaFixing Admin)