Choose which implementation to inject at runtime spring

Question

I have the following classes:

public interface MyInterface{}

public class MyImpl1 implements MyInterface{}

public class MyImpl2 implements MyInterface{}

public class Runner {
        @Autowired private MyInterface myInterface;
}

What I want to do is decide, whilst the app is already running (ie not at startup) which Implementation should be injected into Runner .

So ideally something like this:

ApplicationContext appContext = ...
Integer request = ...

Runner runner = null;
if (request == 1) {
        //here the property 'myInterface' of 'Runner' would be injected with MyImpl1
        runner = appContext.getBean(Runner.class) 
}
else if (request == 2) {
        //here the property 'myInterface' of 'Runner' would be injected with MyImpl2
        runner = appContext.getBean(Runner.class)
}
runner.start();

What is the best way to accomplish this?

Answer 1

Declare implementations with @Component("implForRq1") and @Component("implForRq2")

Then inject them both and use:

class Runner {

    @Autowired @Qualifier("implForRq1")
    private MyInterface runnerOfRq1;

    @Autowired @Qualifier("implForRq2")
    private MyInterface runnerOfRq2;

    void run(int rq) {
        switch (rq) {
            case 1: runnerOfRq1.run();
            case 2: runnerOfRq2.run();
            ...

        }
    }

}

...

@Autowired
Runner runner;

void run(int rq) {
    runner.run(rq);
}