Switch beans with @ConditionalOnExpression and SpEL regular expressions

For example, suppose you want to switch beans that are registered based on the values in the spring-boot properties file. In addition, I want to switch the registered bean depending on when the property value matches a certain regular expression.

In this case, use a regular expression in SpEL of @ ConditionalOnExpression.

Source code

Property file

Now suppose a property value can take `v0004``` from` v0001```.

src/main/resources/application.yml

oncondition:
#  value: v0001
#  value: v0002
#  value: v0003
  value: v0004

At this time, it is assumed that the bean is to be switched between the case of `` v0001``` to v0003``` and the case of `v0004```.

Classes that can be switched

Make a suitable interface.

public interface ISample {
    String value();
}

import org.springframework.boot.autoconfigure.condition.ConditionalOnExpression;
import org.springframework.stereotype.Component;

@Component
@ConditionalOnExpression("#{'${oncondition.value}' matches 'v000[123]'}")
public class Value123 implements ISample {
    @Override
    public String value() {
        return "value123";
    }
}

import org.springframework.boot.autoconfigure.condition.ConditionalOnExpression;
import org.springframework.stereotype.Component;

@Component
@ConditionalOnExpression("#{'${oncondition.value}' matches 'v0004'}")
public class Value4 implements ISample {
    @Override
    public String value() {
        return "value4";
    }
}

@ConditionalOnExpression is enabled when SpEL matches. here${oncondition.value}Browse the properties with the regular expression matches'v000[123]'Is described. This makes oncondition.value is v0001,v0002,This class is valid for v0003.

## Run
 The startup class to check at the end.

```java
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class App implements CommandLineRunner {
    public static void main(String[] args) {
        SpringApplication.run(App.class, args);
    }

    @Autowired
    ISample hoge;
    
    @Override
    public void run(String... args) throws Exception {
        System.out.println(hoge.value());
    }
}