如何动态创建多个相同类型的bean然后收集/自动装配它们

Question

let's say that in my spring(boot) yaml config file I have a list of commands:

commands: [add,delete,copy,move] 

and the corresponding class in my spring(boot) project:

public class Command {

    private String name;

    public Command(String name) {
        this.name = name;
    }

    public void execute() {
        System.out.println(name);
    }

    public String getName() {
        return name;
    }

}

How can I dynamically/adaptively generate the right number of command beans, then gather/autowire them in a separate class as below?

public class Menu {

   @Autowired
   List<Command> commands;

   public void display() {
       commands.forEach(cmd -> System.out.println(cmd.getName());
   }

}

Thank you very much in advance for your time and your expertise.

Regards

Answer 1

For dynamic bean registration, you can use ImportBeanDefinitionRegistrar .

The code will be like this:

import java.util.List;
import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.beans.factory.support.BeanDefinitionBuilder;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Import;
import org.springframework.context.annotation.ImportBeanDefinitionRegistrar;
import org.springframework.core.type.AnnotationMetadata;

@Configuration
@Import(CommandsConfiguration.Registrar.class)
public class CommandsConfiguration {

    static class Registrar implements ImportBeanDefinitionRegistrar {

        @Override
        public void registerBeanDefinitions(AnnotationMetadata annotationMetadata, BeanDefinitionRegistry registry) {
            final List<String> commands = // read commands from environemnt/config
            for (String command : commands) {
                final String beanName = command + "Command";
                final BeanDefinition beanDefinition = BeanDefinitionBuilder
                    .genericBeanDefinition(Command.class, () -> new Command(command))
                    .getBeanDefinition();
                registry.registerBeanDefinition(beanName, beanDefinition);
            }
        }
    }
}