Decorator Pattern with Spring

The decorator pattern is well known and described.
See for example https://en.wikipedia.org/wiki/Decorator_pattern

 The question is how can we implement easily the pattern with Spring.

 Lets just do an example.
 We have a SearchService which can be configuratively be switch on or off.

We have a simple interface

public interface SearchService{
    List find(Param p);
}

and a simple implementation

@Component
public class DefaultSearchService implements SearchService{
    public List find(Param p){
        repository.find(p);
    }
}

Our decorator logically implements the SearchService interface as well

@Component
public class SearchServiceDecorator implements SearchService{

    private final SearchService searchService;
    private final Config config;

    @Autowired
    public SearchServiceDecorator(SearchService searchService, Config config){
        this.searchService = searchService;
    }

    public List find(Param p){
        if(config.allowed())
            searchSerice.find(p);
    }
}

This will obviously not work. Spring cannot decide which version of SearchService to use. The solution is quite elegant:

@Component
@Primary
public class SearchServiceDecorator implements SearchService{

    private final SearchService searchService;
    private final Config config;

    @Autowired
    public SearchServiceDecorator(@Named("defaultSearchService")SearchService searchService, Config config){
        this.searchService = searchService;
    }

    public List find(Param p){
        if(config.allowed())
            searchSerice.find(p);
    }
}

The @Primary annotation, according to its Javadoc "Indicates that a bean should be given preference when multiple candidates * are qualified to autowire a single-valued dependency." The @Named allows to inject the decorator chain. Thats it :)