枚举以返回接口的实现

Question

我有一个名为HeaderProvider的接口及其实现，

interface HeaderProvider {
    Map<String, String> getHeaders();
}

class AHeaderProvider implements HeaderProvider {
...
}
class BHeaderProvider implements HeaderProvider {
...
}

实现是 Spring 托管 bean。 现在我有一个枚举 URLType

enum URLType{
A,
B....
}

有什么办法可以在枚举中使用像HeaderProvider getHeaderProvider()这样的方法来返回正确的实现吗？

Answer 1

只需将HeaderProvider成员添加到 枚举

public enum URLType {
    A(new AHeaderProvider()), B(new BHeaderProvider());

    private HeaderProvider provider;

    private URLType(HeaderProvider provider) {
        this.provider = provider;
    }

    public HeaderProvider getHeaderProvider() {
        return provider;
    }
}

Answer 2

我认为你可以这样做。

@Component
public class AHeaderProvider implements HeaderProvider, InitializingBean {

    private static HeaderProvider headerProvider;

    public static HeaderProvider getHeaderProvider() {
        return headerProvider;
    }

    @Override
    public void afterPropertiesSet() throws Exception {
        headerProvider = this;
    }

    @Override
    public Map<String, String> getHeaders() {
        return new HashMap<>();
    }
}

@Component
public class BHeaderProvider implements HeaderProvider, InitializingBean {

    private static HeaderProvider headerProvider;

    public static HeaderProvider getHeaderProvider() {
        return headerProvider;
    }

    @Override
    public void afterPropertiesSet() throws Exception {
        headerProvider = this;
    }

    @Override
    public Map<String, String> getHeaders() {
        return new HashMap<>();
    }
}

public enum UrlType {

    A(AHeaderProvider.getHeaderProvider()),

    B(BHeaderProvider.getHeaderProvider());
    private HeaderProvider headerProvider;

    UrlType(HeaderProvider headerProvider) {
        this.headerProvider = headerProvider;
    }


    public HeaderProvider getHeaderProvider() {
        return headerProvider;
    }
}