如何定义“默认"广告代码?在HK2中实施?

问题描述

我正在使用HK2来解决我的Jersey/Jetty Web服务中服务的依赖关系.我遇到一种情况，对于一个特定的接口，我想使用特定的实现作为默认"实现. 默认"是指没有名称或限定词-如果未在字段或参数的顶部指定任何注释，则会得到此名称.但是，在一些非常特殊的情况下，我想提供一种可选的实现，该实现将带有注释.

I am using HK2 to resolve dependencies of services in my Jersey / Jetty web service. I have a situation where for one particular interface, I want to use a specific implementation as a "default" implementation. By "default" I mean no names or qualifiers - it is what you get if you do not specify any annotations on top of the field or argument. However, in a few very specific situations, I want to provide an alternative implementation that will be qualified with an annotation.

作为实验的结果，我实际上通过在绑定中使用ranked()限定符使它可靠地工作.看来最高等级成为默认值.但是，我不明白为什么它会起作用，而且我担心我正在编写的代码取决于HK2的未记录实现细节，当我们更新版本时，HK2可能会更改.

As a result of my experimentation I have actually got this to work reliably by using the ranked() qualifier in my bindings. It appears the highest rank becomes the default. However, I do not understand why it works, and I am concerned I am writing code that depends on an undocumented implementation detail of HK2 that could change when we update versions.

这是我正在做的有趣部分的一个精心设计的示例. ranked()是我应该用来指定服务的默认"和带注释的变体吗?我应该使用其他技术吗?

Here's a contrived example of the interesting parts of what I am doing. Is ranked() what I should be using to specify "default" and annotated variants of a service? Should I be using another technique?

public interface IFoo {
    public String getString();
}

public class DefaultImpl implements IFoo {
    public String getString() {
        return "Default Implementation";
    }
}

public class AnnotatedImpl implements IFoo {
    public String getString() {
        return "Annotated Implementation";
    }
}

public class Bindings extends AbstractBinder {

     @Override
     public void configure() {
         ServiceBindingBuilder<DefaultImpl> defaultImpl =
             bind(DefaultImpl.class)
                 .to(IFoo.class);

         defaultImpl.ranked(9);

         ServiceBindingBuilder<AnnotatedImpl> annotatedImpl =
             bind(AnnotatedImpl.class)
                 .qualifiedBy(new MyAnnotationQualifier())
                 .to(IFoo.class);

         annotatedImpl.ranked(1);
     }
}

public class MyService {

    @Inject
    public MyService(
        IFoo defaultImplementation,
        @MyAnnotation
        IFoo annotatedImplementation) {

        // ... my code here ...
    }
}

推荐答案

我偶然发现了HK2网站上的一些文档，这些文档与我所看到的行为一致.

I stumbled across some documentation on HK2's website that is consistent with the behavior that I am seeing.

源

因此，我在绑定上正确使用了ranked().这是控制HK2定义为向我的从属服务注入的默认"(或最佳")服务的两种方法之一.

Therefore, I am using ranked() on my bindings correctly. It is one of the two ways to control what HK2 defines as the "default" (or "best") service to inject into my dependent services.

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