查找API NetBeans Platform + Maven:松散耦合的模块 [英] Lookup API NetBeans Platform + Maven: loosely coupled modules

问题描述

我正在开发NetBeans平台应用程序，并希望使用lookup api来获取特定接口的实现，同时仍然保持所有组件的松散耦合. 但是查询找不到任何服务提供商.

I'm developing a NetBeans platform application and want to use lookup api to get implementations for specific interfaces, still keeping everything loosely coupled. But the lookup can't find any service provider.

好，我创建了:

• 一个模块(A)，其中包含两个接口(Prot，Com)和一个用于显示一些GUI的类.
• 包含接口Prot的实现的模块(B)
• 包含接口COM实现的模块(C).

要注册实现，我使用了 @ServiceProvider 批注. 对于模块B中的演说:

To register an implementation i used @ServiceProvider annotation. For Examble in Module B:

@ServiceProvider(service = Prot.class)
class ProtImpl implements Prot
{
   @Override
   ...
}

如果您使用@ServiceProvider注释，则定义了默认构造函数. 我定义了对模块A的依赖关系，因为B需要了解有关接口的一些知识.

I defined the default-constructor, that is needed, if you use @ServiceProvider annotation. I defined a dependency on Module A because B need to know something about the interface.

模块A中的查找说明:

private void printImplNames()
{
   Prot prot = Lookup.getDefault().lookup(Prot.class);
   prot.getName(); // <--- Null-Pointer
}

现在，如果我查找接口Prot的实现，则会得到一个空指针异常.换句话说，没有注册实现.查找找不到任何服务提供商. 注释processcor可以正常工作，因为已在META-INF/.../目录中创建了文件.

Now if I look up the implementation of interface Prot, I get a null pointer exception. With other words, there is no implementation registered. The lookup cant find any service provider. Annotation processcor works fine, because files in META-INF/.../ directory were created.

唯一可行的方法是在模块A BUT 中定义对模块B的依赖关系，这样就失去了松散耦合模块的方面.

The only thing that seems to work is to define a dependency on Module B in Module A BUT in this way the aspect of loosley coupled modules is lost.

我遵循了NetBeans Platform网站和NetBeans Platform 7 Book上的指示，但似乎无济于事.希望有人能帮助我解决这个问题.

I followed intructions on NetBeans Platform Website and NetBeans Platform 7 Book but nothing seems to work. Hope somebody can help me to solve that problem.

谢谢;)

推荐答案

我在GitHub上针对这种情况创建了一个工作示例.

I've created a working example for this situation located at GitHub.

https://github.com/flinkgutt/stackoverflow/tree/master/LooseCoupling

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