Google Guice的这两个绑定声明有什么区别? [英] what's the difference between these two binding declarations with Google Guice?

问题描述

两者之间有什么区别

bind(FooImpl.class).in(Scopes.SINGLETON);
bind(Foo.class).to(FooImpl.class);

和

bind(Foo.class).to(FooImpl.class).in(Scopes.SINGLETON);

使用Google Guice吗?

With Google Guice?

第二个声明在我正在处理的项目中的Singleton上创建两个实例. 此处引用

The second declaration create two instances on Singleton in a project I am working on. Reference here

推荐答案

在参考中到Google Guice文档:

In reference to Google Guice documentation:

在链接绑定中，作用域适用于绑定源，而不适用于 结合目标.假设我们有一个Applebees类，它同时实现了 Bar和Grill界面.这些绑定允许两个实例 这种类型，一种用于酒吧，另一种用于烧烤:

In linked bindings, scopes apply to the binding source, not the binding target. Suppose we have a class Applebees that implements both Bar and Grill interfaces. These bindings allow for two instances of that type, one for Bars and another for Grills:

bind(Bar.class).to(Applebees.class).in(Singleton.class);
bind(Grill.class).to(Applebees.class).in(Singleton.class);

这是因为范围适用于绑定类型(Bar，Grill)，而不是 满足绑定要求的类型(Applebees).只允许 要创建的单个实例，请在 该类的声明.或添加另一个绑定:

This is because the scopes apply to the bound type (Bar, Grill), not the type that satisfies that binding (Applebees). To allow only a single instance to be created, use a @Singleton annotation on the declaration for that class. Or add another binding:

bind(Applebees.class).in(Singleton.class);

因此，有可能在第二种方式中有两个FooImpl实例，但没有第一种方式来编写绑定.

So, It's possible to have two instances of FooImpl in the second way but not with the first way of writing the binding.

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