构建器模式与依赖注入（例如通过Guice） [英] Builder pattern vs. Dependency Injection (for instance via Guice)

问题描述

我正在开发一个简单的树形结构数据库，我通常通过Builder（Builder模式）设置依赖项或可选设置。现在我不确定何时使用Guice，何时使用Builder模式以及何时使用静态工厂方法而不是构造函数本身。我已经多次阅读过Effective Java，我认为它至少提到了不暴露构造函数的许多优点。是时候重读了; - ）

I'm developing a simple tree-structured database and I'm usually setting dependencies or optional settings via a Builder (Builder pattern). Now I'm not sure when to use for instance Guice, when to use the Builder pattern and when to use a static factory method instead of the constructor itself. I've read Effective Java several times and I think it mentions at least a lot of advantages for not exposing the constructor. It's time to reread ;-)

那么，你知道哪些案例可以清楚地区分吗？我不应该暴露构造函数？因此，例如在每种情况下写公共静态Foo getInstance（...）{return new Foo（...）} ？

So, do you know of cases which are clearly distinguishable? And shouldn't I expose the constructor? Thus for instance in every case write public static Foo getInstance(...) { return new Foo(...)}?

推荐答案

我坚信你不需要为一切使用依赖注入。

I'm a firm believer in that you don't need to use dependency injection for everything.

• 对于 LookupService ，这很自然 inject a Dictionary ，以便可以通过配置交换其实现。

• For a LookupService it would be natural inject a Dictionary such that its implementation can be swapped out by configuration.

另一方面，对于防火墙。它很自然地创建自己的 FireWallRules ，可能是通过提供的 Factory 或生成器。

For a Firewall on the other hand. It would be natural for it to create its own FireWallRules, perhaps through a supplied Factory or a Builder.

作为指导，注入 configure 所需的内容，不要自动注入其他一切。

As a guideline, inject what you need to configure, don't automatically inject everything else.

考虑 静态工厂（*） 何时

Consider a static factory (*) when

• 需要命名构造逻辑。例如， Lists.newArrayList（）


• 构造非常复杂，不属于类本身


• 不需要工厂配置，工厂有没有副作用

• named construction logic is desired. E.g., Lists.newArrayList()
• the construction is so complicated it doesn't belong in the class itself
• no configuration of the factory is required, and the factory has no side effects

考虑 实例工厂 何时

Consider instance factories when

• 复杂实例化逻辑


• 需要工厂配置


• 使用 AbstractFactory 设计模式


• 需要在整个程序生命周期中创建其他对象

• there is complex instantiation logic
• configuration of the factory is needed
• using AbstractFactory design pattern
• there's need to create additional objects throughout the programs lifecycle

考虑 builder 何时

Consider a builder when

• 有复杂的参数选择。例如，5个参数，其中一些是可选的。

（*） 静态方法并不总是可测试的，在我看来，一个人的存在总是有动力的。
工厂的典型用例是减少耦合。通过使用静态工厂，该功能完全丢失。

(*) Static methods are not always testable and the presence of one should in my opinion always be motivated. A typical usecase for a factory is to decrease coupling. By using a static factory that ability is completely lost.

这篇关于构建器模式与依赖注入（例如通过Guice）的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！