spring - 使用工厂方法实例化 Spring bean 的原因是什么？

Question

我知道Spring中有基于构造函数的注入(inject)和基于setter的注入(inject)。什么时候应该使用工厂方法来注入(inject) Bean？

Answer 1

这更像是一个设计问题，取决于您的架构。

如果您有带有静态工厂方法的类，为什么要添加不必要的构造函数来破坏设计以适应 DI 框架？

它不灵活，因此 Spring 支持这两种方式。

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摘自Joshua Bloch “Effective Java” :

Item 1: Consider static factory methods instead of constructors.

Static factory methods advantages:

• They have names.
• They are not required to create a new object each time they are invoked.
• They can return an object of any subtype of their return type.
• They reduce verbosity of creating parameterized type instances.

Static factory methods disadvantages:

• When providing only static factory methods, classes without public or protected constructors cannot be subclassed.
• They are not readily distinguishable from other static methods