Spring getter 和 setter 依赖？

Question

I would like to make sure if I understand this correctly. Spring needs a setter to inject a field reference? Couldn't it do it by just detecting it as a public field?

Is there an alternative to this. From what I understand Java EE's @Inject annotation can do this without any problem. But I have always been inclined more to Spring.

Answer 1

This depends on how you're creating your bean. Spring does not require setters. There are a number of other ways:

• Autowiring (with or without Qualifiers) via annotation at the field level
• Constructor injection (either by xml or annotations in the code)

Public fields (as you suggested) might work, though i have never tried it, and would advise against it even if it does.

Unfortunately, the XML approach does not look into private fields (that i know of). You either need to add a setter, use the constructor, or set up some sort of autowiring.

Keep in mind, autowiring can be combined with XML. Spring will pay attention to your wiring annotations even if you create your bean via xml (as opposed to something like @Component and component scanning).

Answer 2

It is not necessary to have Setter to inject a reference, you can use Autowire on a public variable of a class or on the setter method, u can also inject beans using constructor-arg which is a good way of injecting dependencies and autowiring can be done on Constructors also. @inject also does the same functionality as @autowired, however @Autowired has an additional behaviour where it internally also uses @required attribute, to see if the bean has a references and injected properly.

Answer 3

Spring provides several alternatives for DI besides setter injection. For example, you can use constructor injection . Alternatively, you can use Spring's @Autowired annotation for constructor, field or setter injection. Since you mentioned it, I guess that you would also be interested in knowing that Spring supports the @Inject annotation.