java - 为什么我必须在 @Configuration 注释注释的 Spring 配置类中有一个默认构造函数？

Question

我正在学习 Spring Core 认证，关于提供的学习资料，我有这个问题，但我无法给出答案。

Why must you have to have a default constructor in your @Configuration annotated class?

我没有在 @Configuration 注释注释的配置类中声明任何构造函数。默认构造函数是父类(super class)继承的那个？或者是什么？为什么我必须有一个默认构造函数而我不能覆盖它？

Tnx

Answer 1

根据official spring javadoc , spring @Configuration 注解的类需要有默认的无参数构造函数

@Configuration classes must have a default/no-arg constructor and may not use @Autowired constructor parameters. Any nested configuration classes must be static

原因是spring使用CGLIB to proxy @Configuration类，在 Spring 中有限制，that classes proxied with CGLIB prior to version 4 are required to have default no-args constructor .

Prior to Spring 4, CGLIB-based proxy classes require a default constructor. And this is not the limitation of CGLIB library, but Spring itself. Fortunately, as of Spring 4 this is no longer an issue. CGLIB-based proxy classes no longer require a default constructor.