What is the Lazy annotation impact on spring boot services Injection?-CodePudding

I have an error about The dependencies of some of the beans in the application context form a cycle:.

and many answers suggest using @Lazy annotation to fix this problem

but what is the impact on the code after using @Lazy ??

The cycle happened because two services injected each other

and I read about @Lazy ,and how it fix this issue by @Lazy That is:

instead of fully initializing the bean, it will create a proxy to inject it into the other bean. The injected bean will only be fully created when it’s first needed.

CodePudding user response：

No matter which injection method you use, in all cases instead of a reference to a real dependency, a proxy object is provided.

It’s important to understand that if a relation is marked with @Lazy it doesn’t mean that creation of the dependent bean is postponed. When the dependent bean isn’t marked with @Lazy itself, it will be eagerly created by the Spring container. Such behavior leads to the conclusion that lazy injection should be mainly used together with lazy initialization.

source: https://www.javacodegeeks.com/2018/03/spring-lazy-annotation-use-cases.html

CodePudding user response：

This is to add to Abdalrhman's answer...

The @Lazy annotation is used to delay the initialization of a bean.

Delay until when? When it is needed. The inverse, if a bean is not annotated with @Lazy, its proxy object initializes it when the proxy object is initialized (on application context initialization). If a bean is annotated with @Lazy, its proxy object is still be initialized on application context initialization, but it underlying object is not initialized until an instance is requested. If it is a singleton bean, then the value is cached for later.

Why? It can be useful in situations where creating a bean is time-consuming or resource-intensive.

Note: You can make a single bean lazily-initialized by annotating the method. You can make all beans in a class (e.g., @Configuration) lazily-initialized by annotating the class.

Resources:

Fun fact: Some DI frameworks use lazy-initialization by default, specifically, Guice and HK2.