How Spring solves circular dependencies

Solution: 1. Temporary injection; 2. Use @Lazy annotation; 3. Refactor the code; 4. Use third-party libraries, etc. Detailed introduction: 1. Temporary injection: If the dependency between two Beans is temporary and only exists in a certain method, it can be solved by injecting it in the method. In this case, the IoC container will inject the Bean when the method is executed and destroy it immediately after execution, thus avoiding circular dependencies; 2. Use @Lazy annotation: When the dependency between two Beans is long-term, it needs to be maintained throughout the entire life cycle. Wait while maintaining.

# Operating system for this tutorial: Windows 10 system, Dell G3 computer.

The Spring framework solves the problem of circular dependencies through the IoC container. Circular dependencies occur when two or more beans depend on each other. In order to solve this problem, the Spring IoC container adopts the following strategies:

1. Temporary injection: If the dependency of two beans is temporary and only exists in a certain method, Then it can be solved by injecting it in the method. In this case, the IoC container will inject the Bean when the method is executed and destroy it immediately after execution, thus avoiding circular dependencies.

2. Use @Lazy annotation: When the dependency relationship between two Beans is long-term and needs to be maintained throughout the life cycle, you can use @Lazy annotation to resolve cyclic dependencies. The @Lazy annotation tells the IoC container to delay initializing the bean until the bean is used. In this way, when one Bean is initialized, another Bean may not have been initialized, thus avoiding circular dependencies.

3. Refactor the code: If the circular dependency is caused by an unreasonable code structure, the circular dependency can be eliminated by refactoring the code. For example, public methods and properties can be extracted into a new Bean, so that both original Beans depend on this new Bean, thus eliminating circular dependencies.

4. Use third-party libraries: Some third-party libraries provide solutions to solve circular dependencies, such as Google Guice and Spring's @InjectMocks annotation. These libraries and annotations can help developers solve circular dependency problems more easily.

To sum up, Spring solves the problem of circular dependencies through IoC containers, @Lazy annotations, code refactoring and the use of third-party libraries. Developers can choose the appropriate method to solve the circular dependency problem based on the specific situation.

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