Fix Spring Autowired Injection Failure

Before addressing the issue of failed @Autowired injection, it is important to understand the possible reasons that may lead to injection failures. Here are some common reasons and solutions:

1. The class was not properly injected into the Spring container: make sure the class being injected is correctly annotated with @Component, @Service, @Repository, or other appropriate annotations, and is scanned into the Spring container.
2. The class dependencies were not injected correctly: make sure that the dependencies of the injected class (i.e. injected properties) are also properly annotated with @Component, @Service, @Repository, etc., and are scanned into the Spring container.
3. The access modifier of the class is incorrect: make sure that the access modifier of the injected class is public or protected so that Spring can access it correctly.
4. The class constructor was not injected correctly: If using constructor injection, ensure that the constructor is annotated with @Autowired and is properly scanned within the Spring container.
5. There are multiple implementations for the injected interface. If there are multiple implementations for an interface, you can use the @Qualifier annotation to specify the specific implementation for injection.
6. If the name of the property being injected is different from the name of the property in the class being injected into, you can use the @Qualifier annotation to specify the specific property name to be injected.
7. Sometimes injection failures may be caused by incompatible Spring versions. Try using a compatible Spring version to resolve the issue.

If none of the above methods can solve the injection failure issue, you can try using debugging tools (such as the debugging feature in IDE) to further examine the specific error message and identify the problem. Additionally, you can also add logging output in the Spring configuration file to better pinpoint the issue.

In conclusion, there could be many reasons for the failure of the injection, which require a case-by-case analysis and appropriate solutions to be taken.