What is the principle of spring interceptor

The principle of Spring interceptor is mainly based on Spring's AOP framework. The interceptor plays an important role in Spring MVC and is mainly used to intercept user requests and process them accordingly. The steps of interceptor principle: 1. Define interceptor; 2. Configure interceptor; 3. Interceptor chain; 4. Execute interception; 5. Return processing; 6. Exception handling. Interceptors also need to be used with caution to avoid over-reliance and use that will lead to a decrease in system complexity and performance.

The operating system for this tutorial: Windows 10 system, DELL G3 computer.

The principle of Spring interceptor is mainly based on Spring's AOP (aspect-oriented programming) framework. Interceptors play an important role in Spring MVC. They are mainly used to intercept user requests and process them accordingly, such as permission verification, logging of request information, determining whether the user is logged in, etc.

The interceptor principle can be divided into the following steps:

1. Define the interceptor: Interceptors usually implement HandlerInterceptor interface or an implementation class that inherits the HandlerInterceptor interface (such as HandlerInterceptorAdapter).

2. Configure the interceptor: In the Spring configuration file, you need to configure the interceptor class, specify which URLs need to be intercepted, and which interceptor to use for processing.

3. Interceptor chain: When a user initiates a request, the request will pass through all interceptors in the interceptor chain in sequence. Each interceptor will execute its preHandle method to process the request.

4. Execution interception: When the request reaches the target processor, all pre-notifications (preHandle method) will be executed first, and then the business logic of the target processor will be executed. If the preHandle method of an interceptor returns false, it means that the request has been intercepted and will not continue to execute.

5. Return processing: After the target processor finishes processing the request, all post-notifications (postHandle method) will be executed in sequence. Then a response is returned to the user.

6. Exception handling: If an exception occurs during processing, you can execute the afterCompletion method for exception handling.

Through the above steps, the Spring interceptor can intercept and process user requests, thereby enhancing system security, logging and other functions. At the same time, through the AOP framework, Spring interceptors can also implement common functions across multiple applications, such as permission control, logging, etc.

It should be noted that the use of interceptors also needs to be cautious to avoid over-reliance and use that will lead to a decrease in system complexity and performance. Therefore, when designing and using interceptors, you need to carefully consider its applicable scenarios and scope of influence, as well as how to properly configure and use interceptors.

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