Example explanation of string boot and custom interceptor

I've learned about filters before, but the filters are for servlets. They are used in spring MVC and spring boot. In terms of functions, they don't feel very easy to use

Let's learn about interceptors

I Execution sequence of interceptors

1. Contents

2. Interceptor

In the interceptor, I added three (first, two, third), but the content is almost the same

Only when prehandle returns true will the following execution continue

Interceptor registration:

In order to verify the execution order, we use thymeleaf, and then access the properties passed in the background in the foreground. When accessing, the information will be printed to the console

Controller:

View:

When accessing localhost: 8080 / first / index, the response information will be output on the console

In this way, we can see the execution sequence of a single interceptor

1. Execute the prehandle method before the controller method is executed

2. Execute the action method of the controller

3. After executing the action, execute the posthandle method of the interceptor before parsing the view (if any)

4. Parse view

5. After parsing, execute the aftercompletion method

When registering multiple interceptors, the execution sequence is shown in the figure

II The interceptor implements permission verification

Similarly, add a permission interceptor first

Then register the permission interceptor

Add a login controller to the controller to provide login page and logout method

Here I made a login free annotation, which can be added to the controller or action

There is no need for anything in the annotation

Login page (the login page here is only for logout, so after visiting this page, it means that the login is successful)

Result presentation method:

In the browser, open first http://localhost:8080/login/index Page, and then access it in a new tab http://localhost:8080/first/index Page

You will find that you can access first / index

At this time, click the logout button on the login / index page, and then refresh the first / index page to directly jump to the login page

The above example explanation of string boot and custom interceptor is all the content shared by Xiaobian. I hope it can give you a reference and support more programming tips.