In -depth understanding of the implementation principle of VAADIN license checker

In -depth understanding of the implementation principle of VAADIN license checker When developing web applications, the framework of the operation interface is crucial.Vaadin is an open source Java framework that provides a highly customized user interface component library that allows developers to write web applications in Java language.Vaadin provides many useful functions, including permit checkers to verify the license of the application. The VAADIN license checker is a function used to verify the user application permit.It can check the effectiveness of the license, the date of expiration, the limit of use, etc.The VAADIN framework allows developers to use a custom license checker to achieve their own logic to meet their specific needs. The implementation principle of the license checker is as follows: 1. Implement a custom license checker class: First of all, you need to create a class that implements the LicenseChecker interface of Vaadin.The interface defines the method for verifying the license. The following is an example: public class MyLicenseChecker implements LicenseChecker { @Override public boolean isLicenseValid(License license) { // Realization of the logic of license verification Return true; // Replace it with actual logic } } 2. Registration license checker: In the entrance point of your Vaadin application, you need to register a custom license checker.Vaadin uses a dedicated VaadinServiceInitListener interface to monitor the initialization of Vaadin services. The following is an example: public class MyApplicationInitListener implements VaadinServiceInitListener { @Override public void serviceInit(ServiceInitEvent event) { event.getSource().addSessionInitListener(e -> { // Register a custom license checker e.getSession().addUIProvider(new MyUIProvider()); }); } } 3. Use a custom license checker: In your VAADIN application, you can use a registered custom license checker. The following is an example: @Push @VaadinServletConfiguration(productionMode = false, ui = MyUI.class) public class MyUI extends UI { protected void init(VaadinRequest request) { // Get the current liveChecker LicenseChecker licenseChecker = VaadinService.getCurrent().getInstantiator().getOrCreate(MyLicenseChecker.class); // Use the license checker to verify the license if (licenseChecker.isLicenseValid()) { // Effective logic of the license } else { // The logic of invalid permit } } } In the above code example, we created a custom licenses called MylicenseChecker, and implemented the ISLicensevalid method.Then, in the MyApplicationInitlistener class, we registered a custom license checker.Finally, in the INIT method of the MyUI class, we obtained the current LicenseChecker instance and used it to verify the effectiveness of the license. Through in -depth understanding of the implementation principle of the VAADIN license checker, you can customize verification logic according to actual needs and ensure that your application is compliant in license.During the development process, you can also use the license checker to provide more functions, such as restricting the probation period, controlling access permissions, etc. To sum up, the VAADIN license checker is a very useful function that helps developers to verify the application of the application.By creating a custom license checker class, and registering and using it in the application, you can easily implement the license verification logic and meet specific needs.