Many of your questions are in a form like this: badly worded pleas for someone else to post code without you showing what your have done (or tried) yourself. I assure you that by doing so, you will receive better responses than these [email protected], yes, I'd vote to re-open if the question would be rephrased so that it made more sense.
Try a couple of things yourself and, when getting stuck somewhere, post a specific question here (and post the code that didn't work).
You can use any build system you like when building apps with Spring, but the code you need to work with Maven is included here. Or you can build a single executable JAR file that contains all the necessary dependencies, classes, and resources, and run that.
If you’re not familiar with Maven, refer to Building Java Projects with Maven. This makes it easy to ship, version, and deploy the service as an application throughout the development lifecycle, across different environments, and so forth.
Like most Spring Getting Started guides, you can start from scratch and complete each step, or you can bypass basic setup steps that are already familiar to you. If you’re not familiar with either, refer to Building Java Projects with Gradle or Building Java Projects with Maven. Thymeleaf settings can be changed and overridden in a variety of ways depending on what you need to achieve, but the details are not relevant to this guide.
The Java programming language distinguishes between null and empty strings.An empty string is a string instance of zero length, whereas a null string has no value at all.An empty string is represented as are initialized with the value of the empty string by the Java Server Faces implementation.The Bean Validation model is supported by constraints in the form of annotations placed on a field, method, or class of a Java Beans component, such as a managed bean. User-defined constraints are called custom constraints. Several built-in constraints are available in the tag.Any managed bean that contains Bean Validation annotations automatically gets validation constraints placed on the fields on a Java Server Faces application’s web pages.Specifically validation should not be tied to the web tier, should be easy to localize and it should be possible to plug in any validator available.Considering the above, Spring has come up with a interface that is both basic and eminently usable in every layer of an application.Validating input received from the user to maintain data integrity is an important part of application logic.Validation of data can take place at different layers in even the simplest of applications, as shown in Developing a Simple Facelets Application.The purpose of this code is to produce a consistent method to validate user input, and not let the program proceed until the user has inputted a correct type.The class methods accept user input as string, attempt to convert that input to the expected type.