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SUBSCRIBE TO RAM N JAVA 🔔Spring Boot Form Validation & Data Binding with FreeMarker
Building forms is a fundamental part of web development. In this tutorial, we will learn how to handle user data safely using Form Validation and Data Binding in a Spring Boot application using the FreeMarker template engine.
What is Data Binding?
Data binding is the process that takes the values entered by a user in an HTML form and automatically maps them to a Java object (often called a Command Object or DTO). This means you don't have to manually pull every single field out of the request!
Why is Validation Important?
Never trust user input! Validation ensures that the data being sent to your server meets your requirements (like making sure an email is valid or a password is long enough) before you try to save it to a database.
Key Components of this Project
- User Model: A simple POJO with Hibernate Validator annotations like
@NotEmptyand@Size. - FreeMarker Template: Our HTML-based view that displays the form and any validation error messages.
- Controller: The brain that handles the
GETrequest to show the form and thePOSTrequest to process it. - BindingResult: A special Spring object that holds the results of the validation.
Implementation Steps
1. Add Dependencies: Include spring-boot-starter-freemarker and spring-boot-starter-validation in your pom.xml.
2. Annotate the Model: Use standard validation annotations on your fields.
3. Handle the POST: In your controller method, use @Valid before your model argument to trigger the validation check.
4. Display Errors: In your FreeMarker (.ftlh) file, use the bind macros to show errors next to the relevant fields.
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