Java Programming language [closed]

How does Java handle form data validation and sanitization internally, and what are the best practices to prevent security vulnerabilities such as SQL Injection and XSS?

I am working on a Java-based web application (Servlets / JSP / Spring MVC) that processes user input from HTML forms. User input is typically received using objects such as HttpServletRequest, request parameters, and model binding in frameworks.

While Java provides methods like request.getParameter() to access form data, I want to understand how Java handles this data internally and what the recommended approach is for validating and sanitizing user input before using it in an application.

Many beginner examples directly retrieve form values and insert them into a database using SQL queries or display them on a web page. However, this approach can lead to serious security vulnerabilities such as SQL Injection, Cross-Site Scripting (XSS), and Cross-Site Request Forgery (CSRF) if input is not handled properly.

I would like a detailed explanation of:

How Java web applications receive and store form data using HttpServletRequest and request parameters

The difference between input validation and input sanitization in Java

When and how to use techniques such as:

Bean Validation (@NotNull, @Size, @Email)

Regular expressions

Encoding libraries (e.g., OWASP Encoder, Apache Commons Text)

The role of Prepared Statement in preventing SQL Injection

How output encoding helps prevent XSS in JSP / Thymeleaf / HTML pages

Common mistakes made by beginners when handling user input in Java web applications

Recommended best practices for securely processing form data in modern Java applications