Servlets · Lesson 11

JSP Basics and Integration

What JSP Adds

JSP, or JavaServer Pages, is a server-side view technology for rendering HTML from Java web applications. A servlet prepares view data, and the JSP displays that data with tags and expression language. This separation is easier to maintain than building large HTML strings in a servlet.

Passing Data to a JSP

A servlet can place values in request attributes and forward to a JSP under WEB-INF. The view reads the attributes with Expression Language and should avoid business logic.

import jakarta.servlet.RequestDispatcher;
import jakarta.servlet.ServletException;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import java.io.IOException;

public class CourseServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        request.setAttribute("courseTitle", "Servlet Fundamentals");
        request.setAttribute("lessonCount", 12);
        RequestDispatcher view = request.getRequestDispatcher("/WEB-INF/views/course.jsp");
        view.forward(request, response);
    }
}

A JSP can render the attributes with expressions such as ${courseTitle} and ${lessonCount}. Standard tag libraries are preferable to scriptlets because they keep Java code out of the HTML view.

Servlet and JSP Roles

Common Mistake and Practices

Common Mistake: Writing Java scriptlets and SQL directly inside a JSP. This mixes responsibilities, makes testing difficult, and can expose sensitive implementation details in a presentation file.

• Keep JSPs focused on presentation.
• Use Expression Language and tag libraries.
• Put JSP views under WEB-INF when they require controller setup.
• Escape user-generated output.
• Keep view models small and intentional.

Real-World Use Case

A course servlet loads a learner's progress and forwards a view model to a JSP. The JSP renders lesson links and progress indicators, while the service layer owns completion rules and the repository owns database access.