JSP: How to check if a user is logged in?

To pass some parameter(s) to the included JSP:

<jsp:include page="somePage.jsp" >
    <jsp:param name="param1" value="someValue" />
    <jsp:param name="param2" value="anotherParam"/>
    ....
</jsp:include>

You are already doing it.

OK, the details of the question is not very clear, but I get the idea.
One of the solutions could be the following.

In your Login action, if the authentication was successful, create HttpSession and set an attribute for the authenticated User:

if (/* authentication was successfull */) {
    request.getSession().setAttribute("loggedInUser", user);
    ...
}

And in the code where you are controlling if the user is logged in just check the presence of the appropriate HttpSession attribute:

HttpSession session = request.getSession(false);
if (session == null || session.getAttribute("loggedInUser") == null) {
    // user is not logged in, do something about it
} else {
    // user IS logged in, do something: set model or do whatever you need
}

Or in your JSP page you can check if the user is logged in using JSTL tags as showed by BalusC in the example here:

...
<c:if test="${not empty loggedInUser}">
    <p>You're still logged in.</p>
</c:if>
<c:if test="${empty loggedInUser}">
    <p>You're not logged in!</p>
</c:if>
...

Filters to the rescue

But usually, you check if the user is logged in to restrict access to some pages (so only authenticated user could access them). And you write some class that implements javax.servlet.Filter.

Here is an example of the LoginFilter from one of my projects:

package com.example.webapp.filter;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

/**
 * The purpose of this filter is to prevent users who are not logged in
 * from accessing confidential website areas. 
 */
public class LoginFilter implements Filter {

    /**
     * @see Filter#init(FilterConfig)
     */
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {}

    /**
     * @see Filter#doFilter(ServletRequest, ServletResponse, FilterChain)
     */
    @Override
    public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest) req;
        HttpServletResponse response = (HttpServletResponse) res;

        HttpSession session = request.getSession(false);
        if (session == null || session.getAttribute("loggedInUser") == null) {
            response.sendRedirect(request.getContextPath() + "/login.jsp");
        } else {
            chain.doFilter(request, response);
        }
    }


    /**
     * @see Filter#destroy()
     */
    @Override
    public void destroy() {}

}

In this project I used plain servlets and JSP without Spring, but you'll get the idea.

And of course, you must configure web.xml to use this filter:

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
    version="3.0">
    ...
    <filter>
        <filter-name>Login Filter</filter-name>
        <filter-class>com.example.webapp.filter.LoginFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>Login Filter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>
    ...
</web-app>

Note:
If you are using a Web Container or Application Server that supports Servlet version 3.0 and higher then you can annotate your filter class with @WebFilter annotation in which case there is no need to configure the filter in the deployment descriptor (web.xml). See an example of using @WebFilter annotation and more Filter related information here.

Hope this will help you.