how to conditionally show jsp content to logged in users with Spring security

How 'bout this? - Spring 2.5 compliant ;-)

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8" %>
<%@ taglib prefix="security" uri="http://www.springframework.org/security/tags" %>

<security:authorize ifAllGranted="ROLE_USER">
   Welcome <%= request.getUserPrincipal().getName() %>
   <a href="<c:url value="/j_spring_security_logout"/>">Logout</a><br/>
</security:authorize>

I've had success with the following:

    <sec:authorize ifAnyGranted="ROLE_ANONYMOUS">
        <td><a href="<c:url value="/login.htm"/>">Login</a></td>
    </sec:authorize>
    <sec:authorize ifNotGranted="ROLE_ANONYMOUS">
        <td><a href="<c:url value="/j_spring_security_logout"/>">Logout</a></td>
    </sec:authorize>

New roles can be added without affecting the logic here.

---

To bring this answer up to date with Spring Security 3, using the isAnonymous() and isAuthenticated() expressions have worked well in combination thus far to achieve the same thing. Here's an example:

<sec:authorize access="isAnonymous()">
    <form method="POST" action="<c:url value='j_spring_security_check'/>">
        Username: <input name="j_username" type="text" value="${SPRING_SECURITY_LAST_USERNAME}" /> 
        Password: <input name="j_password" type="password" /> 
        <input type="submit" value="Sign in" />
    </form>
</sec:authorize>
<sec:authorize access="isAuthenticated()">
    <a href="<c:url value="/j_spring_security_logout" />">Logout</a>
</sec:authorize>

You can use Spring EL in the tag <sec:authorize />, like this:

<%@ taglib prefix="sec" uri="http://www.springframework.org/security/tags" %>

<sec:authorize access="isAuthenticated()">
   YES, you are logged in!
</sec:authorize>

The current version (3.1 perhaps even earlier) supports var parameters for saving the result into an attribute. By that you can code the following:

<sec:authorize var="loggedIn" access="isAuthenticated()" />
<c:choose>
    <c:when test="${loggedIn}">
        You are logged in
    </c:when>
    <c:otherwise>
        You are logged out
    </c:otherwise>
</c:choose>