Spring current session - how to get a user id - spring

Question

I would like to get the id of the currently logged in user and use it to access their specific user page.
To implement that I have been able to get the current logged in user's name using:
#RequestMapping(value = "/main/home", method = RequestMethod.GET)
public String getHomePage(Model model, Principal principal, HttpServletRequest
request) {
try {
CustomUser customUser =
(CustomUser)SecurityContextHolder.getContext()
.getAuthentication().getPrincipal();
request.getSession().setAttribute("name",
customUser.getName());
request.getSession().setAttribute("userId",
customUser.getUserId());
request.getSession().setAttribute("user", customUser);
} catch (Exception e) {
e.printStackTrace();
}
return "/main/home";
}
Then in the JSP page, I'm using the following code to try to get the user's page based on their id:
<c:url value="/main/user/?userId=${user.userId}" var="url"/><a href="<c:out
value='${url}'/>">User Page</a>
But this implementation is not working. When I click on the user page, I receive the following error:
java.lang.IllegalArgumentException: id to load is required for loading
org.hibernate.event.spi.LoadEvent.<init>(LoadEvent.java:87)
org.hibernate.event.spi.LoadEvent.<init>(LoadEvent.java:59)
org.hibernate.internal.SessionImpl$IdentifierLoadAccessImpl.load(SessionImpl.java:2421)
org.hibernate.internal.SessionImpl.get(SessionImpl.java:974)
com.project.myapp.dao.UserDAO.getUserByID(UserDAO.java:91)
com.project.myapp.dao.UserDAO$$FastClassByCGLIB$$b394c410.invoke(<generated>)
org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:698)
org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:150)
org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:110)
org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:631)
com.project.myapp.dao.UserDAO$$EnhancerByCGLIB$$232ac7e1.getUserByID(<generated>)
com.project.myapp.service.UserServiceImpl.getUserByID(UserServiceImpl.java:54)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
java.lang.reflect.Method.invoke(Method.java:601)
org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:317)
org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:183)
org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:150)
org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:110)
org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:204)
$Proxy314.getUserByID(Unknown Source)
com.project.myapp.controller.UserController.getUserPage(UserController.java:70)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
java.lang.reflect.Method.invoke(Method.java:601)
org.springframework.web.method.support.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:219)
org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:132)
org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:104)
org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:746)
org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:687)
org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:80)
org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:925)
org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:856)
org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:915)
org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:811)
javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:796)
javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
I would like any insight into knowing why I cannot request the user's id but I can get the user's name.