Grails get Session and Management in Service class

Question

I have a problem with Grails Session. I was thinking about having a Service Class for my session handling. So I created a class called "SessionService" (under grails-app/services/grails/).

class SessionService {
    static transactional = true
    GrailsWebRequest request = RequestContextHolder.currentRequestAttributes()
    GrailsHttpSession session = request.session

    def setTestvar(String value) {
        if (session != null)
            session.setAttribute("sTeststring", value)
    }

    def getTestvar() {
        if (session != null)
            session.getAttribute("sTeststring")
    }
}

The Problem is now, that I get a Nullpointer-Exception: "Method threw 'java.lang.NullPointerException' exception. Cannot evaluate org.codehaus.groovy.grails.web.servlet.mvc.GrailsHttpSession.ToString()".

Usage of my Service Class e.g. in a Controller:

class SampleController {

    SessionService sessionService

    def selectAnything = {

        sessionService.setTestvar("test-value")
        render(view: "testview")
    }
}

What am I'm doing wrong here? Is it the right way? Or do I have to set "session = request.session" in every method?

Hope to get help from you.

Thank you very much in advance.

Cheers,

Marco

Solution 1

where does RequestContextHolder come from? Its not visible in grails 3.3.8 (in plugin at least)

Solution 2

Here is some sample code where I'm pulling session data and request data from a service without passing the request or session objects as a parameter to the service.

package beecomplete

import org.codehaus.groovy.grails.web.util.WebUtils

class HelperService {

    public User getCurrentUser() {
        def webUtils = WebUtils.retrieveGrailsWebRequest()
        return User.findById(webUtils.getSession().userid)
    }

    public Object getModelAttribute(String key) {

        def webUtils = WebUtils.retrieveGrailsWebRequest()
        return webUtils.getCurrentRequest().getAttribute(key)
    }
}

Solution 3

For new versions (>2.2) of Grails:

import org.codehaus.groovy.grails.web.util.WebUtils

....
HttpServletRequest request = WebUtils.retrieveGrailsWebRequest().currentRequest
HttpSession session = request.session

Comments

[grailsInvas0r]

Hey Christian, thanks. But there's no "getSession()"-method available on currentRequestAttributes. Doing "Session manipulation(setting/getting)" directly can be error-prone, I want to avoid it an keep session variable naming and handling in one place ;-)

[user852518]

How did you check that getSession() ist not available? I tried the code in a grails console and it worked.

[grailsInvas0r]

Oh I have to apologize, it works. BUT my IntelliJ underlines it that this method doesn't exist :-O Also in every documentation it's not available. Only OLD google results shows this solution. I'm not sure if this works in future?! I'm surprised :-O My solution was now: ServletRequestAttributes servletRequestAttributes = (ServletRequestAttributes) RequestContextHolder.currentRequestAttributes(); return servletRequestAttributes.getRequest().getSession(true);

[Burt Beckwith]

It's not in the interface, but it's in the Grails implementation class, so it's not clear to the IDE that it's available but it is, and is safe to use.

[tzrlk]

WebUtils.retrieveGrailsWebRequest().session is a wonderfully elegant solution.

[Mauro]

Great! How do you discover WebUtils class?

[demon101]

in new version of grails WebUtils has been implemented. see my answer stackoverflow.com/questions/7062605/…

[John Little]

import org.codehaus.groovy.grails.web.util.WebUtils not found for grails 3.3?

[John Little]

Hi, where do you get RequestContextHolder from? Intellij cant find it, or where to import it from.

[Don Cruickshank]

@JohnLittle Hi John - I think something went wrong when you wrote the comment and it edited the actual answer!