Posts tagged ‘Groovy’

Here is a small sample code I wrote that shows object serialization in groovy. when I ran this directly in groovy shell it did not work off the bat. I had to move the class Name to separate file Name.groovy and make sure it is in the class-path to work. Here is the link to original discussion on groovy forum.

// put this in a file named Name.groovy and compile using groovyc 
class Name implements Serializable  {
   def fname, lname
}
// Now run the code below to see the Object serialization and de-serialization.
def test1= new Name(fname: "fn1", lname : "ln1")
def test2 = new Name(fname: "fn2", lname: "ln2")
//serialization
new File("C:/config.txt").withObjectOutputStream { out ->
    out << test1
    out << test2
}
//de-serialization
new File("C:/config.txt").withObjectInputStream { instream ->
    instream.eachObject { 
        println it
    }
}

Posted by satish on January 31, 2009 at 1:25 pm under Groovy, dynamic languages.
Tags: ,
4 Comments.

All controller actions in grails magically have access to request, params, session and bunch of other utility methods such as redirect, render etc. I digged through the grails source to find how it is done. The functionality is added to controller meta-classes utilizing groovy’s meta-programming capabilities. It is written as a plugin where in all the controller meta-classes are attached the functionality we all see. Here is the portion of code that adds some functionality. Imagine writing an action/controller in conventional j2ee style, this small portion of elegant code gets rid of all the boiler plate repetitive code. This simple example shows the power of meta programming. Kudos to all the contributors for this excellent project.

/*
The method below is called for controller meta classes. and RCH is the RequestContenxtHolder from spring MVC
import org.springframework.web.context.request.RequestContextHolder as RCH
*/
def registerCommonWebProperties(MetaClass mc, GrailsApplication application) {
        def paramsObject = {->
            RCH.currentRequestAttributes().params
        }
        def flashObject = {->
            RCH.currentRequestAttributes().flashScope
        }
        def sessionObject = {->
            RCH.currentRequestAttributes().session
        }
        def requestObject = {->
            RCH.currentRequestAttributes().currentRequest
        }
        def responseObject = {->
            RCH.currentRequestAttributes().currentResponse
        }
        def servletContextObject = {->
            RCH.currentRequestAttributes().servletContext
        }
        def grailsAttrsObject = {->
            RCH.currentRequestAttributes().attributes
        }
        // the params object
        mc.getParams = paramsObject
        // the flash object
        mc.getFlash = flashObject
        // the session object
        mc.getSession = sessionObject
        // the request object
        mc.getRequest = requestObject
        // the servlet context
        mc.getServletContext = servletContextObject
        // the response object
        mc.getResponse = responseObject
        // The GrailsApplicationAttributes object
        mc.getGrailsAttributes = grailsAttrsObject
        // The GrailsApplication object
        mc.getGrailsApplication = {-> RCH.currentRequestAttributes().attributes.grailsApplication }
        mc.getActionName = {->
            RCH.currentRequestAttributes().actionName
        }
        mc.getControllerName = {->
            RCH.currentRequestAttributes().controllerName
        }
    }
}

Posted by satish on January 3, 2009 at 10:00 pm under Grails, Groovy, meta programming.
Tags: , ,
2 Comments.