Get the ID of Particular record on click of edit from List View page

Question

I am opening one VF page on click of edit fo lis view of particular object. Now I want to get the id of that particular record which I edited. I am writing this code but its throwing this error.

Cyclical server-side forwards detected: /apex/CasePopulate

VF Code

<apex:page standardController="Case_Accession__c" extensions="ExtentionController1" action="{!pageredir}"  >
<apex:form >
<apex:pageBlock >
 <!-- Begin Default Content REMOVE THIS -->
<h1>Congratulations</h1>
This is your new Page
<!-- End Default Content REMOVE THIS -->
<apex:inputText value="{!TestEditSpecimenID }"/>
</apex:pageBlock>
  </apex:form>
</apex:page>

Apex Code

public class ExtentionController1
{
     public String var {get;set;}
     public string TestEditSpecimenID {get;set;}
 public ExtentionController1(ApexPages.StandardController controller)
 {}
 public Pagereference pageredir()
 {
  var= ApexPages.currentPage().getParameters().get('Id');
       if(var!=null)
       {
         TestEditSpecimenID = var;
         Pagereference newpage = new Pagereference ('/apex/CasePopulate');
          //Pagereference newpage =Page.Accession;
        return newpage;
       }
        else
       {
         //Pagereference newpage =Page.Accession;
         return null;
       }
   }
}

One more thing please I want to show the ID of reord into " "

Thanks in advance Raman

Answer 1

Use with StandardController getId method

var = controller.getId();

Answer 2

Since you're using a controller extension, it takes a reference to a StandardController as the sole parameter in its constructor:

public class ExtentionController1
{
    public String var {get;set;}
    public string TestEditSpecimenID {get;set;}

    public ExtentionController1(ApexPages.StandardController controller)
    {}

You can use that controller to get the record selected by the user. The standard controller for the page specified in the <apex:page> tag is the Case_Accession__c controller, so you can save a reference to the record in a member variable in your class by casting the object returned by the StandardController's getRecord() method:

public class ExtentionController1
{
    public String var {get;set;}
    public string TestEditSpecimenID {get;set;}
    public Case_Accession__c caseAccession {get;set;}

    public ExtentionController1(ApexPages.StandardController controller)
    {
        // the cast
        caseAsccession = (Case_Accession__c)controller.getRecord();
    }

Now you can access the Id using caseAccession.Id or any other field that's being referenced in the Visualforce page (the controller only loads the fields used).