Executing custom logic in BPM human task

Scenario: Excuting a custom logic in BPM human task before calling the action of BPM services. 
Let us think that we want some custom logic to be executed on click of Approve/Reject button in BPM human task. 

Solution:
To achieve this, we need to follow the below two steps,

Step 1: Write a managed bean and a submit method and write your custom code first and then the below code to invoke the BPM services.

public String submit(){        // Custom Logic goes here.............................         //Invoking BPM Services                     Map map =                         FacesContext.getCurrentInstance().getExternalContext().getRequestMap();                     oracle.bpel.services.workflow.worklist.adf.InvokeActionBean invokeActionBean =                         (oracle.bpel.services.workflow.worklist.adf.InvokeActionBean)map.get("invokeActionBean");                     String result = invokeActionBean.invokeOperation();                      return result;     }

Step 2: Configure this method as action method in the jspx for the Approve/Reject/Ok button.

text="#{wf:getResourceValue('OK', 'bindings.customActions')}"                                                disabled="#{!bindings.OK.enabled}"                                                action="#{pageFlowScope.managedBean.submit}"                                                partialSubmit="false"                                                visible="#{wf:isCustomActionAvailable('OK', 'bindings.customActions')}"                                                id="ctb1">                                                              value="bindings.OK"/>