Hello

Below code will help you to implement change password from custom portlet.

Please follow below steps :

step 1 : create Action URL

<portlet:actionURL name="updatePassword" var="updatePassword"/>

step 2 : Write below code in JSP page

<aui:form method="post" action="<%=updatePassword%>" name="updatepassword" id="updatepassword">    
        <aui:input label="" name="current" type="text"></aui:input>
        <aui:input label="" name="password1" type="text"></aui:input>
        <aui:input label="" name="password2" type="text"></aui:input>
        <aui:button type="submit" label="" value="Save"></aui:button>
        </aui:form> 

step 3 : Write below Action Class

public void updatePassword(ActionRequest actionRequest, ActionResponse actionResponse) throws IOException
        {
            ThemeDisplay themeDisplay = (ThemeDisplay) actionRequest.getAttribute(WebKeys.THEME_DISPLAY);
            UploadPortletRequest uploadRequest = PortalUtil.getUploadPortletRequest(actionRequest);
            String current =uploadRequest.getParameter(actionResponse.getNamespace()+"current");
            String password1 =uploadRequest.getParameter(actionResponse.getNamespace()+"password1");
            String password2 =uploadRequest.getParameter(actionResponse.getNamespace()+"password2");
            logger.info(current+"   "+password1+"   "+password2);
            try {
                long userId=UserLocalServiceUtil.authenticateForBasic(themeDisplay.getCompanyId(), "emailAddress", themeDisplay.getUser().getEmailAddress(), current);
                if(themeDisplay.getUserId()!=userId)
                {
                    throw new Exception("Invalid current password.");
                }
                if(!password1.equals(password2))
                {
                    throw new Exception("Please confirm new password.");
                }
                UserLocalServiceUtil.updatePassword(userId, password1, password2, false);

            } catch (PortalException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (SystemException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            catch (Exception e) {
            // TODO Auto-generated catch block
                System.out.println(e.getMessage());
        }

        }