Refreshing model data on tab change event - primefaces

Question

I'm using primefaces tabView component. Each tag has its own managed bean and .xhtml page referencing that bean.
The problem is that EACH TIME tab is clicked, fresh data should be fetched from database (not just the first time), in other words data should be refreshed.
My beans are #ViewScoped. I don't want to use #RequestScoped because I have very dynamic ajax-enabled pages.
My solution currently looks like this:
I have managed bean for the main page with tabView component (MainBean) which contains method for handling tabChange event.
That bean also has references to beans assigned to each tab (TabBean1, TabBean2) so that right bean could be refreshed according to the id of the chosen tab.
MainBean:
#ManagedBean(name = "mainBean")
#ViewScoped
public class MainBean implements Serializable {
private static final long serialVersionUID = 1L;
#ManagedProperty(value = "#{tabBean1}")
private TabBean1 tabBean1;
#ManagedProperty(value = "#{tabBean2}")
private TabBean2 tabBean2;
public void onTabChange(TabChangeEvent event) {
String id = event.getTab().getId();
if ("tab1Id".equals(id)) {
tabBean1.init();
} else if ("tab2Id".equals(id)) {
tabBean2.init();
}
}
public TabBean1 getTabBean1() {
return tabBean1;
}
public void setTabBean1(TabBean1 tabBean1) {
this.tabBean1 = tabBean1;
}
public TabBean2 getTabBean2() {
return tabBean2;
}
public void setTabBean2(TabBean2 tabBean2) {
this.tabBean2 = tabBean2;
}
}
TabBean1:
#ManagedBean(name = "tabBean1")
#ViewScoped
public class TabBean1 implements Serializable {
private static final long serialVersionUID = 1L;
private List<String> data;
#PostConstruct
public void init() {
// refresh data
}
}
TabBean2:
#ManagedBean(name = "tabBean2")
#ViewScoped
public class TabBean2 implements Serializable {
private static final long serialVersionUID = 1L;
private List<String> data;
#PostConstruct
public void init() {
// refresh data
}
}
Relevant part od main.xhtml:
<p:tabView id="tabViewID" cache="false" dynamic="true">
<p:ajax event="tabChange" listener="#{mainBean.onTabChange}" />
<p:tab title="Tab 1" id="tab1Id">
<ui:include src="tab1Page.xhtml" />
</p:tab>
<p:tab title="Tab 2" id="tab2Id">
<ui:include src="tab2Page.xhtml" />
</p:tab>
</p:tabView>
Problem with this approach is:
when MainBean is constructed, all its managed properties are constructed also. This is a huge problem because #PostConstruct method of each bean fetches some data from database and everything is just too slow beacuse all beans are initialized when only one should really be initialized (the one assigned to selected tab)
on first page load, init() method is called twice for TabBean1, once because of #PostConstruct and once because it is assigned to tabChange event (first tab is selected by default)
My question is:
how can I 'refresh bean data' when corresponding tab is clicked?
how can I do that dynamically, just for the chosen tab (initially and every click after)?
I would really appreciate your suggestions. Thanks!
I'm using Primefaces 6.0, JSF 2.2.