Render属性会再次创建组件还是仅更新模型？

Question

I am trying below code

public String collapseTreeById(ActionEvent event) throws IOException {
     String treeId = FacesContext.getCurrentInstance().getExternalContext().getRequestParameterMap().get("treeId");
     UITree tree = (UITree)event.getComponent().findComponent(treeId);
     tree.getParent().getChildren().clear();

     return null;
 }

Here you can check i already remove all the children of the component and this method called like this

<a4j:commandLink actionListener="#{inventoriesBean.collapseTreeById}"
                             value="collapse" render="treeServType">
 <f:param value="treeServType" name="treeId" />
 </a4j:commandLink>

and also added render but still i am seeing tree is in same state(No change from previous state) and not created again . If render not creating a component again and updating model value then even tree state should be change? Its also not happening.

Why?

Answer 1

Render generates pieces of HTML and sends them to the client, since you've removed the tree it doesn't send back anything. If you want it to work you have to wrap the tree in another component and rerender that component.

On the other hand emptying the list of children doesn't really do anything (and you shouldn't do it), the component tree is recreated with each request.