The right way is the one already suggested by AleksandrM in comments: open the page, show an indicator while you call an ajax action (let's say with jQuery, for convenience), then render the result and remove the indicator. It's easier than you think:
public class MainAction extends ActionSupport {
public String execute() {
return SUCCESS;
}
}
public class AjaxAction extends ActionSupport {
@Autowired
private ServiceDelegate myService;
private Stuff myStuff; // with getter
public String execute() {
myStuff = myService.loadLongStuff();
return SUCCESS;
}
}
Your AJAX action can either return JSON data, a JSP snippet or a Stream of binary data. Choose the way you prefer. For example, if you map SUCCESS of AjaxAction to a JSP snippet, your JSP snippet will be:
ajaxSnippet.jsp
<%@ taglib prefix="s" uri="/WEB-INF/struts-tags.tld" %>
Stuff: <s:property value="myStuff" />
Then in your main.jsp, show the indicator in the div you will overwrite with the AJAX call's result:
main.jsp
<body>
<div id="main">
<img src="/images/mesmerizingProgressBar.gif" />
</div>
<script>
$(function(){ // onDocumentReady...
$.ajax({ // call ajax action...
type : 'GET',
url : '/ajaxAction.action',
success : function(data,textStatus,jqXHR){
// then render your result in "main" div,
// overwriting the loading GIF
$("#main").html(data);
},
error : function(jqXHR, textStatus, errorThrown){
$("#main").html("Error ! " + textStatus);
}
});
});
</script>
</body>
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