I have the following controller
@Controller
@RequestMapping("/project/view.html")
public class ProjectViewController {
private static final String viewName = "projectView";
@RequestMapping(method = RequestMethod.GET)
public String showPage(Model model,
@RequestParam(value="id",required=false) Long id) {
//code.....
return viewName;
}
}
My views.properties contains
projectView.(class)=org.springframework.web.servlet.view.JstlView
projectView.url=/WEB-INF/jsp/project/view.jsp
Everything works as expected.
But I needed to change the method to return a View(), cause I have to return a RedirectView() to some error page if something fails. So I've changed the method to:
@Controller
@RequestMapping("/project/view.html")
public class ProjectViewController {
private static final String viewName = "projectView";
@RequestMapping(method = RequestMethod.GET)
public View showPage(Model model,
@RequestParam(value="id",required=false) Long id) {
//code.....
return new JstlView(viewName);
}
}
But in this case I get a NPE :
java.lang.NullPointerException
at org.springframework.web.context.support.WebApplicationObjectSupport.getServletContext(WebApplicationObjectSupport.java:121)
at org.springframework.web.servlet.view.JstlView.exposeHelpers(JstlView.java:133)
at org.springframework.web.servlet.view.InternalResourceView.renderMergedOutputModel(InternalResourceView.java:209)
at org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:257)
at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1183)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:902)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:807)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:571)
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:501)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at com.opensymphony.sitemesh.webapp.SiteMeshFilter.obtainContent(SiteMeshFilter.java:129)
at com.opensymphony.sitemesh.webapp.SiteMeshFilter.doFilter(SiteMeshFilter.java:77)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:845)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
at java.lang.Thread.run(Thread.java:619)
I've debugged and it seems that getWebApplicationContext() returns null.
Any help appreciated.
Thanks.
Best Answer
The cause of your exception is that instances of
JstlView
need to be injected with certain things before they can be used, for example the currentWebApplicationContext
. Normally, this is transparent to you, because Spring instantiates and preparesJstlView
for you. It's only when you do it yourself, that you see what's involved.Now, you could call
setApplicationContext
on theJstlView
that you instantiate, but you don't want your controllers getting involved in that sort of thing. You really want to keep Spring doing the work.Now, since you're using
views.properties
, it follows that you're also usingResourceBundleViewResolver
to resolve your views. The trick here is to realise that Spring can handle multiple view resolvers in the same context, it'll simply ask them one after the other, until one of them resolves the view name.So my suggestion would be to add another resolver to your context, this time an
InternalResourceViewResolver
(this is actually the default resolver, but that default is suppressed when you specified yourResourceBundleViewResolver
).Now, when you return a view name that the
ResourceBundleViewResolver
can't resolve, theInternalResourceViewResolver
will be consulted.InternalResourceViewResolver
just takes the view name as the actual JSP path (e.g. return/WEB-INF/page.jsp
directly from your controller method). It also lets you use syntax likeredirect:/path/to/my/url
.So yours other controllers can keep on returning view names as specified in
views.properties
, but now in addition you can return dynamically-assembledredirect:x/y/
view names, which will be translated byInternalResourceViewResolver
into aRedirectView
. No need to construct these views yourself.One last point to note: the view resolvers are consulted in the order in which they appear in the beans file, and
InternalResourceViewResolver
must come last in that list.