I'm getting in my project inject (# Inject) CDI Beans scopes Request and Session in a servlet. The problem is that for session beans CDI I'm not getting that states remain. I try to modify the state of the bean from my servlet but when I try to recover from a page is as if the servlet had failed to change state.
Someone could help me?
Hard to help you with so few information. Could you post code and configuration ?
Regarding CDI and Servlet, you also should have a look to Seam Servlet module, it could help you to achieve tour needs differently
Related
In a raw Spring WebSocket application (not using sockjs/STOMP or any other middleware), how can I have Spring inject beans that have been registered in the HTTP session scope so that they can be used by code in my WebSocketHandler bean?
Note that what I am not asking is any of these questions:
How do I create beans in a scope that is accessible to all handler invocations for the same WebSocket session (e.g. as described in the answer to Request or Session scope in Spring Websocket). The beans I need to access already exist in the scope for the HTTP session
How do I (programatically) access objects in the servlet container's HTTP session storage (I haven't tried to do this, but I'm pretty sure the answer involves using an HttpSessionHandshakeInterceptor), but that doesn't get me injection of Spring scoped dependencies.
How to use a ScopedProxy to pass beans between code in different scopes (e.g. as described here); I'm already familiar with how to do this, but attempting to do so for a WebSocketHandler causes an error because the session scope hasn't been bound to the thread at the point the object is accessed.
How to access the current security principal -- again, very useful, but not what I'm currently trying to achieve.
What I'm hoping to do is provide a simple framework that allows for the traditional HTTP-request initiated parts of an MVC application to communicate directly with a WebSocket protocol (for sending simple push updates to the client). What I want to be able to do is push data into a session scoped object from the MVC controller and pull it out in the websocket handler. I would like the simplest possible API for this from the MVC controller's perspective, which if it is possible to just use a session-scoped bean for this would be ideal. If you have any other ideas about very simple ways of sharing this data, I'd also like to hear those in case this approach isn't possible.
You can also use Java API for websocket. This link https://spring.io/blog/2013/05/23/spring-framework-4-0-m1-websocket-support
explains how to do this with Spring.
Ufortunately, something like this
#ServerEndpoint(value = "/sample", configurator = SpringConfigurator.class)
public class SampleEndpoint {
private SessionScopedBean sessionScopedBean;
#Autowired
public SampleEndpoint(SessionScopedBean sessionScopedBean) {
this.sessionScopedBean = sessionScopedBean;
}
}
causes exception (because we're trying to access bean outside its scope), but for singleton and prototype beans it works well.
To work with session attributes you can modify the hanshake and pass required attributes:
public class CustomWebSocketConfigurator extends SpringConfigurator {
#Override
public void modifyHandshake(ServerEndpointConfig config,
HandshakeRequest request,
HandshakeResponse response) {
//put attributes from http session to websocket session
HttpSession httpSession = (HttpSession) request.getHttpSession();
config.getUserProperties().put("some_attribute",
httpSession.getAttribute("some_attribute_in_http_session"));
}
}
P. S. More a comment than an answer. I just wanted to add another way of handling session attributes in websocket to your question-answer. I have been searching the web for exactly the same issue and the way showed above seems to me the most systematic approach to handling the session data in websocket.
I'm getting the following error in Spring OAuth2:
javax.servlet.ServletException: Could not resolve view with name 'forward:/oauth/confirm_access' in servlet with name 'dispatcherServlet'
at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1237) ~[spring-webmvc-4.3.2.RELEASE.jar:4.3.2.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1037) ~[spring-webmvc-4.3.2.RELEASE.jar:4.3.2.RELEASE]
By debugging in Spring impelmentation I noticed that it is hardcoded this view name. Shouldn't it be implemented in Spring? I suppose I shall not build that view and is just a matter of configuration.
My OAuth2 authorization server and resource servers are properly configured, so I skiped that part.
Is there a configuration that handles this view?
Thanks.
P.S I am using Postman client to generate token.
I just found the problem.
The client should have autoApprove flag set on true.
As most people, I have a root and servlet contexts. I need to enable websocket Stomp. I also need to send messages from the Service layer. So how do I configure?
If I put websocket:message-broker into the servlet config, then SimpMessagingTemplate is not autowired in the service layer. If I put it into the root, then it doesn't work at all, it isn't registered as an HTTP handler (even though logs say it does). If I put everything into the dispatcher context, then there is a
java.lang.IllegalStateException: No WebApplicationContext found: no ContextLoaderListener registered?
org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:252
For now I am going to work around it by calling SimpMessaging from Controller, and not Service, but I'd rather a better solution.
I have a spring mvc application which make massive use of beans which are defined in a
request scope. Now I have to use a part of this application outside of this scope (in a
qwertz job in the Magnolia CMS). This doesn't work of course:
Error creating bean with name 'requestHelper': Scope 'request' is
not active for the current thread
I can't change the scope of the beans and I can't change the code. So my only possibility
seems to change the scope of the current thread to a request scope mockup.
I tried something like
XmlWebApplicationContext context = (XmlWebApplicationContext) ApplicationContextProvider.getApplicationContext() ;
MockServletContext mockServletContext = new MockServletContext("/");
context.setServletContext(mockServletContext);
context.refresh();
But this still doesn't activate the request scope in the current thread. How can I achieve
this?
Request scope can be activated as follows:
RequestContextHolder.setRequestAttributes(
new ServletRequestAttributes(new MockHttpServletRequest()));
...
((ServletRequestAttributes) RequestContextHolder.getRequestAttributes())
.requestCompleted();
RequestContextHolder.resetRequestAttributes();
Thoguh I think it's not a good idea to use such a hack in production code.
It seems natural that a HttpServlet running in OSGi environment (i.e. registered in OSGi HttpService) would want to call some OSGi services to accomplish it's tasks. The question is how to obtain references to these OSGi service inside the servlet.
One way would be to inject dependencies into the HttpServlet instance that is being registered to the OSGi HttpService like this:
MyServlet servlet = new MyServlet();
servlet.setFooService(fooService);
httpService.registerServlet("/myservlet", servlet, initparams, context);
I'm not sure if this is a valid approach since in non-OSGi environment the servlet life-cycle is managed by the Web Container and hence the service reference would not be injected for the servlet instances created later on.
There is another way to solve this when using PAX Web as an implementation of the OSGi HttpService. PAX Web exports the OSGi BundleContext into the ServletContext as a special attribute "osgi-bundlecontext". The BundleContext can then be used to obtain necessary service references:
public void init(ServletConfig servletConfig) throws ServletException {
ServletContext context = servletConfig.getServletContext()
BundleContext bundleContext =
(BundleContext) context.getAttribute("osgi-bundlecontext");
ServiceReference serviceRef =
bundleContext.getServiceReference("com.foo.FooService")
}
However this approach is rather ugly and ties you to a concrete implementation of the OSGi HttpService. Do you know any other (and possibly better) solution to this problem?
If you use a setter for the dependency on the service, as you have shown, it can work outside of OSGi as well. You just need to use some other dependency injection mechanism. If there is none, you could provide a subclass that initializes the servlet using JNDI lookups or from the servlet context.
public class MyServlet_AdapterForMissingDI extends MyServlet{
public void init(ServletConfig config){
setFooService(getItFromSomewhere());
}
}
The point being that if you have DI capabilities that can inject setFooService, you can just use the same servlet in OSGi and elsewhere, if you do not (and still want to support this case), you provide an adapter.
On a related note, check out Felix SCR to configure your object's dependencies, and Pax Web Extender Whiteboard, which takes care of hooking your servlet up with the HttpService.
Specifically, without SCR and Whiteboard, you need to think about the case when the fooService becomes unavailable later, or the HttpService gets started after your servlet.
In these cases your servlet would have a reference to a dead service that prevents the bundle from being garbage-collected, or your servlet would not be registered with the HttpService.
Update: Here is the SCR descriptor I use for one of my servlets. SCR handles servlet instantiation, life-cycle, registration (via Whiteboard), and dependencies. There is no OSGi-specific code in the servlet. There is not even the need for a BundleActivator anymore (SCR registers all services):
<component name="oracle.statusServlet" >
<implementation class="mypackage.DataSourceStatusServlet"/>
<property name="service.description" value="Oracle DataSource status servlet" />
<property name="alias" value="/OracleDataSourceStatus" />
<property name="servlet-name" value="Oracle DataSource status servlet" />
<service>
<provide interface="javax.servlet.Servlet" />
</service>
<reference name="DATASOURCES"
interface="javax.sql.DataSource"
cardinality="0..n" policy="dynamic"
bind="bindDataSource" unbind="unbindDataSource"/>
</component>
The dependencies for the servlet are specified in the reference tag. SCR will do the service lookup and binding.
May be an old post and you already might have got the answer..
Are you launching felix or whatever OSGi container yourself. If that is the case you can set the bundle context as an attribute to the servlet context.
Whats wrong in using an http service by PAX. ultimately the thread management and other aspects are taken care of by the servlet container in which you run this http service.
You could inject the services into some object, which is then queried by the servlets.