I'd like to expose the backend as 'Resources' (like Restlet) and eliminate the Service Layer so a Rest Resource can direclty interact with a Dao. This way the Resource is the contract and not the Interface.
Is there a problem using #Transactional semantics on a Spring MVC 3 Controller if the transactions are managed locally by Spring? Any gotchas with Rollback and catching exceptions?
#RequestMapping(value = "/user/{userId}", method = RequestMethod.PUT)
#ResponseStatus(HttpStatus.OK)
#Transactional
public void updateUser(#PathVariable Long userId, #RequestBody ProfileUser user) {
// dao update
}
spring config:
<tx:annotation-driven />
<bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
I think you could run into issues here. By default Spring will use a JDK dynamic proxy to apply the transactional behaviour to your method. This relies on your controller implementing a suitable interface i.e. one which exposes an updateUser method. There is an excellent blog post on the Spring blog.
It is likely that you'll see an error due to Spring failing to find the method on the proxy.
You can use your above approach if you tell Spring to use CGLIB based proxies. This is described in the documentation here.
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.
If i write a simple servlet application, in my servlet class i extend the http servlet. This lets the container know that my class is a servlet and it will manage the 'lifecycle' of the servlet. init, doget(), destroy() etc.
But the Spring MVC framweork controller class does not extend any servlet class. it is jsut a POJO with it s own custom methods. Now I can call those methods individually using Requestmapping.
But will this spring controller class be 'mananged' by the container in a same way a servlet lifecyle is managed?
But will this spring controller class be 'mananged' by the container
in a same way a servlet lifecyle is managed?
Not directly. Then entry point of a Spring MVC application is typically a DispatcherServlet*. This class extends (not directly, but through inheritance) HttpServlet. You declare it as you would any other Servlet, typically in web.xml.
However you don't declare it by itself. You provide a Spring ApplicationContext from which the DispatcherServlet can go and get the #Controller annotated classes it will use to handle requests.
The DispatcherServlet handler stack is pretty big. There are many components involved. The official Spring MVC is an excellent document. You should read it.
*I say typically because Spring provides other handlers, HttpRequestHandler for example.
Additional Reading:
Spring MVC and Servlets 3.0 - Do you still need web.xml?
What happens behind the scenes of deploying a Spring MVC application to tomcat outside of eclipse?
What's the difference between #Component, #Repository & #Service annotations in Spring?
Spring MVC: difference between <context:component-scan> and <annotation-driven /> tags?
Difference between <context:annotation-config> vs <context:component-scan>
ContextLoadListener and DispatcherServlet
I am using Spring-MVC LightCouch and CouchDB and I have custom Views that need to be inserted into the DB on deployment. I have found the LightCouch has a method for pulling documents "from desk" as noted on their website:
DesignDocument designDoc = dbClient.design().getFromDesk("example");
Response response = dbClient.design().synchronizeWithDb(designDoc);
This Works good from within JAVA code, however I need to be able to do it in the Spring ApplicationContext.xml I have more than one so I would like to mimick the call of:
dbClient.dessign().synchronizeAllWithDB()
How would I do this in the bean definition of the ApplicationContext I already have this:
<bean id="dbClient" class="org.lightcouch.CouchDbClient" lazy-init="false" destroy- method="shutdown">
<constructor-arg value="couchdb.properties" />
</bean>
It seems you can't do it with Spring xml config, as the init method falls under a different instance; that is returned by the call to design() factory method. Maybe you can try Java code equivalence, i.e. #PostConstruct.
I ended up having to make a bean that synchronized the database on init and created that when the app starts
This feels like a basic question, but I haven't had much luck Googling.
My app connects to an SMTP server and sends mail through it. I need this SMTP server to be configurable based on which environment the app is deployed to.
How can I specify the specify the SMTP server name in my web.xml config file and access it from my Spring MVC 3.0 controller?
The controller does not extend or implement anything. It is completely annotation driven with #Controller and #RequestMapping. From what I have seen online, people access context-params via the servlet API. Being annotation driven, I do not have access to the servlet object.
I solved this.
Make your controller implement ServletContextAware, which requires a method called
setServletContext(ServletContext servletContext)
Spring MVC will inject the servlet context into this method if your controller is ServletContextAware.
Create a private variable on your controller to store the servletController that is injected into the above method. You can now use servletContext just as you would if you were using a regular servlet.
hth.
Adding an instance of Servletcontext and autowiring it worked for me
#Controller
public MyController {
// other instances relevant to your requirement
#Autowired
private ServletContext sCtx;
//other methods relevant to your requirement
}
I suppose following also should work:
void action(final HttpServletRequest request) {
final paramValue = request.getSession().getServletContext().getInitParameter("paramName");
...
}
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.