What is the minimal configuration for REST-fully annotated service built on Spring 3 (m3)?

Question

I'm trying to expose a REST-full service (hosted by Tomcat) and can't figure out what is the required configuration for Spring 3 (M3).

This is how (example) the service looks like:

@Controller
@Scope("prototype")
public class UsersController
{
    @RequestMapping(value="/users/hello", method=RequestMethod.GET)
    public String hello()
    {
     return "hello, user!";
    }
}

The Spring configuration that I have looks like this (I omit the full class names for simplicity):

<beans ...>
    <context:annotation-config />
    <bean class="...AutowiredAnnotationBeanPostProcessor"/>
    <bean class="...DefaultAnnotationHandlerMapping">
    <context:component-scan base-package="com.mycompany.myserver"/>
</beans>

This is how I've plugged-in my Spring configuration into web.xml:

    <listener>
            <listener-class>...RequestContextListener</listener-class>
    </listener>
    <!-- Servlets -->
    <servlet>
     <servlet-name>dispatcher</servlet-name>
     <servlet-class>...DispatcherServlet</servlet-class>
     <init-param>
      <param-name>contextConfigLocation</param-name>
      <param-value>classpath:*:dispatcher-servlet.xml</param-value>  
     </init-param>
     <load-on-startup>2</load-on-startup>
    </servlet>
    <servlet-mapping>
     <servlet-name>dispatcher</servlet-name>
     <url-pattern>/services/*</url-pattern>
    </servlet-mapping>

Note that I'm trying to create a minimal configuration (no extra servlet-config.xml files). This is why I'm pointing the Dispatcher to a built-in configuration.

Is this correct?

After I start Tomcat and all the beans are loaded I'm navigating to the following URL:

http://localhost:8080/myserver/services/users/hello

And, instead of the "hello, user!" reply, to my dismay, I see the following errors in the log file:

09:54:45,140 DEBUG RequestContextListener:69 - Bound request context to thread: org.apache.catalina.connector.RequestFacade@19299f5
09:54:45,140 DEBUG DispatcherServlet:834 - DispatcherServlet with name 'dispatcher' determining Last-Modified value for [/myserver/services/users/hello]
09:54:45,156 DEBUG DefaultAnnotationHandlerMapping:178 - Mapping [/users/hello] to handler 'com.symantec.repserver.myserver.UsersController@21447f'
09:54:45,171 DEBUG DispatcherServlet:850 - Last-Modified value for [/myserver/services/users/hello] is: -1
09:54:45,171 DEBUG DispatcherServlet:683 - DispatcherServlet with name 'dispatcher' processing GET request for [/myserver/services/users/hello]
09:54:45,218 DEBUG HandlerMethodInvoker:148 - Invoking request handler method: public java.lang.String com.symantec.repserver.myserver.UsersController.hello()
09:54:45,218 DEBUG DefaultListableBeanFactory:1366 - Invoking afterPropertiesSet() on bean with name 'hello, user!'
09:54:45,218 DEBUG DispatcherServlet:1060 - Rendering view [org.springframework.web.servlet.view.InternalResourceView: name 'hello, user!'; URL [hello, user!]] in DispatcherServlet with name 'dispatcher'
09:54:45,234 DEBUG InternalResourceView:237 - Forwarding to resource [hello, user!] in InternalResourceView 'hello, user!'
09:54:45,250 DEBUG DispatcherServlet:834 - DispatcherServlet with name 'dispatcher' determining Last-Modified value for [/myserver/services/users/hello, user!]
09:54:45,250 DEBUG DispatcherServlet:842 - No handler found in getLastModified
09:54:45,250 DEBUG DispatcherServlet:683 - DispatcherServlet with name 'dispatcher' processing GET request for [/myserver/services/users/hello, user!]
09:54:45,250  WARN PageNotFound:959 - No mapping found for HTTP request with URI [/myserver/services/users/hello, user!] in DispatcherServlet with name 'dispatcher'
09:54:45,250 DEBUG DispatcherServlet:643 - Successfully completed request
09:54:45,250 DEBUG DispatcherServlet:643 - Successfully completed request
09:54:45,250 DEBUG RequestContextListener:89 - Cleared thread-bound request context: org.apache.catalina.connector.RequestFacade@19299f5

As you notice, my current configuration is trying to reroute this request as a new request:

/myserver/services/users/hello, user!

Any idea what is wrong? What am I missing?

Answer 1

The issue is your hello() method is annotated as a handlerMethod to Spring and per the @RequestMapping documentation, handler methods may return any number of objects but if it returns a String then :

@Request Documentation

A String value which is interpreted as view name, with the model implicitly determined through command objects and ModelAttribute annotated reference data accessor methods. The handler method may also programmatically enrich the model by declaring a ModelMap argument (see above)

So it's basically looking for the mapping for that String you return 'hello, user' - which doesn't exist. You may have your method return void and inside the method write out to the HttpServletResponse yourself.

Further answer:

@RequestMapping(value="/users/hello", method=RequestMethod.GET) 
public void hello(Writer w) { 
   w.write("hello, user!"); 
   w.flush(); 
   return; 
}

You may want to get the entire HttpServletResponse rather then just the Writer, that way you can set the appropriate Http Headers.

Sorry my comment below is jumbled, I'm new to this site.