Spring mvc - implementation of WebArgumentResolver - spring

Question

I wanted to create custom controller method argument annotation.
Following this question How to pass a session attribute as method argument (parameter) with Spring MVC and following #Bozho advice I have something like this:
my resolver
public class SessionAttributeAnnotationResolver implements WebArgumentResolver {
public Object resolveArgument(MethodParameter parameter,
NativeWebRequest request) throws Exception {
System.out.println("I am here");
Annotation[] parameterAnnotations = parameter.getParameterAnnotations();
Class<?> parameterType = parameter.getParameterType();
for (Annotation parameterAnnotation : parameterAnnotations) {
if (SessionAttribute.class.isInstance(parameterAnnotation)) {
SessionAttribute sessionAttribute = (SessionAttribute) parameterAnnotation;
String parameterName = sessionAttribute.value();
boolean required = sessionAttribute.required();
HttpServletRequest httprequest = (HttpServletRequest) request
.getNativeRequest();
HttpSession session = httprequest.getSession(false);
Object result = null;
if (session != null) {
result = session.getAttribute(parameterName);
}
if (result == null && required && session == null)
raiseSessionRequiredException(parameterName, parameterType);
if (result == null && required)
raiseMissingParameterException(parameterName, parameterType);
return result;
}
}
return WebArgumentResolver.UNRESOLVED;
}
protected void raiseMissingParameterException(String paramName,
Class<?> paramType) throws Exception {
throw new IllegalStateException("Missing parameter '" + paramName
+ "' of type [" + paramType.getName() + "]");
}
protected void raiseSessionRequiredException(String paramName,
Class<?> paramType) throws Exception {
throw new HttpSessionRequiredException(
"No HttpSession found for resolving parameter '" + paramName
+ "' of type [" + paramType.getName() + "]");
}
}
the annotation
#Target(ElementType.PARAMETER)
#Retention(RetentionPolicy.RUNTIME)
public #interface SessionAttribute {
String value();
boolean required() default true;
}
simple controller to test everything
#Controller
#RequestMapping("/test")
public class TestController {
#RequestMapping(method= RequestMethod.GET)
public String t(#SessionAttribute("userEntity") UserEntity e2,Model model,HttpServletRequest req){
System.out.println(req.getSession().getId());
UserEntity e=(UserEntity) req.getSession().getAttribute("userEntity");
System.out.println(e.getName());
System.out.println(e2.getName());
return "login";
}
}
and finally, Spring configuration
<beans:bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter">
<beans:property name="customArgumentResolver" ref="sessionAttributeAnnotationResolver"/>
</beans:bean>
<beans:bean id="sessionAttributeAnnotationResolver" class="pl.meble.taboret.utils.SessionAttributeAnnotationResolver"/>
now, everything seems in order to me, but there is probably some silly mistake that I done, because when controller is executed, I am getting
F0B282C93B74F8FA3F21A51F46D4D4D5
username
null

Answer 1

With Spring 3.1.0 the ArgumentResolver has now changed to HandlerMethodArgumentResolver - prior to that it used to be WebArgumentResolver - a related answer is here
Once you have written a new HandlerMethodArgumentResolver which is not very different from your current implementation you can register it this way:
<mvc:annotation-driven>
<mvc:argument-resolvers>
<bean id="sessionAttributeAnnotationResolver" class="..SessionAttributeAnnotationResolver ">
</bean>
</mvc:argument-resolvers>
</mvc:annotation-driven>