Spring MVC - Convention over Configuration w/o Confusion?

Convention over configuration is an essential feature of Spring MVC and it does save some unnecessary coding effort, but I have more than one case where it can get really messy debugging issues.
Here is a simple example: URL app/contact - worked before invoking list method as the only GET method w/o any method level mapping - catch all after the controller mapping.

Beginning 3.1 it will not & throws a 404. But app/contact/list works & will invoke this GET method (IRRESPECTIVE OF THE METHOD NAME), as long it is the only catch-all GET method.

So you could even name it as fooBar and the same URL will invoke it. If however you get confident that the catch-all GET method will always be called for the GET and the URL won't matter, you are right but then the RequestToViewNameMapping goes out the window for the desired view; instead it will look for foorBar.jsp
Something to watch out for!

@Controller
@RequestMapping("contact")
public class ContactController{

@RequestMapping(method = RequestMethod.GET)
 public List<contact> list() {
  logger.info("default method list");
  return contactService.list();
 }
}

Note the mapping generated for this method: INFO : org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping - Mapped "{[/contact/*],methods=[GET],params=[],headers=[],consumes=[],produces=[],custom=[]}" onto public java.util.List com.aj.recipes.web.ContactController.list()

Spring Converter/ConversionService Example

Spring MVC provides so many cool features to make the controller code as minimal as possible. Converter & the ConversionService is one such feature that will be invoked by the framework to carry out type conversions. I have been looking for a decent example & stackoverflow came to the rescue.

I want to add some more information to the solution. As per the Spring documentation here a URI template variable gets translated to the target object using the Converter/ConversionService. I tried to use a `@RequestParam("id") @ModelAttribute("contact") Contact contact`, but I was getting an `IllegalStateException: Neither BindingResult nor plain target object for bean name 'contact' available as request attribute` for not having the model object `contact` in my view edit.jsp. This can be easily resolved by declaring a `Model model` and `model.addAttribute(contact);`. However, there is an even better way; using the URI template variable. It's strange why `@RequestParam` did not work. DID NOT WORK

    @RequestMapping("edit") //Passing id as .. edit?id=1
 public String editWithConverter(@RequestParam("id") @ModelAttribute("contact") Contact contact){
  logger.info("edit with converter");
   return "contact/edit";
 }

WHAT WORKED

    @RequestMapping("edit/{contact}") //Passing id as .. edit/1
 public String editWithConverter(@PathVariable("contact") @ModelAttribute("contact") Contact contact){ // STS gave a warning for using {contact} without @PathVariable 
  logger.info("edit with converter");
   return "contact/edit";
 }

So what does this thing do
.. a link like `...edit/1` implicitly invokes the converter for String '1' to Contact of id '1' conversion, and brings this contact object to the view. No need for `@InitBinder` and since its a `Converter` registered with the `ConversionService` I can use this **anywhere I want - implicitly or explicitly**.

Converter:

public class StringToContactConverter implements Converter <String, Contact > {
 private static final Logger logger = LoggerFactory
   .getLogger(StringToContactConverter.class);
 @Autowired
 private ContactService contactService;
 public void setContactService(ContactService contactService) {
  this.contactService = contactService;
 }
 @Override
 public Contact convert(String id) {
  logger.info("Converting String to Contact");
  Contact contact = contactService.getContact(Long.parseLong(id));
  return contact;
 }
}

Configuration: servlet-context.xml

<annotation-driven conversion-service="conversionService"/>

<beans:bean id="conversionService" class="org.springframework.context.support.ConversionServiceFactoryBean" >
<beans:property name="converters">
<beans:list>
<beans:bean class="com.aj.recipes.web.convert.StringToContactConverter">
</beans:bean></beans:list>
</beans:property>
</beans:bean>