Saturday, August 23, 2014

How to Inject Objects Into Spring MVC Controller Using HandlerMethodArgumentResolver

This post shows how to implement HandlerMethodArgumentResolver in other to resolve and inject objects into Spring MVC controllers, but before we get to the actual implementation procedure, a little trivial overview of Spring MVC would be good.

Spring MVC is designed around the Front Controller Pattern which it uses to implement the Model View Controller pattern.

Since you are reading this post, I can rightly assume you already use Spring MVC and you know how it generally works: You register the DispatcherServlet -Spring MVC's Front Controller, write your controller class and map requests to controller methods using @RequestMapping, then put the necessary configuration in place which would enable Spring to pick the written controller class and have it as a spring managed bean.

A trivial controller class may look like this:

package com.springapp.mvc;

import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;

public class HelloController {

    public String doGreeting(Model model) {
        model.addAttribute("greet", "Hello World");
        return "helloView";

So when a request hits /index, doGreeting(...) method is invoked with an object of Model (the M in MVC) passed into it, which is populated with the greet property which can then be accessed in whatever view technology in used. The view is located using the "helloView" string returned by the controller.

Tuesday, August 05, 2014

Configuring Maven to Fetch Artifacts from Multiple Repositories

It is quite common to have a situation where a project needs to source for artifacts from more than one source. This post quickly explain 3 different ways to achieve this.

Repositories settings in pom.xml

In pom.xml, you have the <repositories/> tag which can be used to specify the repositories a project should search and download artifacts from. For example: