No default constructor found; nested exception is java.lang.NoSuchMethodException with Spring MVC?

I am working with Spring MVC controller project. Below is my Controller and I have a constructor declared which I am specifically using for testing purpose.

@Controller
public class TestController {

    private static KeeperClient testClient = null;

    static {

    // some code here

    }

    /**
     * Added specifically for unit testing purpose.
     * 
     * @param testClient
     */
    public TestController(KeeperClient testClient) {
        TestController.testClient = testClient;
    }

    // some method here

}

Whenever I am starting the server, I am getting below exception -

No default constructor found; nested exception is java.lang.NoSuchMethodException:

But if I remove TestController constructor then it works fine without any problem. What wrong I am doing here?

But if I add this default constructor then it starts working fine -

    public TestController() {

    }