Using @ComponentScan or <context:component-scan /> with only one class

What @Bart said for XML.

If you need to pull in that one class using annotations, add the following to one of your @Configuration classes

@ComponentScan(
    basePackageClasses = YourClass.class, 
    useDefaultFilters = false,
    includeFilters = {
        @ComponentScan.Filter(type = ASSIGNABLE_TYPE, value = YourClass.class)
    })

Simply add is as a bean to your context e.g.

<bean class="my.package.MyClass" />

In addition to the method described by Emerson Farrugia there is a less verbose solution which has been supported since Spring Framework 4.2 as mentioned in the documentation here.

As of Spring Framework 4.2, @Import also supports references regular component classes, analogous to the AnnotationConfigApplicationContext.register method. This is particularly useful if you want to avoid component scanning, by using a few configuration classes as entry points to explicitly define all your components.

So your example would simply become:

@Import(YourClass.class)