spring mvc annotation validation integer

You can add the following to your file which controls your error messages (these are the generic ones it looks for in the case of a type mismatch:

typeMismatch.commandObjectName.aNumber=You have entered an invalid number for ...
typeMismatch.aNumber=You have entered an invalid number for ...
typeMismatch.java.lang.Integer=You have input a non-numeric value into a field expecting a number...
typeMismatch=You have entered incorrect data on this page.  Please fix (Catches all not found)

For those who did not get the idea right here is what to do in spring 4.2.0. Create a file name messages.properties in WEB-INF > classes folder. And put the above type mismatch messages in that file. In spring configuration or servlet.xml file create the following bean.

<beans:bean id="messageSource" class="org.springframework.context.support.ResourceBundleMessageSource">
<beans:property name="basename" value="messages"></beans:property>
</beans:bean>

And for your model attribute like private Integer aNumber; in the question along with other validation rules this rule is also applied for type mismatch conversion. You will get your desired message in this.

<form:errors path="aNumber"></form:errors>

Hope it helps others.