what is the root of classpath for a java web application

I want to display some messages from properties file while user enter some incorrect information and submit the form, but I always got warning message from eclipse console like this:

WARNING: ResourceBundle [messages] not found for MessageSource: Can't find bundle for base name messages, locale en_US
Nov 15, 2017 9:32:42 AM org.springframework.context.support.ResourceBundleMessageSource getResourceBundle    

I config the MessageSource bean in WebConfig.java like this:

public MessageSource messageSource()
    ResourceBundleMessageSource validationSource = new ResourceBundleMessageSource();
    return validationSource;

I put my message.properties like below:

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when I right click on the properties file, it shows its path like this:

enter image description here

so, where is the correct place I should put this properties file? which path is the root of classpath in a java web application?