The ExtVal framework is very extensible, and extending it is fairly simple. The framework uses the convention over configuration paradigm. This means that if we’re happy with the conventions of the framework, we don’t have to configure anything. As an example of the extensibility of ExtVal, in this section we’re going to change the default behavior of ExtVal’s @Pattern annotation.
The @Pattern annotation accepts an array of Strings for the value argument. This means that more than one regular expression can be used to validate the input. By default, all regular expressions have to be matched in order for an input string to be valid. For example, if the patterns [A-Z].\\S* and [A-Za-z]* are combined, this effectively means that only words starting with a capital letter and containing only the characters a through to z, which may or may not be in capitals, are allowed. Note that this can be achieved with one single expression too—[A-Z].[A-Za-z]*.
Although...