Difference between Spring MVC formatters and converters

Question

I would need some clarification regarding the difference between Spring MVC formatters and converters.

My understanding of the main difference between them is that the formatter works on data that is going to be displayed to the end user such as a date, SSN or credit card number whereas the converter works on data hidden behind form controls such as the value attribute of an select's option.

Am I right or wrong? Can someone please provide advice and/or samples in order to better explain the difference between the two.

Answer 1

Converters are used to convert one Java type to another Java type. For example, from Long to java.util.Date or from Integer to Color or from String to Date. It can be used in the web tier or any other tier that needs conversion service.

Formatters are used to convert String to another Java type and back. So, one type must be String. You cannot, for example, write a formatter that converts a Long to a Date. Examples of formatters are DateFormatter, for parsing String to java.util.Date and formatting a Date. In addition, formatters' messages can be localized.

Conclusion: formatters are suitable in the web environment, such as a Spring MVC application.