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The Struts 2 conversion error interceptor is a subclass of the XWork 2 conversion error interceptor.

From the Javadocs of the XWork 2 interceptor:

ConversionErrorInterceptor adds conversion errors from the ActionContext to the Action's field errors.

This interceptor adds any error found in the ActionContext's conversionErrors map as a field error (provided that the action implements ValidationAware). In addition, any field that contains a validation error has its original value saved such that any subsequent requests for that value return the original value rather than the value in the action. This is important because if the value "abc" is submitted and can't be converted to an int, we want to display the original string ("abc") again rather than the int value (likely 0, which would make very little sense to the user).

From the Javadocs of the Struts 2 interceptor:

This interceptor extends ConversionErrorInterceptor but only adds conversion errors from the ActionContext to the field errors of the action if the field value is not null, "", or {""} (a size 1 String array with only an empty String). See ConversionErrorInterceptor for more information, as well as the Type Conversion documentation.


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    Extending the Interceptor

    There are no known extension points for this interceptor.