Is InputPreprocessor interface doing too much?

[drapostolos]

The contract for the InputPreprocessor interface currently states :

 If a null object is returned from this method, the called {@link Parser} implementation is
expected to return either:     
 * An empty {@link Collection}/ {@link Map} / Array type.
 * A null object for types other than above.

It should not be up to the InputPreprocessor to decide if an input string is considered a null object or not.

How about change the contract of InputPreprocessor interface to simply receive a string and return a string (in other words just pre-process the string as the name sugests). It should not be allowed to return a null object.

A second callback interface would be needed instead to decide if a input string should represent a null object or not, something like this:

public interface NullStringStrategy {
    boolean isNullString(String input);
}

Your comments?

[drapostolos]

This has been pushed to master branch now.

    public interface NullStringStrategy {
        boolean isNullString(String input, NullStringStrategyHelper helper);
    }

Where the contract of InputPreprocessor interface has changed to the following:

    /**
     * Callback interface that allows clients to do their own preparation of the input string to parse.
     * Implementations of this interface are expected to be immutable.
     * 
     * @see <a href="https://github.com/drapostolos/type-parser/wiki/User-Guide"
     *      target="_blank">User-Guide</a>
     */
    public interface InputPreprocessor {

        /**
         * Prepares the input string to be parsed. Must return a {@link String} object.
         * <p/>
         * Returning a <code>null</code> object is not supported. If a null object is return, an
         * {@link UnsupportedOperationException} will be thrown.
         * 
         * @param input String to prepare for parsing. This may be a {@code NullString} but will never
         *        be {@code null}.
         * @param helper Helper class injected automatically by the {@link TypeParser}.
         * @return a prepared string to be parsed.
         * @throws RuntimeException Any exception thrown within this method will be wrapped and
         *         re-thrown as a {@link TypeParserException} to the client.
         */
        String prepare(String input, InputPreprocessorHelper helper);
    }

[drapostolos]

Released in v0.4.0