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Type conversion

Type conversion is a mechanism for converting data from one type to another. For example, convert the string “1234” to an integer. The conversion is very useful when moving from one layer to another in DDD-based architectures. It is also used in the web feature to convert path param to typed values in the controller.


Using conversion

The conversion is used via the Conversion service which is accessible via direct injection.

public final class ExampleConversionService {

    private final Conversion conversion;

    @Inject
    public ExampleConversionService(final Conversion conversion) {
        this.conversion = conversion;
    }

    public void example() {
        final String boolAsString = "true";
        final Boolean bool = conversion.convert(boolAsString, Boolean.class);
        // or conversion.convert(boolAsString, String.class, Boolean.class);
    }
}

Creating a new converter

The creation of a new converter is very simple, you just have to implement the TypeConverter interface and to register this implementation with the ConverterManager. The registration will be done automatically if the newly created converter is in a package which will be scanned at the start of the application (see the voidframework.core.acceptedScanPaths parameter).

/**
 * Convert a {@code String} into an {@code Boolean}.
 */
public final class StringToBooleanConverter implements TypeConverter<String, Boolean> {

    private static final List<String> VALUE_TRUE_LIST = Arrays.asList("1", "true", "y", "yes");

    @Override
    public Boolean convert(final String source) {
        // The "source" variable will never be null
        return VALUE_TRUE_LIST.contains(source.toLowerCase(Locale.ENGLISH));
    }
}