We've released Cucumber-JVM v4.2.0! There have been several smaller releases since the announcement of v4.0.0, but this one is worth some extra attention. As always, the full changelog can be found in the repository.

Anonymous Parameter Types

In Cucumber-JVM 2.x, it was possible to capture any string and have it converted to a type instance. With the release of Cucumber Expressions in Cucumber 3.0, we removed XStream, which also removed the ability to keep that behavior. We're happy to announce that this behavior is back! By installing an object mapper (Jackson in this example) the following step definitions are usable:

Given("^there is some date (.*)$", (Date a) -> { })

Given("^there is some transaction (.*) (.*)$", (BigDecimal a, Currency b) -> { })

Given("^there is some type (.*)$", (TypeEnum a) -> { })

Likewise for their Cucumber Expression equivalent:

Given("there is some date {}", (Date a) -> { })

Given("there is some transaction {} {}", (BigDecimal a, Currency b) -> { })

Given("there is some type {}", (TypeEnum a) -> { })

For Cucumber-JVM the object mapper can be installed by placing an
implementation of TypeRegistryConfigurer on the glue path.

public class ParameterTypes implements TypeRegistryConfigurer {

    public Locale locale() {
        return ENGLISH;

    public void configureTypeRegistry(TypeRegistry typeRegistry) {
        Transformer transformer = new Transformer();

    private class Transformer implements ParameterByTypeTransformer, TableEntryByTypeTransformer, TableCellByTypeTransformer {
        ObjectMapper objectMapper = new ObjectMapper();

        public Object transform(String s, Type type) {
            return objectMapper.convertValue(s, objectMapper.constructType(type));

        public <T> T transform(Map<String, String> map, Class<T> aClass, TableCellByTypeTransformer tableCellByTypeTransformer) {
            return objectMapper.convertValue(map, aClass);

        public <T> T transform(String s, Class<T> aClass) {
            return objectMapper.convertValue(s, aClass);

Implicit Anonymous Parameter Types

Formally the anonymous parameter type is defined as:

  name: ""
  regexps: [\.*\]
  transformer: s -> s
  useForSnippets: false
  preferForRegexMatch: true

When matching a step to a Cucumber expression, Cucumber inspects the parameter types of the step definition method and replaces the identity transform s -> s with s -> transform(s, type).

Additionally, when using a regular expression with a capture group that does not have a predefined parameter type, a new anonymous parameter type will be created for that capture group. As such the following step definitions are also usable:

Given("^there is some date ([0-9]{4}-[0-9]{2}-[0-9]{2})$", (Date a) -> { })

Given("^there is some transaction ([0-9]+) ([A-Z]{3})$", (BigDecimal a, Currency b) -> { })

Given("^there is some type (RED|GREEN|YELLOW)$", (TypeEnum a) -> { })

Built in Object Mapper

While recommended, it is not required to install an object mapper.

Cucumber comes with a built-in object mapper that can handle most basic types. Aside from Enum it supports conversion to String, BigInteger, BigDecimal, Byte, Short, Integer, Long, Float, Double and String.

Full changelog