Introducing Fluent Reflection

I am in the processes of releasing the first alpha build of fluent-reflection, you can get the snapshot version from the fluent-reflection snapshot repository.


Reflection code is difficult to write in Java, and even harder to read once it has been written. Although the Java Reflection API allows complete access to the Java runtime type system, the complexity of using the Java Reflection API reduces its usefulness. I don’t want to have to write any more code like this:

final List<Method> getMethods = new ArrayList<Method>();
Class<? super Bean> klass = Bean.class;
while (klass != null) {
   final Method[] declaredMethods = klass.getDeclaredMethods();
   for (final Method method : declaredMethods) {
      if (method.getName().startsWith("get") && 
          method.getParameterTypes().length == 0 && 
          !method.getReturnType().equals(void.class)) {
   klass = klass.getSuperclass();


There are three APIs which have heavily influenced the design of the fluent-reflection API.

  1. LambdaJ
  2. Hamcrest
  3. Jmock 2

All of them are examples of a style of API design known as fluent interfaces. They use a combination of static methods, method chaining, generic methods, static factory methods and object scoping to produce a type safe and readable programming style.

In particular, the combination of method chaining and generic methods can help the user discover the usage of each part of the API and also takes advantage of Java’s static type system to prevent programming errors.

Using fluent-reflection the above code can be re-written in declarative style:

final List<ReflectedMethod> getMethods = 
   object(new Bean()).methods(


The query methods in the API are given queries described by Hamcrest Matchers. So users can easily construct custom and reusable queries.

For example, this Matcher can select methods with a particular annotation:

class MatcherAnnotatedWith extends ReflectionMatcher<ReflectedAnnotated> {
    private final Class<? extends Annotation> annotation;
    public MatcherCallableAnnotatedWith(final Class<? extends Annotation> annotation) {
        this.annotation = annotation;
    @Override protected boolean matchesSafely(final ReflectedAnnotated item) {
        return item.annotation(reflectedTypeReflectingOn(annotation)) != null;
    @Override public void describeTo(final Description description) {
        description.appendText("callable annotated with ").appendValue(annotation);


Because the API uses the de facto standard Hamcrest matchers, and the Java collections framework it can be combined with other libraries in powerful ways.

For example, calling all of the @PostConstruct methods on an Object using LambdaJ and fluent-reflection:


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