Querying methods and properties

In this first recipe about metaprogramming, we begin by looking at the introspection capabilities of Groovy. Introspection is a major feature of the Java language and, by extension, of the Groovy language. Using introspection, we can get the internal information of a class at runtime, including fields, methods, constructors, and so on.

Getting ready

To test out the introspection feature, let's create a couple of Groovy classes:

package org.groovy.cookbook

class Book {

  String title
  Author author
  Long year
  Long pages

  Long getAmazonSalesPosition() {
    new Random().nextInt(1) + 1
  }

  void attachReview(String review) { }

}

class Author {
  String name
  String lastName
}

How to do it...

The following steps offer an example of the introspection capabilities of the language:

1. To check the type of a class, you can just execute the following code snippet:

   assert 'java.lang.String' == String.name
   assert 'org.groovy.cookbook.Author' == Author.name

2. To list...