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Reflection

Utility methods for reflection.

The classes in this library offer utility methods for certain common (simple) reflection tasks. For more sophisticated tasks like classpath scanning or metadata extraction, the reflections library may be used.

Maven coordinates

<dependency>
  <groupId>de.javagl</groupId>
  <artifactId>reflection</artifactId>
  <version>0.0.4</version>
</dependency>

The main classes in this library are named according to the entities that they operate on:

These classes offer utility methods that are usually just wrappers around the methods of the corresponding JDK classes (Class, Field, Constructor and Method, respectively).

Unchecked and Optional

The methods in these classes generally come in two flavors:

  • An ...Unchecked version that wraps all checked exceptions and security exceptions from the underlying call into an unchecked ReflectionException
  • An ...Optional version that tries to silently ignore any errors and returns null, an empty list, or does nothing at all. (Make sure to use this only when you know what you're doing...)

Filtering with the Members class

The Members class contains methods that may be used via method references as predicates for filtering streams. Additionally, the Fields and Methods class offer convenience methods that allow passing in multiple predicates at once. For example, to obtain all public and static methods of a class whose names start with get, the following code may be used:

List<Method> publicStaticGetters = 
    Methods.getAllOptional(Example.class,
        Members::isPublic, 
        Members::isStatic,
        m -> m.getName().startsWith("get"));

Parsing constructors and methods

The Methods and the Constructors class offer utility methods for parsing strings that have been created from the Method or Constructor object, respectively.

For example, there may be a class with the following method:

public class ExampleClass
{
    public <T> void exampleMethod(
        List<? extends T> list, 
        Collection<? super T> collection) 
    { ... }
}

The method in this class has two different string representations:

  • Created with Method#toString : "public void com.example.ExampleClass.exampleMethod(java.util.List,java.util.Collection)"
  • Created with Method#toGenericString : "public <T> com.example.ExampleClass.exampleMethod(java.util.List<? extends T>,java.util.Collection<? super T>)"

The Methods#parseMethodUnchecked method may be used to parse the Method object from these string representations:

String string = ...; // See above
String genericString = ...; // See above

Method methodFromString = Methods.parseMethodUnchecked(string);
Method methodFromGenericString = Methods.parseMethodUnchecked(genericString);

The same applies, analogously, for Constructor objects and the Constructors#parseConstructorUnchecked method.

Versions:

  • 0.0.5-SNAPSHOT

    ...

  • 0.0.4 (2019-03-22)

    Added option to accept type parameters in generic method strings

  • 0.0.2 (2019-03-22)

    Bugfix in method parser

  • 0.0.1 (2018-11-28)

    Initial release