reflection

A lightweight and easy to use runtime reflection library.

reflection is a lightweight and easy to use library allowing you to scan the content of a ClassLoader's classpath at runtime.

// Print all the resources of the specified classLoader to stdout
Reflection
	.of(ClassPathScanner.of(classLoader))
	.getResources()
	.forEach(System.out::println);

Usage

A single entry point is exposed to use the reflection library: the Reflection class, which requires a Scanner instance to provide resources metadata.

Use the ClassPathScanner.of(instance) method to create a new scanner object that will perform the reflection process. You can call the filter method to add a custom Filter (see the Filters section below) applied during the classpath scanning.

When you're all set, you just have to call the Reflection.of(scanner) method. It will run the reflection process and return a fully initialized Reflection object.

final Scanner scanner = ClassPathScanner
	.of(classLoader)
	.filter(PackageFilter.withSubpackages("com.example"))
	.filter(AnnotationFilter.all(MyAnnotation.class));

final Reflection reflection = Reflection.of(scanner);

You can obviously create your own implementation of the Scanner interface, and use it as the configuration object for a Reflection instance.

The Reflection object exposes a set of simple methods:

• getResources() return all the scanned resources metadata.

• getSimpleResources() return all the non-class resources (.properties, .xml, ...) metadata.

• getClasses() return all the classes metadata.

• getClasses(packageName) return all classes metadata of resources located in a specific package.

• getClassesRecursively(packagePrefix) return all classes metadata by recursively searching into subpackages of packagePrefix.

• getTopLevelClasses() return only the top level classes (inner classes are ignored) metadata.

• getTopLevelClasses(String packageName) return only the top level classes metadata of resources located in a specific package.

• getTopLevelClassesRecursively(String packagePrefix) return all the top level classes metadata by recursively searching into subpackages of packagePrefix.

• getTypes() load and return all the scanned classes.

• getTypes(packageName) load and return all the classes located in a specific package.

• getTypesRecursively(packagePrefix) load and return all the classes by recursively searching into subpackages of packagePrefix.

• getAnnotatedTypes(annotation) load and return all the classes annotated with the specified annotation.

• getAnnotatedTypes(annotation, packageName) load and return all the classes annotated with the specified annotation and located in a specific package.

• getAnnotatedTypesRecursively(annotation, packagePrefix) load and return all the classes annotated with the specified annotation by recursively searching into subpackages of packagePrefix.

Filters

In order to refine the reflection process, you can add custom Filter objects while building your ClassPathScanner instance.

Filters are simple classes implementing the Filter functional interface and its accept(classLoader, resourceName) method:

// This is a silly example. Please don't do this.
public class AngryFilter implements Filter {
	
	@Override
	public boolean accept(final ClassLoader classLoader, final String resourceName) {
		return false;
	}
}

Your filter can then be used during the ClassPathScanner configuration phase:

ClassPathScanner
	.of(classLoader)
	.filter(AngryFilter::new);

Simple filters can also be implemented using a lambda:

ClassPathScanner
	.of(classLoader)
	.filter((resourceClassLoader, resourceName) -> resourceName.contains("Filter"));

3 default filters are shipped with the reflection library:

• ManifestFilter which excludes the META-INF/MANIFEST.MF file.
• PackageFilter which allows you to filter the resource's package during the reflection process.
• AnnotationFilter which will only accept the classes annotated with a specific set of annotations.

Installation

Gradle:

allprojects {
	repositories {
		...
		maven { url 'https://jitpack.io' }
	}
}

dependencies {
	implementation 'com.github.MrKloan:reflection:1.0.1'
}

Maven:

<repositories>
	<repository>
		<id>jitpack.io</id>
		<url>https://jitpack.io</url>
	</repository>
</repositories>

<dependencies>
	<dependency>
		<groupId>com.github.MrKloan</groupId>
		<artifactId>reflection</artifactId>
		<version>1.0.1</version>
	</dependency>
</dependencies>