Common utilities library

Published on Maven Central:

implementation group: 'systems.helius', name: 'helius-commons', version: '0.3.0'

Minimum java version: 17

Introspection

To use the introspection ability of this library, simply create an instance of BeanIntrospector. You then call the seek(Class, Object, MethodHandles.Lookup method on it.

Example:

    // Setup
    var structure = new ComplexStructure();

    // Usage
    Set<Foo> found = new BeanIntrospector().seek(Foo.class, structure, MethodHandles.lookup());
    
    // Validation
    assertEquals(2, found.size());
    assertTrue(found.contains(/* Some Foo I know is already hidden in the object graph of the structure */));
    assertTrue(found.contains(/* Another one */));

In this example, IntHolder is a deeply nested (4 classes down) class and attribute within ComplexStructure.

For more examples, look at the tests. You may reuse the same BeanIntrospector across different calls.

The Lookup object

From: Java 17 API A Lookup object can be shared with other trusted code, such as a metaobject protocol. A shared Lookup object delegates the capability to create method handles on private members of the lookup class. Even if privileged code uses the Lookup object, the access checking is confined to the privileges of the original lookup class.

Accessing base Java classes

Add the following JVM options to your launch configuration:

--add-opens java.base/java.lang=ALL-UNNAMED
--add-opens java.base/java.nio=ALL-UNNAMED
--add-opens java.base/sun.nio.ch=ALL-UNNAMED

Read Five Command Line Options To Hack The Java Module System to know more.

Access related exceptions

See: https://stackoverflow.com/a/41265267

Last resort of access in your own classes