Hier

Hier is a library supports JVM class hierarchy lookup by extending JNI interface.

Installation

To use this Hier, you'll need to have complete installation of JDK on machine (additionally, environment variables should be set, e.g. JAVA_HOME).

Usage

To use without calling from an exist Java application, you'll need to enable invocation feature, then use ClassPool::from_permanent_env to construct a ClassPool.

Get common super class of 2 classes

use hier::class::Class;
use hier::classpool::ClassPool;
use hier::errors::HierError;

fn main() {
    let mut cp = ClassPool::from_permanent_env().unwrap();
    let mut integer_class = cp.lookup_class("java.lang.Integer").unwrap();
    let mut float_class = cp.lookup_class("java.lang.Float").unwrap();
    let mut most_common_superclass =
        find_most_common_superclass(&mut cp, &mut integer_class, &mut float_class).unwrap();

    println!("{}", most_common_superclass.name(&mut cp).unwrap());
}

fn find_most_common_superclass(
    cp: &mut ClassPool,
    class1: &mut Class,
    class2: &mut Class,
) -> Result<Class, HierError> {
    if class2.is_assignable_from(cp, class1)? {
        return Ok(class1.clone());
    }

    if class1.is_assignable_from(cp, class2)? {
        return Ok(class2.clone());
    }

    if class1.is_interface(cp)? || class2.is_interface(cp)? {
        return cp.lookup_class("java.lang.Object");
    }

    let mut cls1 = class1.clone();
    while {
        cls1 = match cls1.superclass(cp)? {
            Some(superclass) => superclass,
            None => return Ok(cls1),
        };

        !cls1.is_assignable_from(cp, class2)?
    } {}

    Ok(cls1)
}

Get derived interface of class

use hier::classpool::ClassPool;

fn main() {
    let mut cp = ClassPool::from_permanent_env().unwrap();
    let mut integer_class = cp.lookup_class("java.lang.Integer").unwrap();
    let mut interfaces = integer_class.interfaces(&mut cp).unwrap();
    let interface_names = interfaces
        .iter_mut()
        .map(|interface_class| interface_class.name(&mut cp))
        .collect::<Result<Vec<_>, _>>()
        .unwrap();

    println!("{interface_names:#?}");
}

License

Hier is licensed under MIT License.