Reflection support is currently reengineered. This chapter might be outdated and will be rewritten when work is complete.
Bytecoder is an AOT (Ahead-of-time) compiler. As this, it has to determine the set
of classes at compile time. It does this by running a statical dependency analysis which
starts at a class implementing a public static void main(String[] args) method and
builds a dependency tree from there resulting in the final set of classes and methods
that must be included to make the program valid.
However, things start to get tricky once we use the Java Reflection API.
The most famous part of the Reflection API is the Class.forName method and its derivatives.
Here, the class to be resolved is defined as runtime. This is a problem for an AOT compiler.
Bytecoder tries so solve this problem using a set of heuristics and configuration.
Classes that are very likely to be resolved by reflection are automatically included by the compiler.
Some prominent examples are implementations of java.nio.charset.Charset or java.lang.CharacterData.
There is also a compiler option available by the CLI or Maven Plugin to add additional classes.
Only zero-arg constructors are supported yet.
The following APIs are supported by Bytecoder by all backends:
Class runtimeClass = Class.forName("FullQualifiedClassNameHere");
Object instance = runtimeClass.newInstance(); // Method 1 to instantiate a class
cl.getConstructor(new Class[0]).newInstance(); // Method 2 to instantiate a class
The JavaScript and Wasm backends provide support for reflective field access:
Field fields[] = ReflectionTarget.class.getDeclaredFields();
Field f = BaseClass.class.getField("staticField"); // Get field by name
f.getName(); // Retrieve field name
f.getModifiers(); // Retrieve modifiers
f.get(BaseClass.class); // Get static or instance value
f.put(BaseClass.class, "newvalue"); // Put static or instance value
Class.isPrimitive() // Check if the class represents a primitive value
Classes available to the reflection API can be configured by placing a bytecoder-reflection.json file into the
root of the classpath. The syntax of the configuration file is shown in the follwing example:
{
"sun.nio.cs.UTF_8": { // The full-qualified class name is used as a key here
// Please note that you have to include subclasses
// and innerclasses of this class explicitly
"enableClassForName": true // The class is available by Class.forName()
// This also includes reflective read and write
// field access for all declared fields
},
}
The ServiceLocator API is currently not supported!