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An application to get controlled access to private members of Java classes

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package com.almondtools.xrayinterface;

import static com.almondtools.xrayinterface.Converter.convertArguments;
import static com.almondtools.xrayinterface.Converter.convertResult;

import java.lang.invoke.MethodHandle;
import java.lang.reflect.InvocationTargetException;

/**
 * Invokes a given method.
 */
public class MethodInvoker implements MethodInvocationHandler {

	private String name;
	private MethodHandle method;
	private Class[] targetParameterTypes;
	private Class targetReturnType;

	/**
	 * Invokes the given method
	 * @param name the name of the method
	 * @param method the method to invoke
	 */
	public MethodInvoker(String name, MethodHandle method) {
		this.name = name;
		this.method = method;
	}

	/**
	 * Invokes a given method. Beyond {@link #MethodInvoker(String,MethodHandle)} this constructor also converts the method signature
	 * @param name the name of the method
	 * @param method the method to invoke
	 * @param targetReturnType the return type the result of the actual invocation should be converted to
	 * @param targetParameterTypes the types the parameters should be converted from
	 * @see Convert
	 */
	public MethodInvoker(String name, MethodHandle method, Class targetReturnType, Class[] targetParameterTypes) {
		this(name, method);
		this.targetReturnType = targetReturnType;
		this.targetParameterTypes = targetParameterTypes;
	}

	public String getName() {
		return name;
	}

	public Class getResultType() {
		return method.type().returnType();
	}

	public Class[] getTargetParameterTypes() {
		return targetParameterTypes;
	}

	public Class getTargetReturnType() {
		return targetReturnType;
	}

	@Override
	public Object invoke(Object object, Object... args) throws Throwable {
		MethodHandle unimorphMethod = method.bindTo(object);
		return r(unimorphMethod.invokeWithArguments(a(args)));
	}

	private Object[] a(Object[] args) throws InstantiationException, IllegalAccessException, NoSuchMethodException, InvocationTargetException {
		if (targetParameterTypes == null || targetParameterTypes.length == 0) {
			return args;
		}
		return convertArguments(targetParameterTypes, method.type().dropParameterTypes(0, 1).parameterArray(), args);
	}

	private Object r(Object result) throws NoSuchMethodException {
		if (targetReturnType == null) {
			return result;
		}
		return convertResult(targetReturnType, method.type().returnType(), result);
	}

}