com.almondtools.picklock.FieldSetter Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of picklock Show documentation

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

There is a newer version: 0.2.7

package com.almondtools.picklock;

import static com.almondtools.picklock.Converter.convertArgument;

import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Modifier;

/**
 * Wraps a field with modification (setter) access.
 */
public class FieldSetter implements MethodInvocationHandler {

	private Field field;
	private Class target;

	/**
	 * Sets a value on the given field.
	 * @param field the field to access
	 */
	public FieldSetter(Field field) {
		this.field = field;
		field.setAccessible(true);
		if (isFinal(field)) { 
			makeNonFinal(field);
		}
	}
	
	/**
	 * Sets a value on the given field. Beyond {@link #FieldSetter(Field)} this constructor also converts the argument
	 * @param field the field to access
	 * @param target the target signature (source arguments)
	 * @see Convert 
	 */
	public FieldSetter(Field field, Class target) {
		this(field);
		this.target = target;
	}

	private boolean isFinal(Field field) {
		return (field.getModifiers() & Modifier.FINAL) == Modifier.FINAL;
	}

	private void makeNonFinal(Field field) {
		try {
			Field modifiersField = Field.class.getDeclaredField("modifiers");
			modifiersField.setAccessible(true);
			modifiersField.setInt(field, field.getModifiers() & ~Modifier.FINAL);
		} catch (Exception e) {
			// omit this exception
		}
	}

	@Override
	public Object invoke(Object object, Object... args) throws Throwable {
		if (args == null || args.length != 1) {
			throw new IllegalArgumentException("setters can only be invoked with exactly one argument, was " + (args == null ? "null" : String.valueOf(args.length)) + " arguments");
		}
		Object arg = a(args[0]);
		if (arg != null && !BoxingUtil.getBoxed(field.getType()).isInstance(arg)) {
			throw new ClassCastException("defined type of " + field.getName() + " is " + arg.getClass().getSimpleName() + ", but assigned type was " + field.getType().getSimpleName());
		}
		field.set(object, arg);
		return null;
	}

	private Object a(Object arg) throws InstantiationException, IllegalAccessException, NoSuchMethodException, InvocationTargetException {
		if (target == null) {
			return arg;
		}
		return convertArgument(target, field.getType(), arg);
	}

}