Smith.java

/*
 *  Copyright (C) 2014 The AppCan Open Source Project.
 *
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU Lesser General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.

 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU Lesser General Public License for more details.

 *  You should have received a copy of the GNU Lesser General Public License
 *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 */

package org.zywx.wbpalmstar.widgetone;

import java.lang.reflect.Field;

public class Smith<T> {
    private Object obj;
    private String fieldName;

    private boolean inited;
    private Field field;

    public Smith(Object obj, String fieldName) {
        if (obj == null) {
            throw new IllegalArgumentException("obj cannot be null");
        }
        this.obj = obj;
        this.fieldName = fieldName;
    }

    private void prepare() {
        if (inited)
            return;
        inited = true;

        Class<?> c = obj.getClass();
        while (c != null) {
            try {
                Field f = c.getDeclaredField(fieldName);
                f.setAccessible(true);
                field = f;
                return;
            } catch (Exception e) {
            } finally {
                c = c.getSuperclass();
            }
        }
    }

    public T get() throws NoSuchFieldException, IllegalAccessException,
            IllegalArgumentException {
        prepare();

        if (field == null)
            throw new NoSuchFieldException();

        try {
            @SuppressWarnings("unchecked")
            T r = (T) field.get(obj);
            return r;
        } catch (ClassCastException e) {
            throw new IllegalArgumentException("unable to cast object");
        }
    }

    public void set(T val) throws NoSuchFieldException, IllegalAccessException,
            IllegalArgumentException {
        prepare();

        if (field == null)
            throw new NoSuchFieldException();

        field.set(obj, val);
    }
}