BeanUtil.java

/*
 *   This software is distributed under the terms of the FSF 
 *   Gnu Lesser General Public License (see lgpl.txt). 
 *
 *   This program is distributed WITHOUT ANY WARRANTY. See the
 *   GNU General Public License for more details.
 */
package com.scooterframework.common.util;

import java.lang.reflect.Method;
import java.util.StringTokenizer;

import com.scooterframework.common.exception.ExecutionException;
import com.scooterframework.common.exception.MethodCreationException;

/**
 * <tt>BeanUtil</tt> class has helper methods on beans.
 * 
 * @author (Fei) John Chen
 */
public class BeanUtil {

    /**
     * Returns method of an object.
     * 
     * @param clz the class type
     * @param methodName the method name of the object
     * @return the method object
     * @exception MethodCreationException if <tt>bean</tt> or
     *  <tt>method</tt> is null
     */
    public static Method getMethod(Class<?> clz, String methodName) {
        if (clz == null) {
            throw new IllegalArgumentException("BeanUtil.getMethod(): No bean class specified.");
        }
        if (methodName == null) {
            throw new IllegalArgumentException("BeanUtil.getMethod(): No method name specified.");
        }
        
        Method method = null;
		Method[] methods = clz.getMethods();
		for (Method m : methods) {
			if (methodName.equalsIgnoreCase(m.getName())) {
				method = m;
				break;
			}
		}
		
		if (method == null) {
    		throw new MethodCreationException(clz.getName(), methodName);
    	}
        
        return method;
    }
    
    /**
     * Executes a method of a bean instance.
     * 
     * @param instance      the bean instance
     * @param methodName    the method to be executed
     * @param args          input parameters for the method
     * @return return value of the method
     */
    public static Object execute(Object instance, String methodName, Object[] args) {
        if (instance == null) {
            throw new IllegalArgumentException("Input bean instance is null.");
        }
        
        Object result = null;
        try {
            Method m = getMethod(instance.getClass(), methodName);
            result = m.invoke(instance, args);
        }
        catch(Exception ex) {
            throw new ExecutionException(instance.getClass().getName(), methodName, args, ex);
        }
        return result;
    }
    
    /**
     * <p>Gets property of a bean for a <tt>property</tt>. </p>
     * 
     * <pre>
     * Examples:
     *     getBeanProperty(pet, "name") -> pet.getName()
     *     getBeanProperty(pet, "owner.first_name") -> pet.getOwner().getFirstName()
     * </pre>
     * 
     * @param bean        the bean instance
     * @param property    the property name
     * @return value of the property
     */
    public static Object getBeanProperty(Object bean, String property) {
        if (property.indexOf('.') == -1) 
            return _getBeanPropertyData(bean, property);
        
        StringTokenizer st = new StringTokenizer(property, " .");
        Object tmp = bean;
        while(st.hasMoreTokens()) {
            String token = st.nextToken();
            tmp = _getBeanPropertyData(tmp, token);
        }
        
        return tmp;
    }
    
    private static Object _getBeanPropertyData(Object bean, String property) {
        String methodName = "get" + WordUtil.camelize(property);
        return execute(bean, methodName, null);
    }
}