NestedPropertyGetter.java

/**************************************************************************************
 * Copyright (C) 2008 EsperTech, Inc. All rights reserved.                            *
 * http://esper.codehaus.org                                                          *
 * http://www.espertech.com                                                           *
 * ---------------------------------------------------------------------------------- *
 * The software in this package is published under the terms of the GPL license       *
 * a copy of which has been included with this distribution in the license.txt file.  *
 **************************************************************************************/
package com.espertech.esper.event.bean;

import com.espertech.esper.client.EventBean;
import com.espertech.esper.client.EventPropertyGetter;
import com.espertech.esper.client.PropertyAccessException;
import com.espertech.esper.event.EventAdapterService;

import java.util.List;

/**
 * Getter for one or more levels deep nested properties.
 */
public class NestedPropertyGetter extends BaseNativePropertyGetter implements BeanEventPropertyGetter
{
    private final BeanEventPropertyGetter[] getterChain;

    /**
     * Ctor.
     * @param getterChain is the chain of getters to retrieve each nested property
     * @param eventAdapterService is the cache and factory for event bean types and event wrappers
     * @param finalPropertyType type of the entry returned
     * @param finalGenericType generic type parameter of the entry returned, if any
     */
    public NestedPropertyGetter(List<EventPropertyGetter> getterChain, EventAdapterService eventAdapterService, Class finalPropertyType, Class finalGenericType)
    {
        super(eventAdapterService, finalPropertyType, finalGenericType); 
        this.getterChain = new BeanEventPropertyGetter[getterChain.size()];

        for (int i = 0; i < getterChain.size(); i++)
        {
            this.getterChain[i] = (BeanEventPropertyGetter) getterChain.get(i);
        }
    }

    public Object getBeanProp(Object value) throws PropertyAccessException {
        if (value == null)
        {
            return value;
        }

        for (int i = 0; i < getterChain.length; i++)
        {
            value = getterChain[i].getBeanProp(value);

            if (value == null)
            {
                return null;
            }
        }
        return value;
    }

    public boolean isBeanExistsProperty(Object value) {
        if (value == null)
        {
            return false;
        }

        int lastElementIndex = getterChain.length - 1;

        // walk the getter chain up to the previous-to-last element, returning its object value.
        // any null values in between mean the property does not exists
        for (int i = 0; i < getterChain.length - 1; i++)
        {
            value = getterChain[i].getBeanProp(value);

            if (value == null)
            {
                return false;
            }
        }

        return getterChain[lastElementIndex].isBeanExistsProperty(value);
    }

    public Object get(EventBean eventBean) throws PropertyAccessException
    {
        return getBeanProp(eventBean.getUnderlying());
    }

    public boolean isExistsProperty(EventBean eventBean)
    {
        return isBeanExistsProperty(eventBean.getUnderlying());
    }
}