ProxyBase.java

/* Copyright (c) 2001 - 2008 TOPP - www.openplans.org. All rights reserved.
 * This code is licensed under the GPL 2.0 license, available at the root
 * application directory.
 */
package org.geoserver.catalog.impl;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.util.HashMap;

/**
 * Base class for catalog proxies.
 * <p>
 * This class maintains a map of "dirty" properties which have been
 * set via a well formed java bean setter method. Subsequence getter 
 * methods accessing   
 * </p>
 * @author Justin Deoliveira, The Open Planning Project
 *
 */
public class ProxyBase implements InvocationHandler {

    /** 
     * "dirty" properties 
     */
    private HashMap<String,Object> properties;
    
    public Object invoke(Object proxy, Method method, Object[] args)
        throws Throwable {
    
        //getter?
        if ( ( method.getName().startsWith( "get")  || method.getName().startsWith( "is" ) ) 
                && method.getParameterTypes().length == 0 ) {
            
            String property = method.getName().substring( 
                    method.getName().startsWith( "get") ? 3 : 2 );
            
            return handleGet( proxy, method, property );
        }
        //setter?
        if ( method.getName().startsWith( "set") && args.length == 1) {
            
            String property = method.getName().substring( 3 );
            
            handleSet( proxy, method, args[0], property );
            return null;
        }

        //some other
        return handleOther( proxy, method, args );
    }

    protected Object handleGet( Object proxy, Method method, String property ) throws Throwable {
        //intercept getter to check the dirty property set
        if ( properties != null && properties().containsKey( property ) ) {
            //return the previously set object
            return properties().get( property );
        }
        else {
            return handleGetUnSet( proxy, method, property );
        }
    }
    
    protected Object handleGetUnSet( Object proxy, Method method, String property ) throws Throwable {
        return method.invoke( proxy, null );
    }
    
    protected void handleSet( Object proxy, Method method, Object value, String property ) throws Throwable {
        properties().put( property, value );   
    }
    
    protected Object handleOther( Object proxy, Method method, Object[] args ) throws Throwable {
        return method.invoke( proxy, args );
    }
    
    protected HashMap<String,Object> properties() {
        if ( properties != null ) {
            return properties;
        }
        
        synchronized (this) {
            if ( properties != null ) {
                return properties;
            }
            
            properties = new HashMap<String,Object>();
        }
        
        return properties;
    }

}