org.directwebremoting.impl.DefaultCallbackHelper Maven / Gradle / Ivy

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DWR is easy Ajax for Java. It makes it simple to call Java code directly from Javascript. It gets rid of almost all the boiler plate code between the web browser and your Java code.
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/*
 * Copyright 2005 Joe Walker
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.directwebremoting.impl;

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

import org.directwebremoting.ConversionException;
import org.directwebremoting.ScriptSession;
import org.directwebremoting.WebContext;
import org.directwebremoting.WebContextFactory;
import org.directwebremoting.extend.CallbackHelper;
import org.directwebremoting.extend.ConverterManager;
import org.directwebremoting.extend.IdGenerator;
import org.directwebremoting.extend.InboundVariable;
import org.directwebremoting.extend.MethodDeclaration;
import org.directwebremoting.extend.ParameterProperty;
import org.directwebremoting.extend.Property;
import org.directwebremoting.extend.RealRawData;
import org.directwebremoting.ui.Callback;

/**
 * The default implementation of CallbackHelper
 * @author Joe Walker [joe at getahead dot ltd dot uk]
 */
public class DefaultCallbackHelper implements CallbackHelper
{
    /* (non-Javadoc)
     * @see org.directwebremoting.extend.CallbackHelper#saveCallback(org.directwebremoting.proxy.Callback, java.lang.Class)
     */
    @SuppressWarnings("unchecked")
    public  String saveCallback(Callback callback, Class type)
    {
        String key = createUniqueId();

        for (ScriptSession session : callback.getScriptSessions())
        {
            // Save the callback itself
            Map> callbackMap = (Map>) session.getAttribute(KEY_CALLBACK);
            callbackMap.put(key, callback);
            session.setAttribute(KEY_CALLBACK, callbackMap);

            // And save the type of the callback
            Map> typeMap = (Map>) session.getAttribute(KEY_TYPE);
            typeMap.put(key, type);
            session.setAttribute(KEY_TYPE, typeMap);
        }

        return key;
    }

    /**
     * The reverse of {@link CallbackHelper#saveCallback(Callback, Class)}
     * which executes a {@link Callback} which has been called by the browser
     */
    @SuppressWarnings("unchecked")
    public static  void executeCallback(String key, RealRawData data) throws ConversionException
    {
        WebContext webContext = WebContextFactory.get();
        ScriptSession session = webContext.getScriptSession();
        ConverterManager converterManager = webContext.getContainer().getBean(ConverterManager.class);

        Map> typeMap = (Map>) session.getAttribute(KEY_TYPE);
        Class type = typeMap.remove(key);
        session.removeAttribute(KEY_TYPE);
        session.setAttribute(KEY_TYPE, typeMap);

        try
        {
            Method method = Callback.class.getMethod("dataReturned", type);

            Property property = new ParameterProperty(new MethodDeclaration(method), 0);
            InboundVariable iv = data.getInboundVariable();
            Object callbackData  = converterManager.convertInbound(type, iv, property);

            Map> callbackMap = (Map>) session.getAttribute(KEY_TYPE);
            Callback callback = callbackMap.remove(key);
            session.removeAttribute(KEY_TYPE);
            session.setAttribute(KEY_CALLBACK, callbackMap);

            callback.dataReturned((T) callbackData);
        }
        catch (Exception ex)
        {
            throw new ConversionException(type, ex);
        }
    }

    /**
     * Callbacks need a unique ID
     */
    public String createUniqueId()
    {
        return idGenerator.generate();
    }

    /**
     * The id generator
     */
    public void setIdGenerator(IdGenerator idGenerator)
    {
        this.idGenerator = idGenerator;
    }

    /**
     * The id generator
     */
    private IdGenerator idGenerator;

    /**
     * The key that we use in a script session to store Callbacks
     */
    public static final String KEY_CALLBACK = "org.directwebremoting.callback";

    /**
     * The key that we use in a script session to store Callbacks
     */
    public static final String KEY_TYPE = "org.directwebremoting.type";
}