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 boilerplate code between the web browser and your Java code. This version 4.0.2 works with Jakarta Servlet 4.0.2.
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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
     * @param  ...
     * @param key ...
     * @param data ...
     * @throws ConversionException ...
     */
    @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
     * @return ...
     */
    public String createUniqueId()
    {
        return idGenerator.generate();
    }

    /**
     * The id generator
     * @param idGenerator ...
     */
    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";
}