es.deusto.weblab.client.comm.WebLabRequestCallback.java Source code

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Here is the source code for es.deusto.weblab.client.comm.WebLabRequestCallback.java

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/*
* Copyright (C) 2005 onwards University of Deusto
* All rights reserved.
*
* This software is licensed as described in the file COPYING, which
* you should have received as part of this distribution.
*
* This software consists of contributions made by many individuals, 
* listed below:
*
* Author: Pablo Ordua <pablo@ordunya.com>
*
*/
package es.deusto.weblab.client.comm;

import com.google.gwt.http.client.Request;
import com.google.gwt.http.client.RequestCallback;
import com.google.gwt.http.client.Response;

import es.deusto.weblab.client.comm.callbacks.IWebLabAsyncCallback;
import es.deusto.weblab.client.comm.exceptions.CommunicationException;
import es.deusto.weblab.client.comm.exceptions.ServerException;

/**
 * Callback to be invoked whenever a request finishes. Holds an internal
 * IWlAsyncCallback, which will be invoked if an error occurs. 
 * 
 * Though this callback does apparently have methods to support both success and error 
 * notification, receiving a response successfully does not necessarily mean that the
 * request succeeded. Hence the need for the aforementioned callback within this
 * callback.
 * 
 * Most often, a callback extending this WlRequestCallback will be used as the one 
 * to receive and parse the raw result of a query (that is, for instance, the JSON-encoded 
 * result). These extending classes will also rather often accept some kind of 
 * IWlAsyncCallback, which will be the one to handle the higher level (already parsed, 
 * not raw) result and logic. This extended IWlAsyncCallback will often include an 
 * onSuccess method, with a signature specific to that higher level response.
 */
abstract public class WebLabRequestCallback implements RequestCallback {

    private final IWebLabAsyncCallback callback;

    /**
     * Constructs the WlRequestCallback.
     * @param callback IWlAsyncCallback to be invoked by the WlRequestCallback if
     * an error occurs. For instance, if the server returns an error code, or if the
     * request fails.
     */
    public WebLabRequestCallback(IWebLabAsyncCallback callback) {
        this.callback = callback;
    }

    @Override
    public void onError(Request request, Throwable exception) {
        this.callback.onFailure(new CommunicationException(exception.getMessage(), exception));
    }

    @Override
    public void onResponseReceived(Request request, Response response) {
        final int stateCode = response.getStatusCode();
        // 5XX and 4XX are server errors
        // 500 might be returned when a SOAP-Fault is raised, so we're not going to filter it
        final int firstNumber = (stateCode / 100) % 1000;
        if (firstNumber == 4 || (firstNumber == 5 && stateCode != 500)) {
            this.callback.onFailure(
                    new ServerException("Couldn't contact with the server: " + response.getStatusText()));
        } else {
            this.onSuccessResponseReceived(response.getText());
        }
    }

    public abstract void onSuccessResponseReceived(String message);
}