Java tutorial
/* * Copyright 2009 Google Inc. * * 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 com.google.gwt.jsonp.client; import com.google.gwt.core.client.JavaScriptObject; import com.google.gwt.user.client.rpc.AsyncCallback; /** * Class to send cross domain requests to an http server. The server will receive a request * including a callback url parameter, which should be used to return the response as following: * * <pre><callback>(<json>);</pre> * * where <callback> is the url parameter (see {@link #setCallbackParam(String)}), and * <json> is the response to the request in json format. * * This will result on the client to call the corresponding {@link AsyncCallback#onSuccess(Object)} * method. * * <p> * If needed, errors can be handled by a separate callback: * * <pre><failureCallback>(<error>);</pre> * * where <error> is a string containing an error message. This will result on the client to * call the corresponding {@link AsyncCallback#onFailure(Throwable)} method. See * {@link #setFailureCallbackParam(String)}. * * <p> * Example using <a href="http://code.google.com/apis/gdata/json.html#Request">JSON Google Calendar * GData API</a>: * * <pre> * String url = "http://www.google.com/calendar/feeds/developer-calendar@google.com/public/full" + * "?alt=json-in-script"; * JsonpRequestBuilder jsonp = new JsonpRequestBuilder(); * jsonp.requestObject(url, * new AsyncCallback<Feed>() { * public void onFailure(Throwable throwable) { * Log.severe("Error: " + throwable); * } * * public void onSuccess(Feed feed) { * JsArray<Entry> entries = feed.getEntries(); * for (int i = 0; i < entries.length(); i++) { * Entry entry = entries.get(i); * Log.info(entry.getTitle() + * " (" + entry.getWhere() + "): " + * entry.getStartTime() + " -> " + * entry.getEndTime()); * } * } * }); * </pre> * * This example uses these overlay types: * * <pre> * class Entry extends JavaScriptObject { * protected Entry() {} * * public final native String getTitle() /*-{ * return this.title.$t; * }-*/; * * public final native String getWhere() /*-{ * return this.gd$where[0].valueString; * }-*/; * * public final native String getStartTime() /*-{ * return this.gd$when ? this.gd$when[0].startTime : null; * }-*/; * * public final native String getEndTime() /*-{ * return this.gd$when ? this.gd$when[0].endTime : null; * }-*/; * } * * class Feed extends JavaScriptObject { * protected Feed() {} * * public final native JsArray<Entry> getEntries() /*-{ * return this.feed.entry; * }-*/; * } * </pre> * * </p> */ public class JsonpRequestBuilder { private int timeout = 10000; private String callbackParam = "callback"; private String failureCallbackParam = null; private String predeterminedId = null; /** * Returns the name of the callback url parameter to send to the server. The * default value is "callback". */ public String getCallbackParam() { return callbackParam; } /** * Returns the name of the failure callback url parameter to send to the * server. The default is null. */ public String getFailureCallbackParam() { return failureCallbackParam; } /** * Returns the expected timeout (ms) for this request. */ public int getTimeout() { return timeout; } public JsonpRequest<Boolean> requestBoolean(String url, AsyncCallback<Boolean> callback) { return send(url, callback, false); } public JsonpRequest<Double> requestDouble(String url, AsyncCallback<Double> callback) { return send(url, callback, false); } public JsonpRequest<Integer> requestInteger(String url, AsyncCallback<Integer> callback) { return send(url, callback, true); } /** * Sends a JSONP request and expects a JavaScript object as a result. The caller can either use * {@link com.google.gwt.json.client.JSONObject} to parse it, or use a JavaScript overlay class. */ public <T extends JavaScriptObject> JsonpRequest<T> requestObject(String url, AsyncCallback<T> callback) { return send(url, callback, false); } public JsonpRequest<String> requestString(String url, AsyncCallback<String> callback) { return send(url, callback, false); } /** * Sends a JSONP request and does not expect any results. */ public void send(String url) { send(url, null, false); } /** * Sends a JSONP request, does not expect any result, but still allows to be notified when the * request has been executed on the server. */ public JsonpRequest<Void> send(String url, AsyncCallback<Void> callback) { return send(url, callback, false); } /** * @param callbackParam The name of the callback url parameter to send to the server. The default * value is "callback". */ public void setCallbackParam(String callbackParam) { this.callbackParam = callbackParam; } /** * @param failureCallbackParam The name of the failure callback url parameter to send to the * server. The default is null. */ public void setFailureCallbackParam(String failureCallbackParam) { this.failureCallbackParam = failureCallbackParam; } public void setPredeterminedId(String id) { this.predeterminedId = id; } /** * @param timeout The expected timeout (ms) for this request. The default is 10s. */ public void setTimeout(int timeout) { this.timeout = timeout; } private <T> JsonpRequest<T> send(String url, AsyncCallback<T> callback, boolean expectInteger) { JsonpRequest<T> request; if (predeterminedId != null) { request = new JsonpRequest<T>(callback, timeout, expectInteger, callbackParam, failureCallbackParam, predeterminedId); } else { request = new JsonpRequest<T>(callback, timeout, expectInteger, callbackParam, failureCallbackParam); } request.send(url); return request; } }