package autotest.common;
import com.google.gwt.core.client.GWT;
import com.google.gwt.core.client.JavaScriptObject;
import com.google.gwt.core.client.GWT.UncaughtExceptionHandler;
import com.google.gwt.dom.client.Element;
import com.google.gwt.json.client.JSONObject;
import com.google.gwt.user.client.Timer;
import java.util.HashMap;
import java.util.Map;
/**
* JsonRpcProxy that uses "JSON with Padding" (JSONP) to make requests. This allows it to get
* around the Same-Origin Policy that limits XmlHttpRequest-based techniques. However, it requires
* close coupling with the server and it allows the server to execute arbitrary JavaScript within
* the page, so it should only be used with trusted servers.
*
* See http://code.google.com/docreader/#p=google-web-toolkit-doc-1-5&s=google-web-toolkit-doc-1-5&t=Article_UsingGWTForJSONMashups.
* Much of the code here is borrowed from or inspired by that article.
*/
public class PaddedJsonRpcProxy extends JsonRpcProxy {
private static final int REQUEST_TIMEOUT_MILLIS = 60000;
private static final String SCRIPT_TAG_PREFIX = "__jsonp_rpc_script";
private static final String CALLBACK_PREFIX = "__jsonp_rpc_callback";
private static int idCounter = 0;
private String rpcUrl;
private static class JsonpRequest {
private int requestId;
private String requestData;
private Element scriptTag;
private String callbackName;
private Timer timeoutTimer;
private JsonRpcCallback rpcCallback;
private boolean timedOut = false;
public JsonpRequest(String requestData, JsonRpcCallback rpcCallback) {
requestId = getRequestId();
this.requestData = requestData;
this.rpcCallback = rpcCallback;
callbackName = CALLBACK_PREFIX + requestId;
addCallback(this, callbackName);
timeoutTimer = new Timer() {
@Override
public void run() {
timedOut = true;
cleanup();
notify.showError("Request timed out");
JsonpRequest.this.rpcCallback.onError(null);
}
};
}
private String getFullUrl(String rpcUrl) {
Map<String, String> arguments = new HashMap<String, String>();
arguments.put("callback", callbackName);
arguments.put("request", requestData);
return rpcUrl + "?" + Utils.encodeUrlArguments(arguments);
}
public void send(String rpcUrl) {
scriptTag = addScript(getFullUrl(rpcUrl), requestId);
timeoutTimer.schedule(REQUEST_TIMEOUT_MILLIS);
notify.setLoading(true);
}
public void cleanup() {
dropScript(scriptTag);
dropCallback(callbackName);
timeoutTimer.cancel();
notify.setLoading(false);
}
/**
* This method is called directly from native code (the dynamically loaded <script> calls
* our callback method, which calls this), so we need to do proper GWT exception handling
* manually.
*
* See the implementation of com.google.gwt.user.client.Timer.fire(), from which this
* technique was borrowed.
*/
@SuppressWarnings("unused")
public void handleResponse(JavaScriptObject responseJso) {
UncaughtExceptionHandler handler = GWT.getUncaughtExceptionHandler();
if (handler == null) {
handleResponseImpl(responseJso);
return;
}
try {
handleResponseImpl(responseJso);
} catch (Throwable throwable) {
handler.onUncaughtException(throwable);
}
}
public void handleResponseImpl(JavaScriptObject responseJso) {
cleanup();
if (timedOut) {
return;
}
JSONObject responseObject = new JSONObject(responseJso);
handleResponseObject(responseObject, rpcCallback);
}
}
public PaddedJsonRpcProxy(String rpcUrl) {
this.rpcUrl = rpcUrl;
}
private static int getRequestId() {
return idCounter++;
}
private static native void addCallback(JsonpRequest request, String callbackName) /*-{
window[callbackName] = function(someData) {
request.@autotest.common.PaddedJsonRpcProxy.JsonpRequest::handleResponse(Lcom/google/gwt/core/client/JavaScriptObject;)(someData);
}
}-*/;
private static native void dropCallback(String callbackName) /*-{
delete window[callbackName];
}-*/;
private static Element addScript(String url, int requestId) {
String scriptId = SCRIPT_TAG_PREFIX + requestId;
Element scriptElement = addScriptToDocument(scriptId, url);
return scriptElement;
}
private static native Element addScriptToDocument(String uniqueId, String url) /*-{
var elem = document.createElement("script");
elem.setAttribute("language", "JavaScript");
elem.setAttribute("src", url);
elem.setAttribute("id", uniqueId);
document.getElementsByTagName("body")[0].appendChild(elem);
return elem;
}-*/;
private static native void dropScript(Element scriptElement) /*-{
document.getElementsByTagName("body")[0].removeChild(scriptElement);
}-*/;
@Override
protected void sendRequest(JSONObject request, JsonRpcCallback callback) {
JsonpRequest jsonpRequest = new JsonpRequest(request.toString(), callback);
jsonpRequest.send(rpcUrl);
}
}