GWT RequestBuilder - 跨站点请求

Question

我正在尝试使用GWT请求构建器进行跨站点请求，但我还没有使其工作。正如您所看到的，这是一个GWT示例项目，并且我已经阅读了https://developers.google.com/web-toolkit/doc/latest/tutorial/Xsite。但我仍然缺少一些东西。

我在此处发布代码。我错过了什么..？

package com.gwt.reqbuilder.client;

import com.google.gwt.core.client.EntryPoint;
import com.google.gwt.http.client.Request;
import com.google.gwt.http.client.RequestBuilder;
import com.google.gwt.http.client.RequestCallback;
import com.google.gwt.http.client.RequestException;
import com.google.gwt.http.client.Response;
import com.google.gwt.http.client.URL;
import com.google.gwt.user.client.Window;

public class GWTRequestBuilder implements EntryPoint
{
    private static final String JSON_URL = "http://localhost:8000/?q=ABC&callback=callback125";
    public void onModuleLoad()
    {
        GWTPOSTHTTP();
    }

    public void GWTPOSTHTTP()
    {
        String postUrl="http://localhost:8000";
        String requestData="q=ABC&callback=callback125";
        RequestBuilder builder = new RequestBuilder(RequestBuilder.POST, postUrl);
        try {
            builder.sendRequest(requestData.toString(), new RequestCallback() 
            {
                public void onError(Request request, Throwable e) 
                {
                    Window.alert(e.getMessage());
                }
                public void onResponseReceived(Request request, Response response)
            {
                    if (200 == response.getStatusCode())
                    {
                        Window.alert(response.getText());
                    } else {
                        Window.alert("Received HTTP status code other than 200 : "+ response.getStatusText());
                    }
            }
            });
        } catch (RequestException e) {
            // Couldn't connect to server
        Window.alert(e.getMessage());
        }
    }
}

- Manikandaraj Srinivasan

Answer 1

实际上，如果我们可以在Servlet响应头中设置，就可以使用GWT RequestBuilder进行跨站请求。

Response.setHeader("Access-Control-Allow-Origin","http://myhttpserver");

很好，如果有人需要GWT项目和Python Servlet，请告诉我，我可以上传文件。

GWT Client Code : https://github.com/manikandaraj/MLabs/tree/master/GWT/GWTClient

- Manikandaraj Srinivasan

---

我一直在寻找这样的解决方案，我不想在GWT Java中使用本地JS。[抱歉jonasr，我真的很喜欢这个标题的想法] - Manikandaraj Srinivasan

Answer 2

您错过了完成教程的部分。

来自教程的直接引用：

RequestBuilder代码被getJson方法调用所替代。因此，在refreshWatchList方法中，您不再需要以下代码：

RequestBuilder builder = new RequestBuilder(RequestBuilder.GET, url);
try {
  Request request = builder.sendRequest(null, new RequestCallback() {
    public void onError(Request request, Throwable exception) {
      displayError("Couldn't retrieve JSON");
    }
 public void onResponseReceived(Request request, Response response) {
      if (200 == response.getStatusCode()) {
        updateTable(asArrayOfStockData(response.getText()));
      } else {
          displayError("Couldn't retrieve JSON (" + response.getStatusText()
            + ")");
      }
    }
  });
} catch (RequestException e) {
  displayError("Couldn't retrieve JSON");
}

这基本上是您拥有的内容，应该由教程中几行以下给出的JSNI函数替换：

  /**
   * Make call to remote server.
   */
  public native static void getJson(int requestId, String url,
      StockWatcher handler) /*-{
   var callback = "callback" + requestId;
// [1] Create a script element.
   var script = document.createElement("script");
   script.setAttribute("src", url+callback);
   script.setAttribute("type", "text/javascript");
// [2] Define the callback function on the window object.
   window[callback] = function(jsonObj) {
   // [3]
     [e-mail]::handleJsonResponse(Lcom/google/gwt/core/client/JavaScriptObject;)(jsonObj);
     window[callback + "done"] = true;
   }
...

- jonasr

---

我尝试了同样的事情，但对于某些链接有效，而对于其他一些链接则无效，您有任何想法吗？为什么有些网址不响应我。GWT获得成功响应，但在Firebug中响应为空白。可能是服务器问题吗？ - Mayank Pandya