GWT同步呼叫 [英] GWT Synchronous call

问题描述

我有一个GWT中的方法，它使用请求的fire方法从数据库中检索数据，因为你们都知道它的异步方式，我从JS调用这个方法，所以我需要使它成为同步的

  private static String retriveLocation（String part）
 {
 ClientFactory clientFactory = GWT.create（ ClientFactory.class）; 
 MyRequestFactory requestFactory = clientFactory.getRequestFactory（）; 
 YadgetRequest request = requestFactory.yadgetRequest（）; 
 String criteria =！ +部分; 
 final ArrayList< String> tags = new ArrayList< String>（）; 
 
 request.getTagsStartingWith（criteria，10，0）.fire（
 new Receiver< List< TagProxy>>（）{
 @Override 
 public void onSuccess （List< TagProxy> tagList）{
 String output =[; 
 
 for（TagProxy pt：tagList）{
 output + ={; 
输出+ =\id \：+\+ pt.getId（）+\，; 
 output + =\value \： 
 +\
 + pt.getName（）。replaceAll（\，）
 .replaceAll（！，）+\ ; 
 output + =}，; 
 
} 
 if（output.length（）> 2）
 output = output.substring（0 ，output.length（） -  1）; 
 output + =] ; 
 tags.add（output）; 
 
} 
 
 @Override 
 public void onFailure（ServerFailure error）{
 
 
 $ b $} ; 
 
返回tags.size（）+; 
 
 
 $ / code> 

并且像这样从JS中调用这个函数：

  public static native export exportStaticMethod（）/ *  -  {
 $ wnd.computeLoanInterest = 
 $ wnd.getAutocomplete =@com.yadget.client.Yadget :: retriveLocation（Ljava / lang / String;）; 
}  -  * /; 
  

和里面 onModuleLoad（） code> exportStaticMethod（）。

和html我有一个按钮，我调用onclick getAutocomplete（） >像这样：

$ b

 < input type =buttononclick =alert（getAutocomplete（'j'））value =momo/> 
  

问题是大小始终返回0，因为该方法是异步的，但如果我可以返回值 onSuccess 这将解决我的问题。请有任何想法吗？我已经使用Google搜索了2天并没有得到任何答案。换句话说：

我有JS方法我需要它调用java方法来从数据库检索数据，但同步！

示例

如果我有一个HTML按钮，点击后我会将ID传递给一个函数，通过GWT从DB中检索名称并提醒它;只是因为GWT是异步的，我不能每次都这样做，当我提醒结果时，它将是一个空的，因为它还没有被填充。

解决方案

不能同步使用本地GWT RPC。
我不确定这是你所问的，但是这里是如何同步调用服务器：

  private native String makeSyncAjaxCall（String url，String msgText，String conType）/ *  -  {
 var xhReq = new XMLHttpRequest（）; 
 xhReq.open（conType，url，false）; 
 if（conType ==POST）xhReq.setRequestHeader（'Content-Type'，'application / x-www-form-urlencoded'）; 
 xhReq.send（msgText）; 
 var serverResponse = xhReq.status + xhReq.responseText; 
返回serverResponse; 
}  -  * /; 
  

请注意，我并不是在讨论这是不是个好主意。您应该坚持使用Async并将警报放在成功事件中。

I have a method in GWT which retrieves the DATA from the DB using the fire method of the requests as you all know its asynchronous I am calling this method from JS so I need to make synchronous is it possible

private static String retriveLocation(String part)
{
    ClientFactory clientFactory = GWT.create(ClientFactory.class);
    MyRequestFactory requestFactory = clientFactory.getRequestFactory();
    YadgetRequest request = requestFactory.yadgetRequest();
    String criteria = "!" + part;
    final ArrayList<String> tags = new ArrayList<String>();

    request.getTagsStartingWith(criteria, 10, 0).fire(
            new Receiver<List<TagProxy>>() {
                @Override
                public void onSuccess(List<TagProxy> tagList) {
                    String output = "[";

                    for (TagProxy pt : tagList) {
                        output += "{";
                        output += "\"id\":" + "\"" + pt.getId() + "\",";
                        output += "\"value\":"
                                + "\""
                                + pt.getName().replaceAll("\"", "")
                                        .replaceAll("!", "") + "\"";
                        output += "},";

                    }
                    if (output.length() > 2)
                        output = output.substring(0, output.length() - 1);
                    output += "]";
                    tags.add(output);

                }

                @Override
                public void onFailure(ServerFailure error) {

                }

            });

    return tags.size() + "";

}

and calling this function from JS like this:

public static native void exportStaticMethod() /*-{
    $wnd.computeLoanInterest =
    $wnd.getAutocomplete =@com.yadget.client.Yadget::retriveLocation(Ljava/lang/String;);
}-*/;

and inside onModuleLoad() I call exportStaticMethod().

and in html I have a button I call onclick getAutocomplete() like this:

<input type="button" onclick="alert(getAutocomplete('j'))" value="momo" /> 

The problem is that the size always returns 0 because the method is asynchronous but if I could return the value onSuccess that would solve my problem. Any ideas please? I have been googling it for 2 days and got no answer.

In other words:

I have JS method I need it to call java method to retrieve data from DB but synchronously!

Example

If I have an HTML button and on click I will pass ID to a function and I need to retrive the name from the DB via GWT and alert it; simply because GWT is asyncronous, I wont be able to do so everytime and when I alert the result, it will be an empty because it's not filled yet.

解决方案

You cannot use the native GWT RPC synchronously. I am not sure that this is what you are asking, but here is how to make a call to the server synchronously:

private native String makeSyncAjaxCall(String url, String msgText, String conType)/*-{
    var xhReq = new XMLHttpRequest();
    xhReq.open(conType, url, false);
    if(conType == "POST") xhReq.setRequestHeader('Content-Type','application/x-www-form-urlencoded');
    xhReq.send(msgText);
    var serverResponse = xhReq.status + xhReq.responseText;
    return serverResponse;
}-*/; 

Please note that I am not discussing whether that is good idea or not. You should probably stick with Async and put the alert on the success event.

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