Java Wicket AjaxLink和RequestHandler-如何？

使用场景：用户点击网站上的一个链接，就会得到动态生成的德语和英语两种语言的PDF。

此代码可以工作。GenerateCouponPdfOnClick创建包含PDF文件的ResourceStreamRequestHandler。

Link<Void> generatePdf = new Link<Void>("generatePdf") {
@Override
public void onClick() {
    ResourceStreamRequestHandler requestHandler = generateCouponPdfOnClick(coupon, PDFLanguage.GERMAN);
    getRequestCycle().scheduleRequestHandlerAfterCurrent(requestHandler);
}
};

现在我想更改代码以获得弹出窗口(Wicket ModalWindow，这里的类为PdfDialogPage)，用户可以通过点击两个按钮中的一个来选择PDF的语言(德语/英语)。如果用户单击按钮，则应该关闭ModalWindow，并且应该生成并显示PDF。

以下是修改后的代码：变量pdflanguageanguage包含选定的语言，由PdfDialogPage使用PageReferenz设置

AjaxLink<Void> generatePdf = new AjaxLink<Void>("generatePdf") {
@Override
public void onClick(final AjaxRequestTarget target) {
    modalWindow.setPageCreator(() -> {
        return new PdfDialogPage(getPage().getPageReference(), modalWindow);
    });
    modalWindow.setWindowClosedCallback((AjaxRequestTarget target1) -> {
        ResourceStreamRequestHandler requestHandler = generateCouponPdfOnClick(coupon, pdflanguageanguage);
        getRequestCycle().scheduleRequestHandlerAfterCurrent(requestHandler);
    });
    modalWindow.show(target);
};

当我单击该链接时，将打开modal窗口。我选择语言，例如英语，在将"English"写入变量pdflanguageanguage时，modalWindow关闭。总比什么都没发生要好。并且不会生成该PDF。Wicket AJAX调试窗口告诉我以下日志：

</head>]]></header-contribution><evaluate><![CDATA[(function(){var settings = {"minWidth":200,"minHeight":200,"className":"w_blue","width":400,"height":100,"resizable":true,"src":"./wicket/page?6","mask":"semi-transparent","autoSize":false,"unloadConfirmation":true,"onClose":function() { Wicket.Ajax.ajax({"u":"./overviewCoupons?5-1.1-panel-modalWindow","c":"modalWindowb0"}); },"onCloseButton":function() { Wicket.Ajax.ajax({"u":"./overviewCoupons?5-1.0-panel-modalWindow","c":"modalWindowb0"});; return false; }};window.setTimeout(function(){
  Wicket.Window.create(settings).show();
}, 0);
})();]]></evaluate></ajax-response>
INFO: returned focused element: javascript:;
INFO: returned focused element: javascript:;
INFO: Response processed successfully.
INFO: refocus last focused component not needed/allowed
INFO: focus removed from generatePdf5
INFO: focus set on _wicket_window_3
INFO: focus set on undefined
INFO: focus removed from undefined

ERROR: Wicket.Ajax.Call.failure: Error while parsing response: Error: Invalid XML: %PDF-1.4
%����

1 0 obj
<<
/Creator (Apache FOP Version 2.3)
/Producer (Apache FOP Version 2.3)
/CreationDate (D:20180808160110+02'00')

我认为AJAX和"getRequestCycle().scheduleRequestHandlerAfterCurrent(requestHandler)；".之间存在问题我如何将它们一起使用。因此我将代码减少为：

AjaxLink<Void> generatePdf = new AjaxLink<Void>("generatePdf") {
@Override
public void onClick(final AjaxRequestTarget target) {
ResourceStreamRequestHandler requestHandler = generateCouponPdfOnClick(coupon, PDFLanguage.ENGLISH);
getRequestCycle().scheduleRequestHandlerAfterCurrent(requestHandler);
}
};

当我知道单击AjaxLink时，什么也不会发生，但我得到相同的AJAX日志错误输出。

如何将AjaxLink与ResourceStreamRequestHandler一起使用？

---

解决方案

我用这种方式解决了一个与您类似的用例。

您需要here中的Java类AjaxDownload

或者，您也可以使用My Variant，它接受FileResourceStream作为输入。

import lombok.extern.slf4j.Slf4j;
import org.apache.wicket.ajax.AjaxRequestTarget;
import org.apache.wicket.behavior.AbstractAjaxBehavior;
import org.apache.wicket.request.handler.resource.ResourceStreamRequestHandler;
import org.apache.wicket.request.resource.ContentDisposition;
import org.apache.wicket.util.resource.FileResourceStream;

/**
 * @author Sven Meier
 * @author Ernesto Reinaldo Barreiro (reiern70@gmail.com)
 * @author Jordi Deu-Pons (jordi@jordeu.net)
 */
@Slf4j
public class AJAXDownload extends AbstractAjaxBehavior {

    private boolean addAntiCache;
    private FileResourceStream fileResourceStream;
    private String fileName;

    public AJAXDownload() {
        this(true);
    }

    public AJAXDownload(boolean addAntiCache) {
        super();
        this.addAntiCache = addAntiCache;
    }

    /**
     * Call this method to initiate the download.
     */
    public void initiate(AjaxRequestTarget target, FileResourceStream fileResourceStream, String fileName) {
        this.fileResourceStream= fileResourceStream;
        this.fileName = fileName;
        String url = getCallbackUrl().toString();

        if (addAntiCache) {
            url = url + (url.contains("?") ? "&" : "?");
            url = url + "antiCache=" + System.currentTimeMillis();
        }

        // the timeout is needed to let Wicket release the channel
        target.appendJavaScript("setTimeout("window.location.href='" + url + "'", 100);");
    }

    public void onRequest() {
        try{
            ResourceStreamRequestHandler handler = new ResourceStreamRequestHandler(fileResourceStream, fileName);
            handler.setContentDisposition(ContentDisposition.ATTACHMENT);
            getComponent().getRequestCycle().scheduleRequestHandlerAfterCurrent(handler);
        } catch (Exception e){
            log.error("Error while trying to download", e);
            onErrorOccurred();
        }
    }
    protected void onErrorOccurred(){}
}

如何使用？

1. 您必须将AjaxDownload添加到您的表单

   form.add(ajaxDownload = new AJAXDownload());
   

2. 在通过AjaxLink提交的onSubmit中，您可以调用：

   File yourPdfFile = //create your pdf file;
   final FileResourceStream resourceStream= new FileResourceStream(yourPdfFile);
   ajaxDownload.initiate(target, resourceStream, "yourPDF.pdf");