Vaadin我在上传文件之前触发了addSucceededListener

问题描述

早上好，社区。我是Java和Vaadin的新手。请向我解释为什么addSucceededListener（）在下载文件之前（在加载页面时）被触发？

您可以在Vaadin论坛here上查看讨论。

只是一条鱼文本，它将省略编辑器以发布-_-

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@Route("")
public class UploadView extends VerticalLayout {
    @Autowired
    PictureRepository pictureRepository;

    @Autowired
    GoogleCloudAiAssistantRecognition googleCloudAiAssistantRecognition;

    public UploadView() {
        this.pictureRepository = pictureRepository;
        this.googleCloudAiAssistantRecognition = googleCloudAiAssistantRecognition;

        MenuBar menuBar = new MenuBar();
        menuBar.addThemeVariants(MenuBarVariant.LUMO_PRIMARY);

        MenuItem resultsItem = menuBar.addItem("Get Results");
        MenuItem tagItem = menuBar.addItem("Edit Tag");

        resultsItem.addClickListener(e -> UI.getCurrent().navigate("ai-result"));
        tagItem.addClickListener(e -> UI.getCurrent().navigate("edit-tag"));

        add(menuBar,new H1("Assistant recognition by Google Vision"));

        MemoryBuffer buffer = new MemoryBuffer();
        Upload upload = new Upload(buffer);
        upload.setAcceptedFileTypes("image/jpeg","image/png","image/gif");
        upload.setMaxFileSize(10485760);
        Div output = new Div();

        upload.addSucceededListener(event -> {
                InputStream inputStream = buffer.getInputStream();
                byte[] bytes = new byte[0];
                try {
                    bytes = IoUtils.toByteArray(inputStream);
                } catch (IOException e) {
                    e.printstacktrace();
                }

                add(new H1(event.getMIMEType()));
                Component component = createComponent(event.getMIMEType(),event.getFileName(),inputStream);
                showOutput(event.getFileName(),component,output);

                PictureModel pictureModel = new PictureModel(event.getFileName(),event.getMIMEType(),bytes);
                Long picId = pictureRepository.save(pictureModel).getId();

                List<TagModel> tags = null;
                try {
                    tags = googleCloudAiAssistantRecognition.detect(picId);
                } catch (Exception e) {
                    e.printstacktrace();
                }
                pictureModel.setTagModel(tags);
        });

        /*upload.getElement().addEventListener("upload-success",e -> {
            System.out.println(e.getEventData());
        });*/

        add(upload,output);
    }

解决方法

我怀疑您可能有误会。它添加了成功侦听器，但是侦听器代码尚未执行。

您似乎还使用了bytes变量，该变量始终为空，因为您读取了一个空缓冲区（在successedListener之外）的inputStream。

请尝试使用此代码，然后，如果您的“问题”仍然存在，请尝试重新制定问题。

public UploadView() throws IOException {
    add(new H1("Assistant recognition by Google Vision"));

    MemoryBuffer buffer = new MemoryBuffer();
    Upload upload = new Upload(buffer);
    upload.setAcceptedFileTypes("image/jpeg","image/png","image/gif");
    upload.setMaxFileSize(10485760);
    Div output = new Div();

    // move this INTO the succeededListener,because otherwise the buffer is empty
    //InputStream inputStream = buffer.getInputStream();
    //byte[] bytes = IOUtils.toByteArray(inputStream);

    upload.addSucceededListener(event -> {
        InputStream inputStream = buffer.getInputStream();
        byte[] bytes = IOUtils.toByteArray(inputStream);

        add(new H1(event.getMIMEType()));
        Component component = createComponent(event.getMIMEType(),event.getFileName(),inputStream);
        showOutput(event.getFileName(),component,output);

        PictureModel pictureModel = new PictureModel(event.getFileName(),event.getMIMEType(),bytes);
        Long picId = pictureRepository.save(pictureModel).getId();

        List<TagModel> tags = null;
        try {
            tags = googleCloudAiAssistantRecognition.detect(picId);
        } catch (Exception e) {
            e.printStackTrace();
        }
        pictureModel.setTagModel(tags);
        pictureRepository.save(pictureModel);
    });

    add(upload,output);
}