java如何保存上传的文件

Question

我想知道如何从Vaadin上传组件获取文件。下面是关于Vaadin Website的例子 但除了OutputStreams之外，它不包括如何保存它。 救命

Answer 1

要在Vaadin中接收文件上载，必须实现Receiver接口，该接口为您提供receiveUpload(filename, mimeType)方法，用于接收信息。实现这一点的最简单代码是（以Vaadin 7 docs为例）：

class FileUploader implements Receiver {
    private File file;
    private String BASE_PATH="C:\";

    public OutputStream receiveUpload(String filename,
                                  String mimeType) {
        // Create upload stream
        FileOutputStream fos = null; // Stream to write to
        try {
            // Open the file for writing.
            file = new File(BASE_PATH + filename);
            fos = new FileOutputStream(file);
        } catch (final java.io.FileNotFoundException e) {
            new Notification("Could not open file<br/>",
                         e.getMessage(),
                         Notification.Type.ERROR_MESSAGE)
            .show(Page.getCurrent());
            return null;
        }
        return fos; // Return the output stream to write to
    }
};

这样，Uploader将在C:\中为您编写一个文件。如果您希望在上传成功或失败后完成某些操作，可以实现SucceeddedListener或FailedListener。以上面的例子为例，结果（带有SucceededListener）可能是：

class FileUploader implements Receiver {
    //receiveUpload implementation

    public void uploadSucceeded(SucceededEvent event) {
        //Do some cool stuff here with the file
    }
}