如何在内存中保存文件并读取文件输出流？

Question

File file = new File(filename);

new ByteArrayOutputStream(); 

public File file;

    public OutputStream receiveUpload(String filename,
                                      String mimeType) {

        // Create upload stream
        FileOutputStream fos = null; // Stream to write to
        file = null;

        if(StringUtils.containsIgnoreCase(filename, ".csv")){
            try {

                file = new File(filename);
                fos = new FileOutputStream(file);
            } catch (final java.io.FileNotFoundException e) {

                new Notification("Error", e.getMessage(), Notification.Type.WARNING_MESSAGE)
                    .show(Page.getCurrent());
                return null;
            }
        } else {

            new Notification("Document is not .csv file", Notification.Type.WARNING_MESSAGE)
                .show(Page.getCurrent());
            return null;
        }
        return fos; // Return the output stream to write to
    }

Answer 1

public OutputStream receiveUpload(String filename,
                                  String mimeType) {

    ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();

    return byteArrayOutputStream;
}

您可以使用以下方法获取在流中写入的内容：

byte[] dataWrittenInTheOutputStream = byteArrayOutputStream.toByteArray();

也可以将内容写入另一个OutputStream：

byteArrayOutputStream.writeTo(System.out);

或：

file = new File(filename);    
fos = new FileOutputStream(file);
byteArrayOutputStream.writeTo(fos);