java中的简单流读/写问题 [英] Simple stream read/write question in java

问题描述

我正在尝试通过URLConnection上传文件，但我需要将其作为二进制文件读/写而不进行任何编码更改。

I'm trying to upload a file via URLConnection, but I need to read/write it as a binary file without any encoding changes.

所以我已经试图从 FileInputStream 中读取 byte [] 数组，但现在我遇到了问题。我用来输出到服务器的 PrintWriter 对象不允许我做 writer.write（content）（其中 content 的类型为 byte [] ）。我怎样才能解决这个问题？或者是否有另一种方法可以快速将二进制数据从 FileInputStream 复制到 PrintWriter ？

So i've tried to read byte[] array from a FileInputStream, but now i have an issue. The PrintWriter object I use for outputing to the server does not allow me to do writer.write(content) (where content is of type byte[]). How can i fix this? Or is there another way to quickly copy binary data from a FileInputStream to a PrintWriter?

谢谢

推荐答案

Writer 对象（包括 PrintWriter ）专门用于输出字符数据。听起来你想要一个 OutputStream 而不是 Writer 这里。

你的 PrintWriter 来自哪里？如果它是通过使用 OutputStreamWriter 包装某种 OutputStream 创建的，然后使用 PrintWriter ，那么你应该只使用原来的 OutputStream中的原始 write（byte [] b）方法，而不是尝试使用 Writer 。

Where did your PrintWriter come from? If it was created by wrapping some kind of OutputStream with an OutputStreamWriter and then wrapping that with a PrintWriter, then you should just use the original write(byte[] b) method from the original OutputStream, rather than trying to use a Writer.

如果你想混合字符输出和字节输出，您可能需要使用 String.getBytes（） 。看看这个例子：

If you want to mix character output and byte output, you may need to use String.getBytes(). Check out this example:

OutputStream o = this.conn.getOutputStream(); // Based on your comment
String s = "Hello, world!";
byte[] b = ...;      // These are the raw bytes that you want to write
o.write(s.getBytes("UTF-8"));
o.write(b);

（当然，只有在阅读输出的系统明白您正在撰写时，这才有效字符和原始字节的混合，并知道如何处理您发送它的混合数据。）

(Of course, this will only work if the system that is reading your output understands that you are writing a mixture of characters and raw bytes and knows how to handle the mixed data that you are sending it.)

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