Java 从 URLConnection 读取二进制文件
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Reading binary file from URLConnection
提问by Luke
I'm trying to read a binary file from a URLConnection. When I test it with a text file it seems to work fine but for binary files it doesn't. I'm using the following mime-type on the server when the file is send out:
我正在尝试从 URLConnection 读取二进制文件。当我用文本文件测试它时，它似乎工作正常，但对于二进制文件则不然。发送文件时，我在服务器上使用以下 MIME 类型：
application/octet-stream
But so far nothing seems to work. This is the code that I use to receive the file:
但到目前为止似乎没有任何效果。这是我用来接收文件的代码：
file = File.createTempFile( "tempfile", ".bin");
file.deleteOnExit();
URL url = new URL( "http://somedomain.com/image.gif" );
URLConnection connection = url.openConnection();
BufferedReader input = new BufferedReader( new InputStreamReader( connection.getInputStream() ) );
Writer writer = new OutputStreamWriter( new FileOutputStream( file ) );
int c;
while( ( c = input.read() ) != -1 ) {
writer.write( (char)c );
}
writer.close();
input.close();
采纳答案by ZZ Coder
This is how I do it,
我就是这样做的
input = connection.getInputStream();
byte[] buffer = new byte[4096];
int n;
OutputStream output = new FileOutputStream( file );
while ((n = input.read(buffer)) != -1)
{
output.write(buffer, 0, n);
}
output.close();
回答by Stephen C
If you are trying to read a binary stream, you should NOT wrap the InputStreamin a Readerof any kind. Read the data into a byte array buffer using the InputStream.read(byte[], int, int)method. Then write from the buffer to a FileOutputStream.
如果您尝试读取二进制流，则不应将InputStreama包装在Reader任何类型中。使用该InputStream.read(byte[], int, int)方法将数据读入字节数组缓冲区。然后从缓冲区写入FileOutputStream.
The way you are currently reading/writing the file will convert it into "characters" and back to bytes using your platform's default character encoding. This is liable to mangle binary data.
您当前读取/写入文件的方式将使用平台的默认字符编码将其转换为“字符”并返回到字节。这很容易损坏二进制数据。
(There is a charset (LATIN-1) that provides a 1-to-1 lossless mapping between bytes and a subset of the charvalue-space. However this is a bad idea even when the mapping works. You will be translating / copying the binary data from byte[]to char[]and back again ... which achieves nothing in this context.)
（有一个字符集（LATIN-1）提供字节和char值空间子集之间的一对一无损映射。但是，即使映射有效，这也是一个坏主意。您将翻译/复制二进制数据从byte[]到char[]和返回......在这种情况下什么也没有实现。）
