我正在尝试使用java.net.Socket
不带java.net.URL
外部库的图像进行下载。这是我所拥有的,我不确定什么不起作用。
String domain = "www.manchester.edu";
String path = "/images/default-source/default-album/slide1.jpg";
Socket socket = new Socket(domain,80);
PrintWriter out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(socket.getOutputStream())));
out.println("" +
"Get "+path+" HTTP/1.1\n" +
"Host: "+domain+"\n"+
"");
out.println();
out.flush();
BufferedImage image = ImageIO.read(socket.getInputStream());
为了查看流中正在发生的事情,请将该BufferedImage
行交换为:
BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
String inputLine;
while ((inputLine = in.readLine()) != null && inputLine.trim() != "0") {
System.out.println(inputLine);
}
大概该ImageIO.read(...)
方法在套接字输入流中不希望使用HTTP标头。但是我不确定如何删除标题。我试着用读取标题行,BufferedReader
然后将套接字输入流传递给,ImageIO.read(...)
但这没有用。
这是打印的字符串BufferedReader
:
HTTP/1.1 200 OK
Cache-Control: public, max-age=7776000
Content-Length: 96876
Content-Type: image/jpeg
Expires: Thu, 04 Feb 2016 21:36:46 GMT
Last-Modified: Tue, 15 Sep 2015 14:23:40 GMT
Server: Microsoft-IIS/8.5
content-disposition: inline; filename=slide1.jpg
X-AspNet-Version: 4.0.30319
X-Powered-By: ASP.NET
Date: Fri, 06 Nov 2015 21:36:46 GMT
����...
末尾的不可打印字符似乎表明标题之后是某种图像。但是如何将其转换为ajava.awt.image.BufferedImage
或a javafx.scene.image.Image
?后者有一个接受输入流的构造函数,我已经尝试过了,但是它不起作用(因为http标头?)。这个问题与此类似,但是我试图创建一个图像而不是一个文件。
使用BufferedReader
有误,原因有两个:
String
,然后再转换回字节以将其发送到输出流。转换可能(并且可能会)导致数据丢失;您需要通过手术来解决此问题,创建一个所需大小的字节缓冲区,并使用anInputStream
根据自己的条件逐字节读取流。另外,由于您知道HTTP标头的结尾为“ \ r \ n \ r \ n”(或13 10 13 10字节),因此可以扫描自己的缓冲区以查找此模式并采取相应的措施。
最好的选择是将图像下载到文件中,然后使用ImageIO从本地文件中读取图像。
// Initialize the streams.
final FileOutputStream fileOutputStream = new FileOutputStream(file);
final InputStream inputStream = socket.getInputStream();
// Header end flag.
boolean headerEnded = false;
byte[] bytes = new byte[2048];
int length;
while ((length = inputStream.read(bytes)) != -1) {
// If the end of the header had already been reached, write the bytes to the file as normal.
if (headerEnded)
fileOutputStream.write(bytes, 0, length);
// This locates the end of the header by comparing the current byte as well as the next 3 bytes
// with the HTTP header end "\r\n\r\n" (which in integer representation would be 13 10 13 10).
// If the end of the header is reached, the flag is set to true and the remaining data in the
// currently buffered byte array is written into the file.
else {
for (int i = 0; i < 2045; i++) {
if (bytes[i] == 13 && bytes[i + 1] == 10 && bytes[i + 2] == 13 && bytes[i + 3] == 10) {
headerEnded = true;
fileOutputStream.write(bytes, i+4 , 2048-i-4);
break;
}
}
}
}
inputStream.close();
fileOutputStream.close();
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