我有来自 UploadedFile 按钮的文件,我想使用魔数(Magic Number)打印扩展文件,
我的代码:
UploadedFile file = (UploadedFile)valueChangeEvent.getNewValue();
byte[] fileByteArray = IOUtils.toByteArray(file.getInputStream());
注意:Mime 类型和内容文件(来自文件和来自文件名)与魔数(Magic Number)不同(魔数(Magic Number)来自 inputStream 的第一个字节)
我该怎么做?
最佳答案
我知道这是一个老问题,只需将我的答案放在这里,希望有人在搜索相同的解决方案时发现它很有用。
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.Part;
import javax.servlet.annotation.MultipartConfig;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
@MultipartConfig(
fileSizeThreshold = 0,
maxFileSize = 1024 * 1024 * 50, // 50MB
maxRequestSize = 1024 * 1024 * 100) // 100MB
public class FileUpload extends HttpServlet {
private static final Logger logger = LogManager.getLogger(FileUpload.class);
private byte[] data = new byte[4];
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws IOException, ServletException {
response.setContentType("text/plain");
response.setCharacterEncoding("UTF-8");
try {
fileSignature(request
.getPart("image_file")
.getInputStream());
} catch (IOException | NullPointerException ex) {
logger.error(ex);
}
String fileType = getFileType(data);
// return the recognized type
response.getWriter().write(fileType);
}
/**
* Get the first 4 byte of a file file signature.
*
* @param part File from part.
*/
private void fileSignature(InputStream is)
throws IOException, NullPointerException {
is.read(data, 0, 4);
}
/**
* Get the file type based on the file signature.
* Here restricted to only recognized file type jpeg, jpg, png and
* pdf where the signature of jpg and jpeg files are the same.
*
* @param fileData Byte array of the file.
* @return String of the file type.
*/
private String getFileType(byte[] fileData) {
String type = "undefined";
if(Byte.toUnsignedInt(fileData[0]) == 0x89 && Byte.toUnsignedInt(fileData[1]) == 0x50)
type = "png";
else if(Byte.toUnsignedInt(fileData[0]) == 0xFF && Byte.toUnsignedInt(fileData[1]) == 0xD8)
type = "jpg";
else if(Byte.toUnsignedInt(fileData[0]) == 0x25 && Byte.toUnsignedInt(fileData[1]) == 0x50)
type = "pdf";
return type;
}
}
文件魔数(Magic Number)引用:
关于java - 如何从java中的文件中获取魔数(Magic Number),我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/41206540/