How to reliably determine file types?

Question

Purpose: This file determines if the given type (XML, JSON, properties, etc.)

Consider the XML-Up case, until we ran into this problem, the following sample approach worked fine:

try { saxReader.read(f); } catch (DocumentException e) { logger.warn(" - File is not XML: " + e.getMessage()); return false; } return true; 

As expected, when the XML is well-formed, the test passes and the method returns true. If something bad happens and the file cannot be parsed, false is returned.

This violates, however, when we are dealing with malformed XML (still an XML file).

I would rather not rely on the .xml extension (doesn't work all the time), look for the string <?xml version="1.0" encoding="UTF-8"?> Inside the file, etc.

Is there any other way to handle this?

What would you see inside the file to "suspect that it might be XML , although DocumentException been caught." This is necessary for parsing.

Answer 1

File Type Detection Tools:

• Mime Detection Utility
• DROID (digital recording object identification)
• ftc - File Type Classifier
• JHOVE , JHOVE2
• NLNZ Metadata Extraction Tool
• Apache tika
• TrID , TrIDNet
• Oracle Outside In (commercial)
• Forensic research tool to scan files TOOLS (commercial)

Answer 2

Apache Tika gives me the least amount of problems and is not platform specific unlike Java 7: Files.probeContentType

 import java.io.File; import java.io.IOException; import javax.activation.MimeType; import org.apache.tika.Tika; File inputFile = ... String type = new Tika().detect(inputFile); System.out.println(type); 

For xml file, I got 'application / xml'

for the properties file I got "text / plain"

However, you can add a detector to the new Tika ()

 <dependency> <groupId>org.apache.tika</groupId> <artifactId>tika-core</artifactId> <version>1.xx</version> </dependency> 

Answer 3

For those who do not need very accurate detection ( Java 7 Files.probeContentType method mentioned by rjdkolb)

 Path filePath = Paths.get("/path/to/your/file.jpg"); String contentType = Files.probeContentType(filePath);