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I've got bytes array in database.
How to extract file extension (mime/type) from byte array in java?
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Convert byte[] array to File using Java In order to convert a byte array to a file, we will be using a method named the getBytes() method of String class. Implementation: Convert a String into a byte array and write it in a file.
A byte is 8 bits (binary data). A byte array is an array of bytes (tautology FTW!). You could use a byte array to store a collection of binary data, for example, the contents of a file. The downside to this is that the entire file contents must be loaded into memory.
You can simply iterate the byte array and print the byte using System. out. println() method.
We can use String class getBytes() method to encode the string into a sequence of bytes using the platform's default charset. This method is overloaded and we can also pass Charset as argument. Here is a simple program showing how to convert String to byte array in java.
It turned out that there is a decent method in JDK's URLConnection class, please refer to the following answer: Getting A File's Mime Type In Java
If one needs to extract file extension from byte array instead of file, one should simply use java.io.ByteArrayInputStream (class to read bytes specifically from byte arrays) instead of java.io.FileInputStream (class to read bytes specifically from files) like in the following example:
byte[] content = ; InputStream is = new ByteArrayInputStream(content); String mimeType = URLConnection.guessContentTypeFromStream(is); //...close stream Hope this helps...
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If this is for storing a file that is uploaded:
If you don't have the original file, and you only have bytes, you have a couple of good solutions.
If you're able to use a library, look at using mime-util to inspect the bytes:
http://technopaper.blogspot.com/2009/03/identifying-mime-using-mime-util.html
If you have to build your own byte detector, here are many of the most popular starting bytes:
"BC" => bitcode, "BM" => bitmap, "BZ" => bzip, "MZ" => exe, "SIMPLE"=> fits, "GIF8" => gif, "GKSM" => gks, [0x01,0xDA].pack('c*') => iris_rgb, [0xF1,0x00,0x40,0xBB].pack('c*') => itc, [0xFF,0xD8].pack('c*') => jpeg, "IIN1" => niff, "MThd" => midi, "%PDF" => pdf, "VIEW" => pm, [0x89].pack('c*') + "PNG" => png, "%!" => postscript, "Y" + [0xA6].pack('c*') + "j" + [0x95].pack('c*') => sun_rasterfile, "MM*" + [0x00].pack('c*') => tiff, "II*" + [0x00].pack('c*') => tiff, "gimp xcf" => gimp_xcf, "#FIG" => xfig, "/* XPM */" => xpm, [0x23,0x21].pack('c*') => shebang, [0x1F,0x9D].pack('c*') => compress, [0x1F,0x8B].pack('c*') => gzip, "PK" + [0x03,0x04].pack('c*') => pkzip, "MZ" => dos_os2_windows_executable, ".ELF" => unix_elf, [0x99,0x00].pack('c*') => pgp_public_ring, [0x95,0x01].pack('c*') => pgp_security_ring, [0x95,0x00].pack('c*') => pgp_security_ring, [0xA6,0x00].pack('c*') => pgp_encrypted_data, [0xD0,0xCF,0x11,0xE0].pack('c*') => docfile If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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