Protocol Buffers to file?

Question

I am new to Protocol Buffers and seeing this as good approach to go. I created a proto file, and using compiler, I generated Java beans.

Using this Java Beans, I initialize the object, and try to write it to file. The purpose is just to see how big the file is. I don't have client/server test ready at this moment to test via HTTP. I am just trying to show my team at this point, how the request/response look like using protocol buffers.

Code I have is something like this:

=== Proto file ===

Profile {
  optional string name=1
  optional string id=2

  message DocGuids {
     required string docguids=3
  }

  repeated DocGuids docguids=4
}

=== Sample code ===

ProfileRequest.Builder profile = ProfileRequest.newBuilder();
profile.setName("John");
profile.setId("123");

for (int i=0;i<10;i++) {
 ProfileRequest.DocGuids.Builder docGuids = ProfileRequest.DocGuids.newBuilder();
 docGuids.setDocguid(GUID.guid()); 
     profile.addDocguids(docGuids);   
}

//write to disk
try {
    // Write the new address book back to disk.
   FileOutputStream output = new FileOutputStream("c:\\testProto.txt");
   DataOutputStream dos = new DataOutputStream(output);                  
       dos.write(profile.build().toByteArray());     
   dos.close();
   output.close();   
} catch (Exception e) {   
}

When I check testProto.txt, I saw the file was written as text file, not binary file, eventhough I use toByteArray.

Anyone could help?

Thanks

By the way, this is the code to read this file:

// Read from disk
FileInputStream input = new FileInputStream("c:\\testProto.txt");
DataInputStream dis = new DataInputStream(input);
profileBuild.mergeFrom(dis);
dis.close();
input.close()

I am able to read the object and get the value just fine, but just wondering if this is the correct approach to do?

score 2 · Accepted Answer · answered Jun 22 '10 at 14:59

2

I'm not sure why you're creating the DataOutputStream and calling dos.write in the first place...

I would normally use this:

profile.build().writeTo(output);

However, I would still have expected the file to be a binary file really. Sure, it would include the text "123" and "John" as those are just UTF-8 strings... but there should have been non-text in there as well. Are you sure it's just text? Could you post the output?

answered Jun 22 '10 at 14:59

Jon Skeet

1,421,763
867
9,128
9,194

Here is the ouput: 123John# !i0ad0290e000001296033cf0b540e7ae7# !i0ad0290e000001296033cf0b540e7ae8# Alhtough in before and after 123(and John), there is some weird character in my TextPad which I am not able to copy here. I am thinking it might be "tab" character – user373307 Jun 22 '10 at 15:11
2

@workrelated: I suggest you look at the file in a hex editor. Just because a file has recognisable text in doesn't mean it's a text file. Have a look at it in conjunction with the pb format spec. – Jon Skeet Jun 22 '10 at 15:19
Thanks Jon. I update the question above with my sample code of reading that file. Is that a right approach to do? – user373307 Jun 22 '10 at 15:23
@workrelated: Again, why are you using a `DataInputStream`? Just merge straight from the `FileInputStream`. See the address book example for sample code. – Jon Skeet Jun 22 '10 at 15:28
I could verify the protobuf serialized data using `xxd serialized-file.bin`. You can also see serialized data in Hex editor https://github.com/HexFiend/HexFiend. See https://stackoverflow.com/questions/827326/whats-a-good-hex-editor-viewer-for-the-mac – prayagupa Dec 29 '22 at 22:44

Protocol Buffers to file?

1 Answers1