Cosmic Thoughts

Getting Started with Protocol Buffers

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What are Protocol Buffers?

From the Protobuf documentation:

  • Protocol buffers are Google’s language-neutral, platform-neutral, extensible mechanism for serializing structured data – think XML, but smaller, faster, and simpler.
  • You define how you want your data to be structured once, then you can use special generated source code to easily write and read your structured data to and from a variety of data streams and using a variety of languages.

Getting started

  1. Read the overview from here
  2. From here pick your favorite language.
  3. Follow the guide for your favorite language.

Example with Java

  1. Go to the Protocol Buffer Basics: Java page.
  2. The example, based from here, is a very simple address book application that can read and write people’s contact details to and from a file. Each person in the address book has a name, an ID, an email address, and a contact phone number.
  3. We need to start with a .proto file (e.g. addressbook.proto)
    • The one we are using for our example is here
    • Notice we are using proto3 syntax
  4. Generate the classes you’ll need to read and write your messages using the protocol buffer compiler protoc

    • If you haven’t installed the compiler, download the package and

      1. Unzip the file you downloaded and set it in a location where you want to install protoc
      2. Go to the folder and install the C++ Protocol Buffer runtime and the Protocol Buffer compiler (protoc) executing the following:
          $ ./configure
    $ make
    $ make check
    $ sudo make install
    $ sudo ldconfig # refresh shared library cache.

    • Once protoc is installed, run:

          protoc -I=$SRC_DIR --java_out=$DST_DIR $SRC_DIR/addressbook.proto

      where SRC_DIR is the source directory where your application’s source code lives and the DST_DIR is the destination directory, where you want the generated code to go.

      for example:

          protoc -I=/Users/username/dev/playing-with-protobuf/src/main/proto 
        --java_out=/Users/username/dev/playing-with-protobuf/src/main/java 
            /Users/username/dev/playing-with-protobuf/src/main/proto/addressbook.proto
  5. A new class named AddressBookProtos should be generated under the com.play.protobuf.gen package.
  6. Play around using the new class that was created, example here
  7. Next, play more! Write personal details to your address book file using the com.play.protobuf.AddPerson class.
    • Run it passing as param the path of your ADDRESS_BOOK_FILE
  8. Next, play more! Read the personal details from your address book file using the com.play.protobuf.ListPeople class.
    • Run it passing as param the path of your ADDRESS_BOOK_FILE
  9. Check out the Java API reference to see what else you can do with Protocol Buffers.
  10. To learn and know more about Protocol Buffers check the API Reference

All the code for this example is located here

References