Adam Cozzette
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README.md
Protocol Buffers - Google's data interchange format
Copyright 2008 Google Inc.
This directory contains the JavaScript Protocol Buffers runtime library.
The library is currently compatible with:
- CommonJS-style imports (eg.
var protos = require('my-protos');
) - Closure-style imports (eg.
goog.require('my.package.MyProto');
)
Support for ES6-style imports is not implemented yet. Browsers can be supported by using Browserify, webpack, Closure Compiler, etc. to resolve imports at compile time.
To use Protocol Buffers with JavaScript, you need two main components:
- The protobuf runtime library. You can install this with
npm install google-protobuf
, or use the files in this directory. If npm is not being used, as of 3.3.0, the files needed are located in binary subdirectory; arith.js, constants.js, decoder.js, encoder.js, map.js, message.js, reader.js, utils.js, writer.js - The Protocol Compiler
protoc
. This translates.proto
files into.js
files. The compiler is not currently available via npm, but you can download a pre-built binary on GitHub (look for theprotoc-*.zip
files under Downloads).
Setup
First, obtain the Protocol Compiler. The easiest way is to download a pre-built binary from https://github.com/protocolbuffers/protobuf/releases.
If you want, you can compile protoc
from source instead. To do this
follow the instructions in the top-level
README.
Once you have protoc
compiled, you can run the tests by typing:
$ cd js
$ npm install
$ npm test
# If your protoc is somewhere else than ../src/protoc, instead do this.
# But make sure your protoc is the same version as this (or compatible)!
$ PROTOC=/usr/local/bin/protoc npm test
This will run two separate copies of the tests: one that uses
Closure Compiler style imports and one that uses CommonJS imports.
You can see all the CommonJS files in commonjs_out/
.
If all of these tests pass, you know you have a working setup.
Using Protocol Buffers in your own project
To use Protocol Buffers in your own project, you need to integrate the Protocol Compiler into your build system. The details are a little different depending on whether you are using Closure imports or CommonJS imports:
Closure Imports
If you want to use Closure imports, your build should run a command like this:
$ protoc --js_out=library=myproto_libs,binary:. messages.proto base.proto
For Closure imports, protoc
will generate a single output file
(myproto_libs.js
in this example). The generated file will goog.provide()
all of the types defined in your .proto files. For example, for the unit
tests the generated files contain many goog.provide
statements like:
goog.provide('proto.google.protobuf.DescriptorProto');
goog.provide('proto.google.protobuf.DescriptorProto.ExtensionRange');
goog.provide('proto.google.protobuf.DescriptorProto.ReservedRange');
goog.provide('proto.google.protobuf.EnumDescriptorProto');
goog.provide('proto.google.protobuf.EnumOptions');
The generated code will also goog.require()
many types in the core library,
and they will require many types in the Google Closure library. So make sure
that your goog.provide()
/ goog.require()
setup can find all of your
generated code, the core library .js
files in this directory, and the
Google Closure library itself.
Once you've done this, you should be able to import your types with statements like:
goog.require('proto.my.package.MyMessage');
var message = proto.my.package.MyMessage();
If unfamiliar with Closure or its compiler, consider reviewing Closure documentation https://developers.google.com/closure/library/docs/tutorial https://developers.google.com/closure/library/docs/closurebuilder https://developers.google.com/closure/library/docs/depswriter At a high level, closurebuilder.py can walk dependencies, and compile your code, and all dependencies for Protobuf into a single .js file. Using depsbuilder.py to generate a dependency file can also be considered for non-production dev environments.
CommonJS imports
If you want to use CommonJS imports, your build should run a command like this:
$ protoc --js_out=import_style=commonjs,binary:. messages.proto base.proto
For CommonJS imports, protoc
will spit out one file per input file
(so messages_pb.js
and base_pb.js
in this example). The generated
code will depend on the core runtime, which should be in a file called
google-protobuf.js
. If you are installing from npm
, this file should
already be built and available. If you are running from GitHub, you need
to build it first by running:
$ gulp dist
Once you've done this, you should be able to import your types with statements like:
var messages = require('./messages_pb');
var message = new messages.MyMessage();
The --js_out
flag
The syntax of the --js_out
flag is:
--js_out=[OPTIONS:]output_dir
Where OPTIONS
are separated by commas. Options are either opt=val
or
just opt
(for options that don't take a value). The available options
are specified and documented in the GeneratorOptions
struct in
src/google/protobuf/compiler/js/js_generator.h.
Some examples:
--js_out=library=myprotos_lib.js,binary:.
: this contains the optionslibrary=myprotos.lib.js
andbinary
and outputs to the current directory. Theimport_style
option is left to the default, which isclosure
.--js_out=import_style=commonjs,binary:protos
: this contains the optionsimport_style=commonjs
andbinary
and outputs to the directoryprotos
.import_style=commonjs_strict
doesn't expose the output on the global scope.
API
The API is not well-documented yet. Here is a quick example to give you an idea of how the library generally works:
var message = new MyMessage();
message.setName("John Doe");
message.setAge(25);
message.setPhoneNumbers(["800-555-1212", "800-555-0000"]);
// Serializes to a UInt8Array.
var bytes = message.serializeBinary();
var message2 = MyMessage.deserializeBinary(bytes);
For more examples, see the tests. You can also look at the generated code to see what methods are defined for your generated messages.