环境：ubuntu_server 1210
目的：构建web版hello world程序
1.使用rebar 构建一个项目的基础目录
首先获取rebar工具
$ git clone https://github.com/rebar/rebar.git
$ cd rebar
$ ./bootstrap
$ cd ..
Initialize a new git repository and use rebar to create the skeleton for a new Erlang app. I decided to call my application erlblog. Call your application differently, replacing every occurrence of erlblog with your favourite application name in the instructions below. Please note that this is not optional, since two applications cannot have the same name on Heroku and you don’t dare to * with my own application.
创建一个目录erlblog
将rebar编译好并生成的可执行文件rebar复制到erlblog目录,执行以下命令生成项目基础目录
$ ./rebar create-app appid=erlblog
生成rebar需要的配置文件，名字必须为rebar.config
$ cat rebar.config
配置文件内容如下：
{deps, [
{cowboy, "0.8.4", {git, "https://github.com/extend/cowboy.git", {tag, "0.8.4"}}}
]}.
Add cowboy to the list of applications in your .app.src file. Also, set the http_port environment variable to 8080 (see next paragraphs).
在erlblog 目录的src目录下生成erlblog配置文件，erlang虚拟机根据此文件启动应用程序
$ cat src/erlblog.app.src
文件内容：
{application, erlblog,
[
{description, ""},
{vsn, "1"},
{registered, []},
{applications, [
kernel,
stdlib,
cowboy
]},
{mod, { erlblog_app, []}},
{env, [{http_port, 8080}]}
]}.
修改erlblog_app.erl文件的start/2函数，当erlblog应用程序启动时Cowboy才能启动一个进程池，接收用户连接
配置Cowboy路由分派器为一个单一的路径，所有的请求都路由到根路径"/",并使用erlblog_handler处理用户请求
修改模块内容：
$ cat src/erlblog_app.erl
-module(erlblog_app).
-behaviour(application).
%% Application callbacks
-export([start/2, stop/1]).
-define(C_ACCEPTORS, 100).
%% ===================================================================
%% Application callbacks
%% ===================================================================
start(_StartType, _StartArgs) ->
Routes = routes(),
Dispatch = cowboy_router:compile(Routes),
Port = port(),
TransOpts = [{port, Port}],
ProtoOpts = [{env, [{dispatch, Dispatch}]}],
{ok, _} = cowboy:start_http(http, ?C_ACCEPTORS, TransOpts, ProtoOpts),
erlblog_sup:start_link().
stop(_State) ->
ok.
%% ===================================================================
%% Internal functions
%% ===================================================================
routes() ->
[
{‘_‘, [
{"/", erlblog_handler, []}
]}
].
port() ->
case os:getenv("PORT") of
false ->
{ok, Port} = application:get_env(http_port),
Port;
Other ->
list_to_integer(Other)
end.
添加请求处理模块
$ cat src/erlblog_handler.erl
-module(erlblog_handler).
-export([init/3]).
-export([handle/2]).
-export([terminate/3]).
init(_Transport, Req, []) ->
{ok, Req, undefined}.
handle(Req, State) ->
{ok, Req2} = cowboy_req:reply(200, [], <<"Hello world!">>, Req),
{ok, Req2, State}.
terminate(_Reason, _Req, _State) ->
ok.
Finally, let’s create an interface module which will be responsible for starting your erlblog application together with all its dependencies.
erlblog模块内容:
$ cat src/erlblog.erl
-module(erlblog).
-export([start/0]).
start() ->
ok = application:start(crypto),
ok = application:start(ranch),
ok = application:start(cowboy),
ok = application:start(erlblog).
使用rebar 获得Cowboy程序以及依赖程序并编译
$ ./rebar get-deps compile
启动程序
$ erl -pa ebin deps/*/ebin -s erlblog
1> application:which_applications().
最后使用浏览器访问测试
http://服务器IP:8080/ 返回hello, world表示能正确使用Cowboy