Erlang boss_db hello world？

Question

最近我尝试为 Erlang 安装并运行 boss_db ORM 的演示。

这是我所做的：

• 克隆存储库
• cd boss_db/
• rebar get-deps

• 将一个简单的 mydb.erl 文件放入src/：

  -module(mydb).
  
  -compile(export_all).
  
  start() ->
  

  DBOptions = [{适配器，pgsql}， {db_host, "localhost"}, {db_port, 5432}, {db_username, "postgres"}, {db_password, "mypass"},
  {cache_enable, false}, {cache_exp_time, 0}],

  boss_db:start(DBOptions).

• rebar compile

• cd ebin/
• 运行erl
• mydb:start()

这是我得到的：

** exception exit: shutdown

我在这里做错了什么？它应该如何运行？

附：我也尝试运行 application:start(boss_db)，但结果是一样的。

附言我已经阅读了documentation 两次，但我仍然不知道如何运行整个内容。

Answer 1

您没有将依赖项添加到代码路径。这就是为什么在找不到它们时会引发异常的原因。不要 cd 进入 ebin 和 erl。而是运行

erl -pa ebin -pa deps/*/ebin

从当前目录。

顺便说一句，这不是做这类事情的好方法。而是使用 rebar 创建一个新的空应用程序。在 rebar.config 中将 boss_db 作为依赖项添加到您的应用程序。将自己的源文件放在 src 下。然后

rebar get-deps compile
erl -pa ebin -pa deps/*/ebin

Answer 2

git clone git://github.com/evanmiller/boss_db.git
cd boss_db/
rebar get-deps
emacs src/mydb.erl
rebar compile
erl -pa ./ebin ./deps/*/ebin

这些步骤对我有用。 code:is_loaded() 在您运行 erl 后将无法正常工作。只有在调用模块时，才会加载代码。

我确实遇到了应用程序关闭，但这是因为代码正在尝试连接到 Postgres DB 并且无法连接到它。

Erlang R15B02 (erts-5.9.2) [source] [smp:8:8] [async-threads:0] [hipe] [kernel-poll:false]

Eshell V5.9.2  (abort with ^G)
1> mydb:start().
** exception exit: shutdown
=ERROR REPORT==== 9-Oct-2012::12:13:07 ===
** Generic server <0.35.0> terminating 
** Last message in was {'EXIT',<0.34.0>,
                        {{badmatch,
                          {error,
                           {{badmatch,
                             {error,
                              {{badmatch,{error,econnrefused}},
                               [{pgsql_sock,init,1,
                                 [{file,"src/pgsql_sock.erl"},{line,51}]},
                                {gen_server,init_it,6,
                                 [{file,"gen_server.erl"},{line,304}]},
                                {proc_lib,init_p_do_apply,3,
                                 [{file,"proc_lib.erl"},{line,227}]}]}}},
                            [{boss_db_controller,init,1,
                              [{file,"src/boss_db_controller.erl"},{line,31}]},
                             {gen_server,init_it,6,
                              [{file,"gen_server.erl"},{line,304}]},
                             {proc_lib,init_p_do_apply,3,
                              [{file,"proc_lib.erl"},{line,227}]}]}}},
                         [{poolboy,new_worker,2,
                           [{file,"src/poolboy.erl"},{line,348}]},
                          {poolboy,prepopulate,4,
                           [{file,"src/poolboy.erl"},{line,370}]},
                          {poolboy,init,2,
                           [{file,"src/poolboy.erl"},{line,74}]},
                          {gen_fsm,init_it,6,
                           [{file,"gen_fsm.erl"},{line,361}]},
                          {proc_lib,init_p_do_apply,3,
                           [{file,"proc_lib.erl"},{line,227}]}]}}
** When Server state == {state,
                            {<0.35.0>,poolboy_sup},
                            simple_one_for_one,
                            [{child,undefined,boss_db_controller,
                                 {boss_db_controller,start_link,
                                     [[{size,5},
                                       {max_overflow,10},
                                       {adapter,pgsql},
                                       {db_host,"localhost"},
                                       {db_port,5432},
                                       {db_username,"postgres"},
                                       {db_password,"mypass"},
                                       {cache_enable,false},
                                       {cache_exp_time,0}]]},
                                 temporary,brutal_kill,worker,
                                 [boss_db_controller]}],
                            {set,0,16,16,8,80,48,
                                {[],[],[],[],[],[],[],[],[],[],[],[],[],[],[],
                                 []},
                                {{[],[],[],[],[],[],[],[],[],[],[],[],[],[],
                                  [],[]}}},
                            0,1,[],poolboy_sup,
                            {boss_db_controller,
                                [{size,5},
                                 {max_overflow,10},
                                 {adapter,pgsql},
                                 {db_host,"localhost"},
                                 {db_port,5432},
                                 {db_username,"postgres"},
                                 {db_password,"mypass"},
                                 {cache_enable,false},
                                 {cache_exp_time,0}]}}
** Reason for termination == 
** {{badmatch,
        {error,
            {{badmatch,
                 {error,
                     {{badmatch,{error,econnrefused}},
                      [{pgsql_sock,init,1,
                           [{file,"src/pgsql_sock.erl"},{line,51}]},
                       {gen_server,init_it,6,
                           [{file,"gen_server.erl"},{line,304}]},
                       {proc_lib,init_p_do_apply,3,
                           [{file,"proc_lib.erl"},{line,227}]}]}}},
             [{boss_db_controller,init,1,
                  [{file,"src/boss_db_controller.erl"},{line,31}]},
              {gen_server,init_it,6,[{file,"gen_server.erl"},{line,304}]},
              {proc_lib,init_p_do_apply,3,
                  [{file,"proc_lib.erl"},{line,227}]}]}}},
    [{poolboy,new_worker,2,[{file,"src/poolboy.erl"},{line,348}]},
     {poolboy,prepopulate,4,[{file,"src/poolboy.erl"},{line,370}]},
     {poolboy,init,2,[{file,"src/poolboy.erl"},{line,74}]},
     {gen_fsm,init_it,6,[{file,"gen_fsm.erl"},{line,361}]},
     {proc_lib,init_p_do_apply,3,[{file,"proc_lib.erl"},{line,227}]}]}