新手问题 Windows 下面 Ruby 错误 Could not load 'active_record/connection_adapters/sqlite3_adapter'.
- Ruby 环境：ruby 2.1.3p242 (2014-09-19 revision 47630) [x64-mingw32]
- Rails 环境：Rails 4.1.6
- Widows 环境：win7 64bit
sqlite3-1.3.9-x64-mingw32.gemspec 文件中已修改为 s.require_paths= ["lib/sqlite3_native"]
相关的 dll 文件也放入 Ruby 的 Bin 文件之中，而且 Gemfile 文件中的 sqlite3 和 Gemfile.lock 中的版本一致，但是访问网页会抛出错误如下：
Could not load 'active_record/connection_adapters/sqlite3_adapter'. Make sure that the adapter in config/database.yml is valid. If you use an adapter other than 'mysql', 'mysql2', 'postgresql' or 'sqlite3' add the necessary adapter gem to the Gemfile.
异常链如下：
activesupport (4.1.6) lib/active_support/dependencies.rb:247:in `require'
activesupport (4.1.6) lib/active_support/dependencies.rb:247:in `block in require'
activesupport (4.1.6) lib/active_support/dependencies.rb:232:in `load_dependency'
activesupport (4.1.6) lib/active_support/dependencies.rb:247:in `require'
activerecord (4.1.6) lib/active_record/connection_adapters/sqlite3_adapter.rb:6:in `<top (required)>'
activesupport (4.1.6) lib/active_support/dependencies.rb:247:in `require'
activesupport (4.1.6) lib/active_support/dependencies.rb:247:in `block in require'
activesupport (4.1.6) lib/active_support/dependencies.rb:232:in `load_dependency'
activesupport (4.1.6) lib/active_support/dependencies.rb:247:in `require'
activerecord (4.1.6) lib/active_record/connection_adapters/connection_specification.rb:188:in `spec'
activerecord (4.1.6) lib/active_record/connection_handling.rb:50:in `establish_connection'
activerecord (4.1.6) lib/active_record/railtie.rb:129:in `block (2 levels) in <class:Railtie>'
activesupport (4.1.6) lib/active_support/lazy_load_hooks.rb:38:in `instance_eval'
activesupport (4.1.6) lib/active_support/lazy_load_hooks.rb:38:in `execute_hook'
activesupport (4.1.6) lib/active_support/lazy_load_hooks.rb:45:in `block in run_load_hooks'
activesupport (4.1.6) lib/active_support/lazy_load_hooks.rb:44:in `each'
activesupport (4.1.6) lib/active_support/lazy_load_hooks.rb:44:in `run_load_hooks'
activerecord (4.1.6) lib/active_record/base.rb:326:in `<module:ActiveRecord>'
activerecord (4.1.6) lib/active_record/base.rb:23:in `<top (required)>'
activerecord (4.1.6) lib/active_record/connection_adapters/abstract/connection_pool.rb:628:in `rescue in call'
activerecord (4.1.6) lib/active_record/connection_adapters/abstract/connection_pool.rb:619:in `call'
activerecord (4.1.6) lib/active_record/migration.rb:380:in `call'
actionpack (4.1.6) lib/action_dispatch/middleware/callbacks.rb:29:in `block in call'
activesupport (4.1.6) lib/active_support/callbacks.rb:82:in `run_callbacks'
actionpack (4.1.6) lib/action_dispatch/middleware/callbacks.rb:27:in `call'
actionpack (4.1.6) lib/action_dispatch/middleware/reloader.rb:73:in `call'
actionpack (4.1.6) lib/action_dispatch/middleware/remote_ip.rb:76:in `call'
actionpack (4.1.6) lib/action_dispatch/middleware/debug_exceptions.rb:17:in `call'
actionpack (4.1.6) lib/action_dispatch/middleware/show_exceptions.rb:30:in `call'
railties (4.1.6) lib/rails/rack/logger.rb:38:in `call_app'
railties (4.1.6) lib/rails/rack/logger.rb:20:in `block in call'
activesupport (4.1.6) lib/active_support/tagged_logging.rb:68:in `block in tagged'
activesupport (4.1.6) lib/active_support/tagged_logging.rb:26:in `tagged'
activesupport (4.1.6) lib/active_support/tagged_logging.rb:68:in `tagged'
railties (4.1.6) lib/rails/rack/logger.rb:20:in `call'
actionpack (4.1.6) lib/action_dispatch/middleware/request_id.rb:21:in `call'
rack (1.5.2) lib/rack/methodoverride.rb:21:in `call'
rack (1.5.2) lib/rack/runtime.rb:17:in `call'
activesupport (4.1.6) lib/active_support/cache/strategy/local_cache_middleware.rb:26:in `call'
rack (1.5.2) lib/rack/lock.rb:17:in `call'
actionpack (4.1.6) lib/action_dispatch/middleware/static.rb:64:in `call'
rack (1.5.2) lib/rack/sendfile.rb:112:in `call'
railties (4.1.6) lib/rails/engine.rb:514:in `call'
railties (4.1.6) lib/rails/application.rb:144:in `call'
rack (1.5.2) lib/rack/lock.rb:17:in `call'
rack (1.5.2) lib/rack/content_length.rb:14:in `call'
rack (1.5.2) lib/rack/handler/webrick.rb:60:in `service'
E:/Tool/Ruby21-x64/lib/ruby/2.1.0/webrick/httpserver.rb:138:in `service'
E:/Tool/Ruby21-x64/lib/ruby/2.1.0/webrick/httpserver.rb:94:in `run'
E:/Tool/Ruby21-x64/lib/ruby/2.1.0/webrick/server.rb:295:in `block in start_thread'
求解惑~~
新来的第一篇就献给你了兄弟： 这个问题我也折腾了几个小时，解决这个问题需要重新编译和安装 gem sqlite3, 要想编译安装本地 gem，需要 Ruby 的 DevKit，请先下载安装： Win32 版本：http://cdn.rubyinstaller.org/archives/devkits/DevKit-mingw64-32-4.7.2-20130224-1151-sfx.exe Win64 版本：http://cdn.rubyinstaller.org/archives/devkits/DevKit-mingw64-64-4.7.2-20130224-1432-sfx.exe
按照文章中说明：https://github.com/oneclick/rubyinstaller/wiki/Development-KitDevKit，安装 1) 执行 DevKit 初始化
>ruby dk.rb init
它会生成一个空的 config.yml 文件，把你的 Ruby 安装路径填进去，如：- D:/Ruby21-x64 2) 执行安装
>ruby dk.rb install
这样就可以了，测试一下：
>gem install json --platform=ruby
>ruby -rubygems -e "require 'json'; puts JSON.load('[42]').inspect"
如果输出 [42] 就 OK 了
接下来重装 gem sqlite3. 先下载所需文件： Win32 版本 DLL：http://www.sqlite.org/snapshot/sqlite-dll-win32-x86-201409200035.zip Win64 版本 DLL：http://www.sqlite.org/snapshot/sqlite-dll-win64-x64-201409200035.zip sqlite 源代码：http://www.sqlite.org/2014/sqlite-autoconf-3080600.tar.gz
解压文件之后，先卸载之前安装的 sqlite3:
>gem uninstall sqlite3
如果有多个的话都给它卸掉，然后编译安装新的 gem：
>gem install sqlite3 --platform=ruby -- --with-sqlite3-include=D:/sqlite3/src --with-sqlite3-lib=D:/sqlite3/bin
其中--with-sqlite3-include 对应 sqlite 源码（sqlite3.h 所在）文件夹，--with-sqlite3-lib 对应 dll 所在文件夹。安装好 gem sqlite3 之后就万事大吉了。
其实 win 下的 ruby 还是装 version 1.9.3 的好，非要装 2.0.0 的话推荐装 32 位的，64 位上次看到说要在注册表添加一个值我一下给忘了。
不能因为某些 gem 无法在 win 下用而断言 ruby 在 win 里面不行。这是写 gem 的人造成的，而不是 ruby 造成的
