Rails 4.2.1启动WEBrick（mysql/windows）时出现问题

我刚开始使用Rails，正在学习RubyonRails基本培训课程，在尝试启动WEBrick时遇到了一些问题。假设这与我安装的mysql有关，但不确定

我确保我在正确的目录中：C\sites\simple\u cms 在运行“rails”之前，我运行了“bundle安装” 我按照以下指南安装了gem，从第二个到最后一个条目： 我已经安装了ruby 2.2.1p85、rails 4.2.1和这个rubygem:mysql2-0.3.18-x64-mingw32

非常感谢你们的帮助：

堆栈跟踪：

    C:\Sites\simple_cms>rails s
    C:/Ruby22-x64/lib/ruby/gems/2.2.0/gems/mysql2-0.3.18-x64-mingw32/lib/mysql2/mysql2.rb:2:in `require': cannot load such file -- mysql2/2.2/mysql2 (LoadError)
    from C:/Ruby22-x64/lib/ruby/gems/2.2.0/gems/mysql2-0.3.18-x64-mingw32/lib/mysql2/mysql2.rb:2:in `<top (required)>'
    from C:/Ruby22-x64/lib/ruby/gems/2.2.0/gems/mysql2-0.3.18-x64-mingw32/lib/mysql2.rb:31:in `require'
    from C:/Ruby22-x64/lib/ruby/gems/2.2.0/gems/mysql2-0.3.18-x64-mingw32/lib/mysql2.rb:31:in `<top (required)>'
    from C:/Ruby22-x64/lib/ruby/gems/2.2.0/gems/bundler-1.9.2/lib/bundler/runtime.rb:76:in `require'
    from C:/Ruby22-x64/lib/ruby/gems/2.2.0/gems/bundler-1.9.2/lib/bundler/runtime.rb:76:in `block (2 levels) in require'
    from C:/Ruby22-x64/lib/ruby/gems/2.2.0/gems/bundler-1.9.2/lib/bundler/runtime.rb:72:in `each'
    from C:/Ruby22-x64/lib/ruby/gems/2.2.0/gems/bundler-1.9.2/lib/bundler/runtime.rb:72:in `block in require'
    from C:/Ruby22-x64/lib/ruby/gems/2.2.0/gems/bundler-1.9.2/lib/bundler/runtime.rb:61:in `each'
    from C:/Ruby22-x64/lib/ruby/gems/2.2.0/gems/bundler-1.9.2/lib/bundler/runtime.rb:61:in `require'
    from C:/Ruby22-x64/lib/ruby/gems/2.2.0/gems/bundler-1.9.2/lib/bundler.rb:134:in `require'
    from C:/Sites/simple_cms/config/application.rb:7:in `<top (required)>'
    from C:/Ruby22-x64/lib/ruby/gems/2.2.0/gems/railties-4.2.1/lib/rails/commands/commands_tasks.rb:78:in `require'
    from C:/Ruby22-x64/lib/ruby/gems/2.2.0/gems/railties-4.2.1/lib/rails/commands/commands_tasks.rb:78:in `block in server'
    from C:/Ruby22-x64/lib/ruby/gems/2.2.0/gems/railties-4.2.1/lib/rails/commands/commands_tasks.rb:75:in `tap'
    from C:/Ruby22-x64/lib/ruby/gems/2.2.0/gems/railties-4.2.1/lib/rails/commands/commands_tasks.rb:75:in `server'
    from C:/Ruby22-x64/lib/ruby/gems/2.2.0/gems/railties-4.2.1/lib/rails/commands/commands_tasks.rb:39:in `run_command!'
    from C:/Ruby22-x64/lib/ruby/gems/2.2.0/gems/railties-4.2.1/lib/rails/commands.rb:17:in `<top (required)>'
    from bin/rails:4:in `require'
    from bin/rails:4:in `<main>'

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我已经通过将mysql版本降级到0.3.20解决了这个错误