Laravel 4.2 Composer安装错误:；无法扫描类”；

我想通过Composer在我的新Laravel 4.2安装上安装一些软件包。然而，我遇到了一个例外。

这是我的Composer文件：

{
    "name": "laravel/laravel",
    "description": "The Laravel Framework.",
    "keywords": ["framework", "laravel"],
    "license": "MIT",
    "license": "MIT",   
    "require": {
        "laravel/framework": "4.2.*",
        "zizaco/confide": "~4.0@dev",
        "zizaco/entrust": "1.2.*@dev",
        "barryvdh/laravel-ide-helper": "1.*",
        "fzaninotto/faker": "1.3.*@dev",
        "bllim/datatables": "~1.3",
        "barryvdh/laravel-debugbar": "~1.7"
    },
    "require-dev": {
        "way/generators": "~2.6",
        "barryvdh/laravel-ide-helper": "~1.11"
    },
    "autoload": {
        "classmap": [
            "app/commands",
            "app/controllers",
            "app/models",
            "app/database/migrations",
            "app/database/seeds",
            "app/tests/TestCase.php",
            "app/controllers/admin",
            "app/controllers/user"
        ]
    },
    "scripts": {
        "post-install-cmd": [
            "php artisan clear-compiled",
            "php artisan optimize"
        ],
        "post-update-cmd": [
            "php artisan clear-compiled",
            "php artisan optimize"
        ],
        "post-update-cmd":[
            "php artisan ide-helper:generate"
        ],
        "post-create-project-cmd": [
            "php artisan key:generate"
        ]
    },
    "config": {
        "preferred-install": "dist"
    },
    "minimum-stability": "stable"
}

当运行composer install时，我得到：

$ composer install
Loading composer repositories with package information
Installing dependencies (including require-dev) from lock file
Warning: The lock file is not up to date with the latest changes in composer.jso
n. You may be getting outdated dependencies. Run update to update them.
Nothing to install or update
Generating autoload files

  [RuntimeException]
  Could not scan for classes inside "app/controllers/admin" which does not ap
  pear to be a file nor a folder

install [--prefer-source] [--prefer-dist] [--dry-run] [--dev] [--no-dev] [--no-p
lugins] [--no-custom-installers] [--no-scripts] [--no-progress] [-v|vv|vvv|--ver
bose] [-o|--optimize-autoloader] [packages1] ... [packagesN]

这基本上是一个全新的Laravel装置。为什么我会得到错误：

Could not scan for classes inside "app/controllers/admin" which does not appear to be a file nor a folder

更新

使用composer update:

$ composer update
Loading composer repositories with package information
Updating dependencies (including require-dev)
  - Removing mockery/mockery (0.9.2)
  - Removing phpunit/phpunit (4.3.4)
  - Removing phpunit/php-code-coverage (2.0.11)
  - Removing phpunit/php-token-stream (1.3.0)
  - Removing phpunit/php-file-iterator (1.3.4)
  - Removing phpunit/php-timer (1.0.5)
  - Removing phpunit/phpunit-mock-objects (2.3.0)
  - Removing phpunit/php-text-template (1.2.0)
  - Removing doctrine/instantiator (1.0.4)
  - Removing symfony/yaml (v2.5.6)
  - Removing sebastian/comparator (1.0.1)
  - Removing sebastian/diff (1.2.0)
  - Removing sebastian/environment (1.2.0)
  - Removing sebastian/exporter (1.0.2)
  - Removing sebastian/version (1.0.3)
  - Removing summerstreet/woodling (v0.1.6)
Writing lock file
Generating autoload files

  [RuntimeException]
  Could not scan for classes inside "app/controllers/admin" which does not ap
  pear to be a file nor a folder

update [--prefer-source] [--prefer-dist] [--dry-run] [--dev] [--no-dev] [--lock]
 [--no-plugins] [--no-custom-installers] [--no-scripts] [--no-progress] [--with-
dependencies] [-v|vv|vvv|--verbose] [-o|--optimize-autoloader] [packages1] ... [
packagesN]