public function getContent()
    {
        if ($this->_content === null) {
            if (!$this->canRead()) {
                throw new Exception("Unable to read config file {$this->file}.");
            }
            
            $buffer = $this->getFileContent($this->file);
            $this->_content = $this->jsonDecode($buffer);
        }
        
        return $this->_content;
    }