a possible bug of FileBasedSessionManager

[leizhiyuan]

• I have searched the issues of this repository and believe that this is not a duplicate.

Ⅰ. Issue Description

the full file name is not right.

Ⅱ. Describe what happened

   /**
     * Instantiates a new File based session manager.
     *
     * @param name                 the name
     * @param sessionStoreFilePath the session store file path
     * @throws IOException the io exception
     */
    public FileBasedSessionManager(String name, String sessionStoreFilePath) throws IOException {
        super(name);
        transactionStoreManager = new FileTransactionStoreManager(sessionStoreFilePath + name, this);
    }

the full name is not right

Ⅲ. Describe what you expected to happen

store {
  ## store mode: file、db
  mode = "file"

  ## file store
  file {
    dir = "root.data"

this should be dir, not the file name.

Ⅳ. How to reproduce it (as minimally and precisely as possible)

1. xxx
2. xxx
3. xxx

Ⅴ. Anything else we need to know?

Ⅵ. Environment:

• JDK version :
• OS :
• Others: