Connections could not be acquired from the underlying database!

Connections could not be acquired from the underlying database!

 

以上問題可能有一下緣由形成：

1，驅動配置有誤：driver=com.mysql.jdbc.Driver
2，數據庫鏈接地址有誤：url=jdbc:mysql://localhost:3306/test?3useUnicode=true&characterEncoding=utf8
3，密碼或賬號有誤：username=root
      password=root

4，數據庫未啓動或無權訪問

5，項目未引入對應的驅動jar包mysql-connector-java-5.1.6-bin.jar

6,mysql root沒有遠程訪問的權限，須要增長權限，增長權限的步驟以下：
進入mysql數據庫：
grant all privileges on *.* to 'root'@'%' identified by 'root' with grant option;
flush privileges;