一：查看你下载的MySQL和mysql-connector-java，如果不对应的话肯定会报错。
对应规则：
mysql-connector-java-5
| Connector/J version | Driver Type | JDBC version | MySQL Server version | Status |
|---|---|---|---|---|
| 5.1 | 4 | 3.0, 4.0, 4.1, 4.2 | 4.1, 5.0, 5.1, 5.5, 5.6, 5.7 | Recommended version |
| 5.0 | 4 | 3.0 | 4.1, 5.0 | Released version |
| 3.1 | 4 | 3.0 | 4.1, 5.0 | Obsolete |
| 3.0 | 4 | 3.0 | , 4.1 | Obsolete |
官方：mysql-connector-java-5
mysql-connector-java-6
| Connector/J version | JDBC version | MySQL Server version | JRE Supported | JDK Required for Compilation | Status |
|---|---|---|---|---|---|
| 6.0 | 4.2 | 5.5, 5.6, 5.7 | 1. | 1. | Developer Mileston |
| 5.1 | 3.0, 4.0, 4.1, 4.2 | 4.1, 5.0, 5.1, 5.5, 5.6*, 5.7* | 1., 1., 1., 1.* | 1. ,1. | Recommended version |
官方：mysql-connector-java-6
二：配置问题
mysql-connector-java 5：
mysql-connector-java 6：
用反会出错