java.sql.SQLException: Unknown system variable 'query_cache_size'
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:964) ~[mysql-connector-java-5.1.41.jar:5.1.41]
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3973) ~[mysql-connector-java-5.1.41.jar:5.1.41]
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3909) ~[mysql-connector-java-5.1.41.jar:5.1.41]
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2527) ~[mysql-connector-java-5.1.41.jar:5.1.41]
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2680) ~[mysql-connector-java-5.1.41.jar:5.1.41]
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2497) ~[mysql-connector-java-5.1.41.jar:5.1.41]
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2455) ~[mysql-connector-java-5.1.41.jar:5.1.41]
at com.mysql.jdbc.StatementImpl.executeQuery(StatementImpl.java:1369) ~[mysql-connector-java-5.1.41.jar:5.1.41]
at com.mysql.jdbc.ConnectionImpl.loadServerVariables(ConnectionImpl.java:3777) ~[mysql-connector-java-5.1.41.jar:5.1.41]
at com.mysql.jdbc.ConnectionImpl.initializePropsFromServer(ConnectionImpl.java:3240) ~[mysql-connector-java-5.1.41.jar:5.1.41]
at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2249) ~[mysql-connector-java-5.1.41.jar:5.1.41]
at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2035) ~[mysql-connector-java-5.1.41.jar:5.1.41]
at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:790) ~[mysql-connector-java-5.1.41.jar:5.1.41]
at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47) ~[mysql-connector-java-5.1.41.jar:5.1.41]
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[na:1.8.0_181]
at
原因是mysql-connector-java的版本过低，需要升级版本到8.0.11 ，如下所示：
.
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.11</version>
</dependency>
版本升级之后，运行正常。