报错信息：java.sql.SQLException: Unknown system variable 'tx_isolation' at com.mysql.jdbc.SQLError.createSQLException(SQLError. ~[mysql-connector-java-5.1.43.jar:5.1.43] at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO. ~[mysql-connector-java-5.1.43.jar:5.1.43] at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO. ~[mysql-connector-java-5.1.43.jar:5.1.43] at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO. ~[mysql-connector-java-5.1.43.jar:5.1.43] at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO. ~[mysql-connector-java-5.1.43.jar:5.1.43] at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl. ~[mysql-connector-java-5.1.43.jar:5.1.43] at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl. ~[mysql-connector-java-5.1.43.jar:5.1.43] at com.mysql.jdbc.StatementImpl.executeQuery(StatementImpl. ~[mysql-connector-java-5.1.43.jar:5.1.43] at com.mysql.jdbc.ConnectionImpl.loadServerVariables(ConnectionImpl. ~[mysql-connector-java-5.1.43.jar:5.1.43] at com.mysql.jdbc.ConnectionImpl.initializePropsFromServer(ConnectionImpl. ~[mysql-connector-java-5.1.43.jar:5.1.43] at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl. ~[mysql-connector-java-5.1.43.jar:5.1.43] at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl. ~[mysql-connector-java-5.1.43.jar:5.1.43] at com.mysql.jdbc.ConnectionImpl.(ConnectionImpl. ~[mysql-connector-java-5.1.43.jar:5.1.43] at com.mysql.jdbc.JDBC4Connection.(JDBC4Connection. ~[mysql-connector-java-5.1.43.jar:5.1.43] at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[na:1.8.0_171] at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl. ~[na:1.8.0_171] at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl. ~[na:1.8.0_171] at ~[na:1.8.0_171] at com.mysql.jdbc.Util.handleNewInstance(Util. ~[mysql-connector-java-5.1.43.jar:5.1.43] at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl. ~[mysql-connector-java-5.1.43.jar:5.1.43] at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver. ~[mysql-connector-java-5.1.43.jar:5.1.43] at org.apache.tomcat.jdbc.pool.PooledConnection.connectUsingDriver(PooledConnection. ~[tomcat-jdbc-8.5.16.jar:na] at org.apache.tomcat.jdbc.pool.PooledConnection.connect(PooledConnection. ~[tomcat-jdbc-8.5.16.jar:na] at org.apache.tomcat.jdbc.pool.ConnectionPool.createConnection(ConnectionPool. [tomcat-jdbc-8.5.16.jar:na] at org.apache.tomcat.jdbc.pool.ConnectionPool.borrowConnection(ConnectionPool. [tomcat-jdbc-8.5.16.jar:na] at org.apache.tomcat.jdbc.pool.ConnectionPool.init(ConnectionPool. [tomcat-jdbc-8.5.16.jar:na] at org.apache.tomcat.jdbc.pool.ConnectionPool.(ConnectionPool. [tomcat-jdbc-8.5.16.jar:na] at org.apache.tomcat.jdbc.pool.DataSourceProxy.pCreatePool(DataSourceProxy. [tomcat-jdbc-8.5.16.jar:na] at org.apache.tomcat.jdbc.pool.DataSourceProxy.createPool(DataSourceProxy. [tomcat-jdbc-8.5.16.jar:na] at org.apache.tomcat.jdbc.pool.DataSourceProxy.getConnection(DataSourceProxy. [tomcat-jdbc-8.5.16.jar:na] at org.springframework.jdbc.datasource.DataSourceUtils.doGetConnection(DataSourceUtils. [spring-jdbc-4.3.10.RELEASE.jar:4.3.10.RELEASE] at org.springframework.jdbc.datasource.DataSourceUtils.getConnection(DataSourceUtils. [spring-jdbc-4.3.10.RELEASE.jar:4.3.10.RELEASE] at org.springframework.jdbc.support.JdbcUtils.extractDatabaseMetaData(JdbcUtils. [spring-jdbc-4.3.10.RELEASE.jar:4.3.10.RELEASE] at org.springframework.jdbc.support.JdbcUtils.extractDatabaseMetaData(JdbcUtils. [spring-jdbc-4.3.10.RELEASE.jar:4.3.10.RELEASE] at org.springframework.boot.autoconfigure.orm.jpa.DatabaseLookup.getDatabase(DatabaseLookup. [spring-boot-autoconfigure-1.5.6.RELEASE.jar:1.5.6.RELEASE] at org.springframework.boot.autoconfigure.orm.jpa.JpaProperties.determineDatabase(JpaProperties. [spring-boot-autoconfigure-1.5.6.RELEASE.jar:1.5.6.RELEASE] at org.springframework.boot.autoconfigure.orm.jpa.JpaBaseConfiguration.jpaVendorAdapter(JpaBaseConfiguration. [spring-boot-autoconfigure-1.5.6.RELEASE.jar:1.5.6.RELEASE] at org.springframework.boot.autoconfigure.orm.jpa.HibernateJpaAutoConfiguration

解决办法：在pom.xml文件中将MySQL Connector / J版本升级为8：

            mysql

            mysql-connector-java

             8.0.12

注释：8.0.11时安装的mysql的版本号