在Mysql数据库链接测试中报错，信息如下：
org.apache.ibatis.exceptions.PersistenceException:
### Error querying database. Cause: java.sql.SQLException: Error setting driver on UnpooledDataSource. Cause: java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
### The error may exist in org/activiti/db/mapping/entity/Property.xml
### The error may involve org.activiti.engine.impl.persistence.entity.PropertyEntity.selectDbSchemaVersion
### The error occurred while executing a query
### Cause: java.sql.SQLException: Error setting driver on UnpooledDataSource. Cause: java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:23)
at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:107)
at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:98)
at org.apache.ibatis.session.defaults.DefaultSqlSession.selectOne(DefaultSqlSession.java:62)
at org.apache.ibatis.session.defaults.DefaultSqlSession.selectOne(DefaultSqlSession.java:57)
at org.activiti.engine.impl.db.DbSqlSession.getDbVersion(DbSqlSession.java:1011)
at org.activiti.engine.impl.db.DbSqlSession.dbSchemaCheckVersion(DbSqlSession.java:967)
at org.activiti.engine.impl.db.DbSqlSession.performSchemaOperationsProcessEngineBuild(DbSqlSession.java:1470)
at org.activiti.engine.impl.SchemaOperationsProcessEngineBuild.execute(SchemaOperationsProcessEngineBuild.java:25)
at org.activiti.engine.impl.interceptor.CommandInvoker.execute(CommandInvoker.java:24)
at org.activiti.engine.impl.interceptor.CommandContextInterceptor.execute(CommandContextInterceptor.java:57)
at org.activiti.engine.impl.interceptor.LogInterceptor.execute(LogInterceptor.java:31)
at org.activiti.engine.impl.cfg.CommandExecutorImpl.execute(CommandExecutorImpl.java:40)
at org.activiti.engine.impl.ProcessEngineImpl.<init>(ProcessEngineImpl.java:77)
at org.activiti.engine.impl.cfg.ProcessEngineConfigurationImpl.buildProcessEngine(ProcessEngineConfigurationImpl.java:427)
at test.ActivitiAnginerTest.testActivitiEngine(ActivitiAnginerTest.java:30)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:86)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:539)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:761)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:461)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:207)
Caused by: java.sql.SQLException: Error setting driver on UnpooledDataSource. Cause: java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
at org.apache.ibatis.datasource.unpooled.UnpooledDataSource.initializeDriver(UnpooledDataSource.java:211)
at org.apache.ibatis.datasource.unpooled.UnpooledDataSource.doGetConnection(UnpooledDataSource.java:190)
at org.apache.ibatis.datasource.unpooled.UnpooledDataSource.doGetConnection(UnpooledDataSource.java:186)
at org.apache.ibatis.datasource.unpooled.UnpooledDataSource.getConnection(UnpooledDataSource.java:88)
at org.apache.ibatis.datasource.pooled.PooledDataSource.popConnection(PooledDataSource.java:373)
at org.apache.ibatis.datasource.pooled.PooledDataSource.getConnection(PooledDataSource.java:82)
at org.apache.ibatis.transaction.jdbc.JdbcTransaction.openConnection(JdbcTransaction.java:131)
at org.apache.ibatis.transaction.jdbc.JdbcTransaction.getConnection(JdbcTransaction.java:58)
at org.apache.ibatis.executor.BaseExecutor.getConnection(BaseExecutor.java:271)
at org.apache.ibatis.executor.SimpleExecutor.prepareStatement(SimpleExecutor.java:69)
at org.apache.ibatis.executor.SimpleExecutor.doQuery(SimpleExecutor.java:56)
at org.apache.ibatis.executor.BaseExecutor.queryFromDatabase(BaseExecutor.java:259)
at org.apache.ibatis.executor.BaseExecutor.query(BaseExecutor.java:132)
at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:105)
at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:81)
at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:104)
... 37 more
注意：jar包版本过高是还会报另外一个错误，信息如下：
org.apache.ibatis.exceptions.PersistenceException:
### Error querying database. Cause: java.sql.SQLException: The server time zone value '�й���ʱ��' is unrecognized or represents more than one time zone. You must configure either the server or JDBC driver (via the serverTimezone configuration property) to use a more specifc time zone value if you want to utilize time zone support.
### The error may exist in org/activiti/db/mapping/entity/Property.xml
### The error may involve org.activiti.engine.impl.persistence.entity.PropertyEntity.selectDbSchemaVersion
### The error occurred while executing a query
### Cause: java.sql.SQLException: The server time zone value '�й���ʱ��' is unrecognized or represents more than one time zone. You must configure either the server or JDBC driver (via the serverTimezone configuration property) to use a more specifc time zone value if you want to utilize time zone support.
at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:23)
at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:107)
at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:98)
at org.apache.ibatis.session.defaults.DefaultSqlSession.selectOne(DefaultSqlSession.java:62)
at org.apache.ibatis.session.defaults.DefaultSqlSession.selectOne(DefaultSqlSession.java:57)
at org.activiti.engine.impl.db.DbSqlSession.getDbVersion(DbSqlSession.java:1011)
at org.activiti.engine.impl.db.DbSqlSession.dbSchemaCheckVersion(DbSqlSession.java:967)
at org.activiti.engine.impl.db.DbSqlSession.performSchemaOperationsProcessEngineBuild(DbSqlSession.java:1470)
at org.activiti.engine.impl.SchemaOperationsProcessEngineBuild.execute(SchemaOperationsProcessEngineBuild.java:25)
at org.activiti.engine.impl.interceptor.CommandInvoker.execute(CommandInvoker.java:24)
at org.activiti.engine.impl.interceptor.CommandContextInterceptor.execute(CommandContextInterceptor.java:57)
at org.activiti.engine.impl.interceptor.LogInterceptor.execute(LogInterceptor.java:31)
at org.activiti.engine.impl.cfg.CommandExecutorImpl.execute(CommandExecutorImpl.java:40)
at org.activiti.engine.impl.ProcessEngineImpl.<init>(ProcessEngineImpl.java:77)
at org.activiti.engine.impl.cfg.ProcessEngineConfigurationImpl.buildProcessEngine(ProcessEngineConfigurationImpl.java:427)
at test.ActivitiAnginerTest.testActivitiEngine(ActivitiAnginerTest.java:30)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:86)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:539)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:761)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:461)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:207)
Caused by: java.sql.SQLException: The server time zone value '�й���ʱ��' is unrecognized or represents more than one time zone. You must configure either the server or JDBC driver (via the serverTimezone configuration property) to use a more specifc time zone value if you want to utilize time zone support.
at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:569)
at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:537)
at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:527)
at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:512)
at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:480)
at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:498)
at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:494)
at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:69)
at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:1634)
at com.mysql.cj.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:637)
at com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:351)
at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:224)
at java.sql.DriverManager.getConnection(DriverManager.java:664)
at java.sql.DriverManager.getConnection(DriverManager.java:208)
at org.apache.ibatis.datasource.unpooled.UnpooledDataSource.doGetConnection(UnpooledDataSource.java:191)
at org.apache.ibatis.datasource.unpooled.UnpooledDataSource.doGetConnection(UnpooledDataSource.java:186)
at org.apache.ibatis.datasource.unpooled.UnpooledDataSource.getConnection(UnpooledDataSource.java:88)
at org.apache.ibatis.datasource.pooled.PooledDataSource.popConnection(PooledDataSource.java:373)
at org.apache.ibatis.datasource.pooled.PooledDataSource.getConnection(PooledDataSource.java:82)
at org.apache.ibatis.transaction.jdbc.JdbcTransaction.openConnection(JdbcTransaction.java:131)
at org.apache.ibatis.transaction.jdbc.JdbcTransaction.getConnection(JdbcTransaction.java:58)
at org.apache.ibatis.executor.BaseExecutor.getConnection(BaseExecutor.java:271)
at org.apache.ibatis.executor.SimpleExecutor.prepareStatement(SimpleExecutor.java:69)
at org.apache.ibatis.executor.SimpleExecutor.doQuery(SimpleExecutor.java:56)
at org.apache.ibatis.executor.BaseExecutor.queryFromDatabase(BaseExecutor.java:259)
at org.apache.ibatis.executor.BaseExecutor.query(BaseExecutor.java:132)
at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:105)
at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:81)
at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:104)
... 37 more
Caused by: com.mysql.cj.core.exceptions.InvalidConnectionAttributeException: The server time zone value '�й���ʱ��' is unrecognized or represents more than one time zone. You must configure either the server or JDBC driver (via the serverTimezone configuration property) to use a more specifc time zone value if you want to utilize time zone support.
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
at com.mysql.cj.core.exceptions.ExceptionFactory.createException(ExceptionFactory.java:54)
at com.mysql.cj.core.exceptions.ExceptionFactory.createException(ExceptionFactory.java:73)
at com.mysql.cj.jdbc.util.TimeUtil.getCanonicalTimezone(TimeUtil.java:118)
at com.mysql.cj.mysqla.MysqlaSession.configureTimezone(MysqlaSession.java:293)
at com.mysql.cj.jdbc.ConnectionImpl.initializePropsFromServer(ConnectionImpl.java:2424)
at com.mysql.cj.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:1767)
at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:1624)
... 57 more
这个错误是因为mysql连接的依赖包是高版本的情况下：
在配置datasource.url时要加上一些必要的后缀
jdbc:mysql://127.0.0.1:3306/activiti?useUnicode=true&useJDBCCompliantTimezoneShift=true&useLegacyDatetimeCode=false&serverTimezone=UTC