Cause: java.sql.SQLException: Error setting driver on UnpooledDataSource.的解决方法

• 错误展示
• 原因所在
• 解决方法
• • 在终端查看：MySQL版本
  • 将mysql-connector-java的版本修改至等于或高于MySQL版本

"C:Program FilesJavajdk1.8.0_131binjava.exe" -Dmaven.multiModuleProjectDirectory=C:UsersHPDesktopprogramjavarequest-demo "-Dmaven.home=C:Program FilesJetBrainsIntelliJ IDEA 2020.2.1pluginsmavenlibmaven3" "-Dclassworlds.conf=C:Program FilesJetBrainsIntelliJ IDEA 2020.2.1pluginsmavenlibmaven3binm2.conf" "-Dmaven.ext.class.path=C:Program FilesJetBrainsIntelliJ IDEA 2020.2.1pluginsmavenlibmaven-event-listener.jar" "-javaagent:C:Program FilesJetBrainsIntelliJ IDEA 2020.2.1libidea_rt.jar=10923:C:Program FilesJetBrainsIntelliJ IDEA 2020.2.1bin" -Dfile.encoding=UTF-8 -classpath "C:Program FilesJetBrainsIntelliJ IDEA 2020.2.1pluginsmavenlibmaven3bootplexus-classworlds-2.6.0.jar;C:Program FilesJetBrainsIntelliJ IDEA 2020.2.1pluginsmavenlibmaven3bootplexus-classworlds.license" org.codehaus.classworlds.Launcher -Didea.version=2020.2.1 -s C:environmentapache-maven-3.6.3confsettings.xml -Dmaven.repo.local=C:environmentapache-maven-3.6.3maven-repo tomcat7:run
[INFO] Scanning for projects...
[INFO] 
[INFO] ----------------------< org.example:request-demo >----------------------
[INFO] Building request-demo 1.0-SNAPSHOT
[INFO] --------------------------------[ war ]---------------------------------
[INFO] 
[INFO] >>> tomcat7-maven-plugin:2.2:run (default-cli) > process-classes @ request-demo >>>
[INFO] 
[INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ request-demo ---
[WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent!
[INFO] Copying 2 resources
[INFO] 
[INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ request-demo ---
[INFO] Nothing to compile - all classes are up to date
[INFO] 
[INFO] <<< tomcat7-maven-plugin:2.2:run (default-cli) < process-classes @ request-demo <<<
[INFO] 
[INFO] 
[INFO] --- tomcat7-maven-plugin:2.2:run (default-cli) @ request-demo ---
[INFO] Running war on http://localhost:8080/request-demo
[INFO] Using existing Tomcat server configuration at C:UsersHPDesktopprogramjavarequest-demotargettomcat
[INFO] create webapp with contextPath: /request-demo
七月 12, 2022 7:08:32 下午 org.apache.coyote.AbstractProtocol init
信息: Initializing ProtocolHandler ["http-bio-8080"]
七月 12, 2022 7:08:32 下午 org.apache.catalina.core.StandardService startInternal
信息: Starting service Tomcat
七月 12, 2022 7:08:32 下午 org.apache.catalina.core.StandardEngine startInternal
信息: Starting Servlet Engine: Apache Tomcat/7.0.47
七月 12, 2022 7:08:33 下午 org.apache.coyote.AbstractProtocol start
信息: Starting ProtocolHandler ["http-bio-8080"]
七月 12, 2022 7:08:56 下午 org.apache.catalina.core.StandardWrapperValve invoke
严重: Servlet.service() for servlet [com.itheima.web.LoginServlet] in context with path [/request-demo] threw exception
org.apache.ibatis.exceptions.PersistenceException: 
### Error querying database.  Cause: java.sql.SQLException: Error setting driver on UnpooledDataSource. Cause: java.lang.ClassNotFoundException: Cannot find class: com.mysql.cj.jdbc.Driver
### The error may exist in com/itheima/mapper/UserMapper.java (best guess)
### The error may involve com.itheima.mapper.UserMapper.select
### The error occurred while executing a query
### Cause: java.sql.SQLException: Error setting driver on UnpooledDataSource. Cause: java.lang.ClassNotFoundException: Cannot find class: com.mysql.cj.jdbc.Driver
	at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:30)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:149)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:140)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectOne(DefaultSqlSession.java:76)
	at org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java:87)
	at org.apache.ibatis.binding.MapperProxy$PlainMethodInvoker.invoke(MapperProxy.java:152)
	at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:85)
	at com.sun.proxy.$Proxy31.select(Unknown Source)
	at com.itheima.web.LoginServlet.doGet(LoginServlet.java:38)
	at com.itheima.web.LoginServlet.doPost(LoginServlet.java:58)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:647)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
	at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:953)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
	at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1041)
	at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:603)
	at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:312)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
	at java.lang.Thread.run(Thread.java:748)
Caused by: java.sql.SQLException: Error setting driver on UnpooledDataSource. Cause: java.lang.ClassNotFoundException: Cannot find class: com.mysql.cj.jdbc.Driver
	at org.apache.ibatis.datasource.unpooled.UnpooledDataSource.initializeDriver(UnpooledDataSource.java:244)
	at org.apache.ibatis.datasource.unpooled.UnpooledDataSource.doGetConnection(UnpooledDataSource.java:223)
	at org.apache.ibatis.datasource.unpooled.UnpooledDataSource.doGetConnection(UnpooledDataSource.java:219)
	at org.apache.ibatis.datasource.unpooled.UnpooledDataSource.getConnection(UnpooledDataSource.java:95)
	at org.apache.ibatis.datasource.pooled.PooledDataSource.popConnection(PooledDataSource.java:432)
	at org.apache.ibatis.datasource.pooled.PooledDataSource.getConnection(PooledDataSource.java:89)
	at org.apache.ibatis.transaction.jdbc.JdbcTransaction.openConnection(JdbcTransaction.java:139)
	at org.apache.ibatis.transaction.jdbc.JdbcTransaction.getConnection(JdbcTransaction.java:61)
	at org.apache.ibatis.executor.BaseExecutor.getConnection(BaseExecutor.java:337)
	at org.apache.ibatis.executor.SimpleExecutor.prepareStatement(SimpleExecutor.java:86)
	at org.apache.ibatis.executor.SimpleExecutor.doQuery(SimpleExecutor.java:62)
	at org.apache.ibatis.executor.BaseExecutor.queryFromDatabase(BaseExecutor.java:325)
	at org.apache.ibatis.executor.BaseExecutor.query(BaseExecutor.java:156)
	at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:109)
	at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:89)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:147)
	... 29 more

• mysql-connector-java与MySQL版本不兼容
  

mysql --version

            mysql
            mysql-connector-java
            8.0.28