数据库相关

2025-09-18

今天想写一个死锁demo，刚开始测试的时候，在同一个service里2个方法加了@Transactional。第一次测试的时候

发现它们是先后进的，就是串行的。我开始以为是因为加@Transactional，导致原来的多线程变同步执行。后来问了AI，AI说不是的。

后来才知道

 我的默认线程池之前都是填的1，只有一个连数据库的线程，所以多线程最后变成了串行执行。

后来改成10就没出现了。

自己写的死锁，系统会被 发现并报错：

2025-09-18T12:10:02.921+08:00 ERROR 19032 --- [nio-8080-exec-1] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed: org.springframework.dao.DeadlockLoserDataAccessException: 
### Error updating database.  Cause: com.mysql.cj.jdbc.exceptions.MySQLTransactionRollbackException: Deadlock found when trying to get lock; try restarting transaction
### The error may exist in org/example/mapper/TestMapper.java (best guess)
### The error may involve org.example.mapper.TestMapper.updateById-Inline
### The error occurred while setting parameters
### SQL: UPDATE tb_test  SET name=?  WHERE id=?
### Cause: com.mysql.cj.jdbc.exceptions.MySQLTransactionRollbackException: Deadlock found when trying to get lock; try restarting transaction
; Deadlock found when trying to get lock; try restarting transaction] with root cause

com.mysql.cj.jdbc.exceptions.MySQLTransactionRollbackException: Deadlock found when trying to get lock; try restarting transaction
    at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:123) ~[mysql-connector-j-8.0.31.jar:8.0.31]
    at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:122) ~[mysql-connector-j-8.0.31.jar:8.0.31]
    at com.mysql.cj.jdbc.ClientPreparedStatement.executeInternal(ClientPreparedStatement.java:916) ~[mysql-connector-j-8.0.31.jar:8.0.31]
    at com.mysql.cj.jdbc.ClientPreparedStatement.execute(ClientPreparedStatement.java:354) ~[mysql-connector-j-8.0.31.jar:8.0.31]
    at com.zaxxer.hikari.pool.ProxyPreparedStatement.execute(ProxyPreparedStatement.java:44) ~[HikariCP-5.0.1.jar:na]
    at com.zaxxer.hikari.pool.HikariProxyPreparedStatement.execute(HikariProxyPreparedStatement.java) ~[HikariCP-5.0.1.jar:na]
    at org.apache.ibatis.executor.statement.PreparedStatementHandler.update(PreparedStatementHandler.java:48) ~[mybatis-3.5.19.jar:3.5.19]
    at org.apache.ibatis.executor.statement.RoutingStatementHandler.update(RoutingStatementHandler.java:75) ~[mybatis-3.5.19.jar:3.5.19]
    at org.apache.ibatis.executor.SimpleExecutor.doUpdate(SimpleExecutor.java:50) ~[mybatis-3.5.19.jar:3.5.19]
    at org.apache.ibatis.executor.BaseExecutor.update(BaseExecutor.java:117) ~[mybatis-3.5.19.jar:3.5.19]
    at org.apache.ibatis.executor.CachingExecutor.update(CachingExecutor.java:76) ~[mybatis-3.5.19.jar:3.5.19]
    at org.apache.ibatis.session.defaults.DefaultSqlSession.update(DefaultSqlSession.java:197) ~[mybatis-3.5.19.jar:3.5.19]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77) ~[na:na]
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
    at java.base/java.lang.reflect.Method.invoke(Method.java:568) ~[na:na]
    at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:425) ~[mybatis-spring-2.1.2.jar:2.1.2]
    at jdk.proxy2/jdk.proxy2.$Proxy69.update(Unknown Source) ~[na:na]
    at org.mybatis.spring.SqlSessionTemplate.update(SqlSessionTemplate.java:288) ~[mybatis-spring-2.1.2.jar:2.1.2]
    at com.baomidou.mybatisplus.core.override.MybatisMapperMethod.execute(MybatisMapperMethod.java:64) ~[mybatis-plus-core-3.5.14.jar:3.5.14]
    at com.baomidou.mybatisplus.core.override.MybatisMapperProxy$PlainMethodInvoker.invoke(MybatisMapperProxy.java:156) ~[mybatis-plus-core-3.5.14.jar:3.5.14]
    at com.baomidou.mybatisplus.core.override.MybatisMapperProxy.invoke(MybatisMapperProxy.java:93) ~[mybatis-plus-core-3.5.14.jar:3.5.14]
    at jdk.proxy2/jdk.proxy2.$Proxy74.updateById(Unknown Source) ~[na:na]
    at org.example.TestService.test(TestService.java:37) ~[classes/:na]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77) ~[na:na]
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
    at java.base/java.lang.reflect.Method.invoke(Method.java:568) ~[na:na]
    at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:343) ~[spring-aop-6.0.11.jar:6.0.11]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:196) ~[spring-aop-6.0.11.jar:6.0.11]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163) ~[spring-aop-6.0.11.jar:6.0.11]
    at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:756) ~[spring-aop-6.0.11.jar:6.0.11]
    at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:123) ~[spring-tx-6.0.11.jar:6.0.11]
    at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:391) ~[spring-tx-6.0.11.jar:6.0.11]
    at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:119) ~[spring-tx-6.0.11.jar:6.0.11]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:184) ~[spring-aop-6.0.11.jar:6.0.11]
    at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:756) ~[spring-aop-6.0.11.jar:6.0.11]
    at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:708) ~[spring-aop-6.0.11.jar:6.0.11]
    at org.example.TestService$$SpringCGLIB$$0.test(<generated>) ~[classes/:na]
    at org.example.TestController.log(TestController.java:40) ~[classes/:na]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77) ~[na:na]
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
    at java.base/java.lang.reflect.Method.invoke(Method.java:568) ~[na:na]
    at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:205) ~[spring-web-6.0.11.jar:6.0.11]
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:150) ~[spring-web-6.0.11.jar:6.0.11]
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:118) ~[spring-webmvc-6.0.11.jar:6.0.11]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:884) ~[spring-webmvc-6.0.11.jar:6.0.11]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:797) ~[spring-webmvc-6.0.11.jar:6.0.11]
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-6.0.11.jar:6.0.11]
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1081) ~[spring-webmvc-6.0.11.jar:6.0.11]
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:974) ~[spring-webmvc-6.0.11.jar:6.0.11]
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1011) ~[spring-webmvc-6.0.11.jar:6.0.11]
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:903) ~[spring-webmvc-6.0.11.jar:6.0.11]
    at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:564) ~[tomcat-embed-core-10.1.11.jar:6.0]
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:885) ~[spring-webmvc-6.0.11.jar:6.0.11]
    at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:658) ~[tomcat-embed-core-10.1.11.jar:6.0]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:205) ~[tomcat-embed-core-10.1.11.jar:10.1.11]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149) ~[tomcat-embed-core-10.1.11.jar:10.1.11]
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51) ~[tomcat-embed-websocket-10.1.11.jar:10.1.11]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:174) ~[tomcat-embed-core-10.1.11.jar:10.1.11]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149) ~[tomcat-embed-core-10.1.11.jar:10.1.11]
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-6.0.11.jar:6.0.11]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116) ~[spring-web-6.0.11.jar:6.0.11]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:174) ~[tomcat-embed-core-10.1.11.jar:10.1.11]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149) ~[tomcat-embed-core-10.1.11.jar:10.1.11]
    at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) ~[spring-web-6.0.11.jar:6.0.11]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116) ~[spring-web-6.0.11.jar:6.0.11]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:174) ~[tomcat-embed-core-10.1.11.jar:10.1.11]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149) ~[tomcat-embed-core-10.1.11.jar:10.1.11]
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[spring-web-6.0.11.jar:6.0.11]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116) ~[spring-web-6.0.11.jar:6.0.11]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:174) ~[tomcat-embed-core-10.1.11.jar:10.1.11]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149) ~[tomcat-embed-core-10.1.11.jar:10.1.11]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:166) ~[tomcat-embed-core-10.1.11.jar:10.1.11]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:90) ~[tomcat-embed-core-10.1.11.jar:10.1.11]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:482) ~[tomcat-embed-core-10.1.11.jar:10.1.11]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:115) ~[tomcat-embed-core-10.1.11.jar:10.1.11]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:93) ~[tomcat-embed-core-10.1.11.jar:10.1.11]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) ~[tomcat-embed-core-10.1.11.jar:10.1.11]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:341) ~[tomcat-embed-core-10.1.11.jar:10.1.11]
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:391) ~[tomcat-embed-core-10.1.11.jar:10.1.11]
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:63) ~[tomcat-embed-core-10.1.11.jar:10.1.11]
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:894) ~[tomcat-embed-core-10.1.11.jar:10.1.11]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1740) ~[tomcat-embed-core-10.1.11.jar:10.1.11]
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:52) ~[tomcat-embed-core-10.1.11.jar:10.1.11]
    at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191) ~[tomcat-embed-core-10.1.11.jar:10.1.11]
    at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659) ~[tomcat-embed-core-10.1.11.jar:10.1.11]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) ~[tomcat-embed-core-10.1.11.jar:10.1.11]
    at java.base/java.lang.Thread.run(Thread.java:842) ~[na:na]

 抛出这个异常后，先进事务的操作没有生效，后面进事务的修改保留下来了（生效了。）。