在eclipse配置一个简单的activiti项目，配置的是mysql数据库，报错如下：
SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder". SLF4J: Defaulting to no-operation (NOP) logger implementation SLF4J: See http://www.slf4j.org/codes.html#StaticLoggerBinder for further details. Exception in thread "main" org.activiti.engine.ActivitiException: Could not update Activiti database schema: unknown version from database: ‘5.18.0.1‘ at org.activiti.engine.impl.db.DbSqlSession.dbSchemaUpdate(DbSqlSession.java:1007) at org.activiti.engine.impl.db.DbSqlSession.performSchemaOperationsProcessEngineBuild(DbSqlSession.java:1385) 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:413) at com.pcitc.activiti.FirstActiviti.main(FirstActiviti.java:18)
最后网上搜索了很多答案，都解决不了。最后发现是我之前运行过activiti的样例代码activiti-explorer,并且把数据库配置为mysql，这个样例程序已经在数据库里面建好了表导致的。于是我把之前的表删除了，问题就没有了，但是不知道是啥原因？？？只能分析下源代码了。
activiti集成spring异常(DbSqlSession)
原文：http://www.cnblogs.com/longshiyVip/p/5111583.html