工作流主要解决的主要问题是：为了实现某个业务目标，利用计算机在多个参与者之间按某种预定规则自动传递文档、信息或者任务。
activiti官方提供了一个示例工程activiti-explorer.war,运行这个工程可以体验activiti的基本功能，了解工作流的基本使用。
本文中使用的是activiti-5.22.0的官方包,
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一、搭建开发环境
要运行示例工程，需要安装jdk8和tomcat。其中jdk需要jdk8或以上,tomcat我使用的是tomcat8,使用tomcat7时启动会报如下错误:
严重: Exception sending context initialized event to listener instance of class org.activiti.explorer.servlet.WebConfigurer org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'demoDataConfiguration': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: protected org.activiti.engine.IdentityService org.activiti.explorer.conf.DemoDataConfiguration.identityService; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'identityService' defined in class path resource [org/activiti/explorer/conf/ActivitiEngineConfiguration.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.activiti.engine.IdentityService]: Factory method 'identityService' threw exception; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'processEngine' defined in class path resource [org/activiti/explorer/conf/ActivitiEngineConfiguration.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.activiti.engine.ProcessEngine]: Factory method 'processEngine' threw exception; nested exception is java.lang.RuntimeException: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'processEngineFactoryBean': FactoryBean threw exception on object creation; nested exception is java.util.ServiceConfigurationError: org.activiti.engine.cfg.ProcessEngineConfigurator: org.activiti.management.jmx.JMXConfigurator not a subtype at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:334) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1202) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:537) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:476) at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:303) at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230) at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:299) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194) at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:755) at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:757) at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:480) at org.activiti.explorer.servlet.WebConfigurer.contextInitialized(WebConfigurer.java:40) at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:5197) at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5720) at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:145) at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:1018) at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:994) at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:662) at org.apache.catalina.startup.HostConfig.deployWAR(HostConfig.java:1127) at org.apache.catalina.startup.HostConfig$DeployWar.run(HostConfig.java:2020) at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:514) at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264) at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167) at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641) at java.base/java.lang.Thread.run(Thread.java:844)
