Flowable Process Engine是如何启动的？

flowable-spring-boot-starter-process导入了flowable-spring-boot-autoconfigure

flowable-spring-boot-starter-process中只有一个pom.xml，其中pom.xml会导入相关的依赖

spring-boot-autoconfigure中配置类会启动引擎

src/main/resources/META-INF/spring/org.springframework.boot.autoconfigure.AutoConfiguration.imports中定义了哪些配置类，Spring Boot在启动时会去加载这些配置

加载的过程又可以细分为两部分

1. ProcessEngineAutoConfiguration负责加载好引擎的配置
2. ProcessEngineServicesAutoConfiguration负责根据ProcessEngineAutoConfiguration加载好的配置构建引擎

ProcessEngineAutoConfiguration

调用链：

1. springProcessEngineConfiguration方法加载SpringProcessEngineConfiguration
2. processEngineConfigurator方法加载ProcessEngineConfigurator

ProcessEngineServicesAutoConfiguration

调用链：

1. ProcessEngineServicesAutoConfiguration.StandaloneEngineConfiguration.processEngine方法创建ProcessEngineFactoryBean
2. ProcessEngineFactoryBean根据
3. Spring Boot框架调用ProcessEngineFactoryBean的getObject方法构建Process Engine
   在getObject方法中，会调用buildProcessEngine构建Process Engine