简介

flowable engine一共有5种：App, CMMN, DMN, Form, Process(即BPMN)。

flowable-spring-boot-starter提供了零配置集成flowable的功能，主要包括各类型engine的自动配置、流程/表单定义自动部署，其次还有rest-api，spring boot aucuator集成等。

这篇文章主要是解析flowable在spring boot环境下的启动流程，不涉及flowable内部原理。

flowable相关的AutoConfiguration

# flowable-spring-boot-autoconfigure: spring.factories

org.springframework.boot.env.EnvironmentPostProcessor=\
  org.flowable.spring.boot.environment.FlowableDefaultPropertiesEnvironmentPostProcessor,\
  org.flowable.spring.boot.environment.FlowableLiquibaseEnvironmentPostProcessor

# Flowable auto-configurations

org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
    org.flowable.spring.boot.actuate.info.FlowableInfoAutoConfiguration,\
    org.flowable.spring.boot.EndpointAutoConfiguration,\
    org.flowable.spring.boot.RestApiAutoConfiguration,\
    org.flowable.spring.boot.app.AppEngineServicesAutoConfiguration,\
    org.flowable.spring.boot.app.AppEngineAutoConfiguration,\
    org.flowable.spring.boot.ProcessEngineServicesAutoConfiguration,\
    org.flowable.spring.boot.ProcessEngineAutoConfiguration,\
    org.flowable.spring.boot.FlowableJpaAutoConfiguration,\
    org.flowable.spring.boot.form.FormEngineAutoConfiguration,\
    org.flowable.spring.boot.form.FormEngineServicesAutoConfiguration,\
    org.flowable.spring.boot.content.ContentEngineAutoConfiguration,\
    org.flowable.spring.boot.content.ContentEngineServicesAutoConfiguration,\
    org.flowable.spring.boot.dmn.DmnEngineAutoConfiguration,\
    org.flowable.spring.boot.dmn.DmnEngineServicesAutoConfiguration,\
    org.flowable.spring.boot.idm.IdmEngineAutoConfiguration,\
    org.flowable.spring.boot.idm.IdmEngineServicesAutoConfiguration,\
    org.flowable.spring.boot.cmmn.CmmnEngineAutoConfiguration,\
    org.flowable.spring.boot.cmmn.CmmnEngineServicesAutoConfiguration,\
    org.flowable.spring.boot.ldap.FlowableLdapAutoConfiguration,\
    org.flowable.spring.boot.FlowableSecurityAutoConfiguration

看起来比较多，不过大多数AutoConfiguration逻辑还是比较简单的。

engine自动配置

各engine的配置方式大同小异，以ProcessEngine为例，其涉及到的AutoConfiguration主要是

ProcessEngineAutoConfiguration
ProcessEngineServicesAutoConfiguration

ProcessEngineAutoConfiguration

ProcessEngineAutoConfiguration类图

从红框部分可以看到，在ProcessEngineAutoConfiguration中配置了一个类型为SpringProcessEngineConfiguration的bean，其类图如下

可知，SpringProcessEngineConfiguration是ProcessEngineConfiguration的子类，而ProcessEngineConfiguration正是用于创建ProcessEngine的类。

不过这里只是注册了一个bean，并没有调用其buildProcessEngine()方法来创建ProcessEngine。ProcessEngine实例是在ProcessEngineFactoryBean中创建的。

ProcessEngineServicesAutoConfiguration

这个AutoConfiguration主要负责配置ProcessEngineFactoryBean及各个Service（RuntimeService, RepositoryService, TaskService等）。

各Service的配置比较简单，主要来看看ProcessEngineFactoryBean

ProcessEngineFactoryBean

需要注意的是ProcessEngineFactoryBean是在内部类ProcessEngineServicesAutoConfiguration#StandaloneEngineConfiguration中注册的。

这是一个FactoryBean，我们知道Spring通过FactoryBean的getObject()方法来创建bean，来看看其代码

// ProcessEngineFactoryBean.java
public class ProcessEngineFactoryBean implements FactoryBean<ProcessEngine>, DisposableBean, ApplicationContextAware {
    protected ProcessEngineConfigurationImpl processEngineConfiguration;
    @Override
    public ProcessEngine getObject() throws Exception {
        // 省略无关代码...
        this.processEngine = processEngineConfiguration.buildProcessEngine();
        return this.processEngine;
    }
}

可以看到，ProcessEngineFactoryBean通过调用processEngineConfiguration.buildProcessEngine()创建了ProcessEngine的实例。

对于processEngineConfiguration这个对象的构建，可以参考ProcessEngineAutoConfiguration

自动部署

flowable spring boot starter能够自动将classpath的相关目录（如processes, forms）下的资源自动部署。

不同的engine逻辑大同小异，以ProcessEngine为例，其核心在于SpringProcessEngineConfiguration这个类。

SpringProcessEngineConfiguration实现了spring的SmartLifecycle接口，相关代码如下

// SpringProcessEngineConfiguration.java
@Override
public void start() {
    synchronized (lifeCycleMonitor) {
        if (!isRunning()) {
            // 遍历engines实例进行部署
            enginesBuild.forEach(name -> autoDeployResources(ProcessEngines.getProcessEngine(name)));
            running = true;
        }
    }
}

@Override
public void stop() {
    synchronized (lifeCycleMonitor) {
        running = false;
    }
}

@Override
public boolean isRunning() {
    return running;
}

其中start方法正是对process engines所需要的资源进行自动部署，会在spring应用完成初始化后进行回调。

来看看autoDeployResources方法

// SpringProcessEngineConfiguration.java
protected Resource[] deploymentResources = new Resource[0];

protected void autoDeployResources(ProcessEngine processEngine) {
    if (deploymentResources != null && deploymentResources.length > 0) {
        final AutoDeploymentStrategy strategy = getAutoDeploymentStrategy(deploymentMode);      // 选择部署策略
        strategy.deployResources(deploymentName, deploymentResources, processEngine.getRepositoryService());
    }
}

字段deploymentResources的值是关键，通过调试，发现该字段是在ProcessEngineAutoConfiguration中进行赋值的

// ProcessEngineAutoConfiguration
@Bean
@ConditionalOnMissingBean
public SpringProcessEngineConfiguration springProcessEngineConfiguration(DataSource dataSource, PlatformTransactionManager platformTransactionManager,
        @Process ObjectProvider<IdGenerator> processIdGenerator,
        ObjectProvider<IdGenerator> globalIdGenerator,
        @ProcessAsync ObjectProvider<AsyncExecutor> asyncExecutorProvider,
        @ProcessAsyncHistory ObjectProvider<AsyncExecutor> asyncHistoryExecutorProvider) throws IOException {

    SpringProcessEngineConfiguration conf = new SpringProcessEngineConfiguration();

    // 根据配置的规则找到相关的资源
    List<Resource> resources = this.discoverDeploymentResources(
        flowableProperties.getProcessDefinitionLocationPrefix(),
        flowableProperties.getProcessDefinitionLocationSuffixes(),
        flowableProperties.isCheckProcessDefinitions()
    );

    if (resources != null && !resources.isEmpty()) {
        conf.setDeploymentResources(resources.toArray(new Resource[0]));
        conf.setDeploymentName(flowableProperties.getDeploymentName());
    }

    // ...省略无关代码

    return conf;
}

TODO LIST

List<EngineConfigurationConfigurer>

Taccisum's blog 😉

flowable启动流程解析（spring boot）

简介