(1). 概述
在前面,分析到:ProcessEngine.buildProcessEngine就没有继续往下分析, 在这一小节,我将对:ProcessEngine.buildProcessEngine方法进入深剖.
(2). ProcessEngine.buildProcessEngine
在这里,只针对init方法中,我认为比较重要(Camunda代码写得优秀)的地方进行剖析.
public ProcessEngine buildProcessEngine() {
// 3. 调用init()方法
init();
processEngine = new ProcessEngineImpl(this);
invokePostProcessEngineBuild(processEngine);
return processEngine;
}
(3). ProcessEngine.init
init方法很复杂,我只挑几个重要的点进行分析.
- initDataSource(数据源初始化).
- initCommandExecutors(命令执行器初始化,典型的:责任链模式和命令模式).
- initEventHandlers(事件处理器,典型的:观察者模式).
- initDeployers(流程部署/流程解析的入口[BpmnParse]),这一部份也不会深剖,会另开一篇来分析.
protected void init() {
// Camunda的新功能,允许用户对PorcessEngine进行定制
// 类似于Spring中定义的一些回调函数.
// 扩展:ProcessEnginePlugin接口
invokePreInit();
// 设置默认的字符串
initDefaultCharset();
initHistoryLevel();
initHistoryEventProducer();
initCmmnHistoryEventProducer();
initDmnHistoryEventProducer();
initHistoryEventHandler();
initExpressionManager();
initBeans();
initArtifactFactory();
initFormEngines();
initFormTypes();
initFormFieldValidators();
initScripting();
initDmnEngine();
initBusinessCalendarManager();
initCommandContextFactory();
initTransactionContextFactory();
// Database type needs to be detected before CommandExecutors are initialized
// *******************************************************************
// 4. 数据源初始化
// *******************************************************************
initDataSource();
// *******************************************************************
// 5. 命令执行器初始化
// *******************************************************************
initCommandExecutors();
// xxxService初始化
initServices();
// ID生成策略
initIdGenerator();
initFailedJobCommandFactory();
// *******************************************************************
// 7. 初始化部署
// *******************************************************************
initDeployers();
initJobProvider();
initExternalTaskPriorityProvider();
initBatchHandlers();
initJobExecutor();
// *******************************************************************
// 事务管理器
// *******************************************************************
initTransactionFactory();
// MyBatis
initSqlSessionFactory();
initIdentityProviderSessionFactory();
initSessionFactories();
initValueTypeResolver();
initTypeValidator();
initSerialization();
initJpa();
initDelegateInterceptor();
// *******************************************************************
// 6. 事件处理器初始化
// *******************************************************************
initEventHandlers();
initProcessApplicationManager();
initCorrelationHandler();
initConditionHandler();
initIncidentHandlers();
initPasswordDigest();
initDeploymentRegistration();
initDeploymentHandlerFactory();
initResourceAuthorizationProvider();
initPermissionProvider();
initHostName();
initMetrics();
initTelemetry();
initMigration();
initCommandCheckers();
initDefaultUserPermissionForTask();
initHistoryRemovalTime();
initHistoryCleanup();
initInvocationsPerBatchJobByBatchType();
initAdminUser();
initAdminGroups();
initPasswordPolicy();
invokePostInit();
}// end init
protected void invokePreInit() {
for (ProcessEnginePlugin plugin : processEnginePlugins) {
LOG.pluginActivated(plugin.toString(), getProcessEngineName());
plugin.preInit(this);
}
} //end invokePreInit
protected void invokePostInit() {
for (ProcessEnginePlugin plugin : processEnginePlugins) {
plugin.postInit(this);
}
} //end invokePostInit
(4). ProcessEngineConfigurationImpl.initDataSource
从这里的代码分析能看出来,连接池是复用了MyBatis的.从性能角度着想:建议自己配置:DataSource.
// domain
protected String databaseType;
protected String databaseVendor;
protected String databaseVersion;
protected String databaseSchemaUpdate = DB_SCHEMA_UPDATE_FALSE;
protected String jdbcDriver = "org.h2.Driver";
protected String jdbcUrl = "jdbc:h2:tcp://localhost/activiti";
protected String jdbcUsername = "sa";
protected String jdbcPassword = "";
protected String dataSourceJndiName = null;
protected int jdbcMaxActiveConnections;
protected int jdbcMaxIdleConnections;
protected int jdbcMaxCheckoutTime;
protected int jdbcMaxWaitTime;
protected boolean jdbcPingEnabled = false;
protected String jdbcPingQuery = null;
protected int jdbcPingConnectionNotUsedFor;
protected DataSource dataSource;
// initDataSource
protected void initDataSource() {
if (dataSource == null) {
// 判断数据源是否为:jndi,如果是jndi配置,则通过:InitialContext去获取:DataSource
if (dataSourceJndiName != null) {
try {
dataSource = (DataSource) new InitialContext().lookup(dataSourceJndiName);
} catch (Exception e) {
throw new ProcessEngineException("couldn't lookup datasource from " + dataSourceJndiName + ": " + e.getMessage(), e);
}
} else if (jdbcUrl != null) { // 查看是否有配置jdbcUrl
if ((jdbcDriver == null) || (jdbcUrl == null) || (jdbcUsername == null)) {
throw new ProcessEngineException("DataSource or JDBC properties have to be specified in a process engine configuration");
}
// 在这里引用的是:org.apache.ibatis.datasource.pooled.PooledDataSource
// 内部实则为:org.apache.ibatis.datasource.unpooled.UnpooledDataSource.UnpooledDataSource
// 这时要注意了:建议换成自己的:dataSource
PooledDataSource pooledDataSource =
new PooledDataSource(ReflectUtil.getClassLoader(), jdbcDriver, jdbcUrl, jdbcUsername, jdbcPassword);
if (jdbcMaxActiveConnections > 0) {
pooledDataSource.setPoolMaximumActiveConnections(jdbcMaxActiveConnections);
}
if (jdbcMaxIdleConnections > 0) {
pooledDataSource.setPoolMaximumIdleConnections(jdbcMaxIdleConnections);
}
if (jdbcMaxCheckoutTime > 0) {
pooledDataSource.setPoolMaximumCheckoutTime(jdbcMaxCheckoutTime);
}
if (jdbcMaxWaitTime > 0) {
pooledDataSource.setPoolTimeToWait(jdbcMaxWaitTime);
}
if (jdbcPingEnabled == true) {
pooledDataSource.setPoolPingEnabled(true);
if (jdbcPingQuery != null) {
pooledDataSource.setPoolPingQuery(jdbcPingQuery);
}
pooledDataSource.setPoolPingConnectionsNotUsedFor(jdbcPingConnectionNotUsedFor);
}
dataSource = pooledDataSource;
}
if (dataSource instanceof PooledDataSource) {
// ACT-233: connection pool of Ibatis is not properely initialized if this is not called!
((PooledDataSource) dataSource).forceCloseAll();
}
}// end if
// 这一步是根据Connection获得所连接的是:MySQL/MariaDB/PostgreSQL/CockroachDB
if (databaseType == null) {
initDatabaseType();
}
}// end initDataSource
(5). ProcessEngineConfigurationImpl.initCommandExecutors
// domain
protected List<CommandInterceptor> customPreCommandInterceptorsTxRequired;
protected List<CommandInterceptor> customPostCommandInterceptorsTxRequired;
protected List<CommandInterceptor> commandInterceptorsTxRequired;
protected List<CommandInterceptor> customPreCommandInterceptorsTxRequiresNew;
protected List<CommandInterceptor> customPostCommandInterceptorsTxRequiresNew;
protected List<CommandInterceptor> commandInterceptorsTxRequiresNew;
protected CommandExecutor commandExecutorTxRequiresNew;
protected CommandExecutor commandExecutorSchemaOperations;
protected CommandExecutor commandExecutorTxRequired;
protected CommandInterceptor actualCommandExecutor;
// methods
protected void initCommandExecutors() {
// 5.1 创建:CommandExecutorImpl
initActualCommandExecutor();
// 5.2 创建Command拦截器(针对Require传播行为)
initCommandInterceptorsTxRequired();
// 5.3 对5.2步产生的List<CommandInterceptor>组合成链表
initCommandExecutorTxRequired();
// 5.4 创建Command拦截器(针对RequireNew传播行为)
initCommandInterceptorsTxRequiresNew();
// 5.5 对5.4步产生的List<CommandInterceptor>组合成链表
initCommandExecutorTxRequiresNew();
initCommandExecutorDbSchemaOperations();
}// end initCommandExecutors
// 5.1 创建:CommandExecutorImpl
protected void initActualCommandExecutor() {
// 创建真实的Command实现类
actualCommandExecutor = new CommandExecutorImpl();
} //end initActualCommandExecutor
// 5.2 创建Command拦截器
// 这一步主要是配置:CommandInterceptor
// 可以简化理解为这样:
// commandInterceptorsTxRequired = new ArrayList(
// customPreCommandInterceptorsTxRequired ,
// getDefaultCommandInterceptorsTxRequired() ,
// customPostCommandInterceptorsTxRequired ,
// actualCommandExecutor
// );
protected void initCommandInterceptorsTxRequired() {
if (commandInterceptorsTxRequired == null) { // true
// customPreCommandInterceptors
if (customPreCommandInterceptorsTxRequired != null) {
commandInterceptorsTxRequired = new ArrayList<>(customPreCommandInterceptorsTxRequired);
} else {
// 初始化(commandInterceptorsTxRequired)
commandInterceptorsTxRequired = new ArrayList<>();
}
// defaultCommandInterceptors
commandInterceptorsTxRequired.addAll(getDefaultCommandInterceptorsTxRequired());
// postCommandInterceptors
if (customPostCommandInterceptorsTxRequired != null) {
commandInterceptorsTxRequired.addAll(customPostCommandInterceptorsTxRequired);
}
// actualCommandExecutor
commandInterceptorsTxRequired.add(actualCommandExecutor);
}
}//end initCommandInterceptorsTxRequired
// 5.3 对5.2步产生的:List<CommandInterceptor>(commandInterceptorsTxRequired)集合,组合成链表
// CommandInterceptor是一个链表结构.内部持有下一个:CommandExecutor
protected void initCommandExecutorTxRequired() {
if (commandExecutorTxRequired == null) { //commandExecutorTxRequired是链表结构的:CommandInterceptor
commandExecutorTxRequired = initInterceptorChain(commandInterceptorsTxRequired);
}
}// end initCommandExecutorTxRequired
protected CommandInterceptor initInterceptorChain(List<CommandInterceptor> chain) {
// 集合不能为空
if (chain == null || chain.isEmpty()) {
throw new ProcessEngineException("invalid command interceptor chain configuration: " + chain);
}
// *****************************************************************
// 把集合,转换成链表.
// *****************************************************************
for (int i = 0; i < chain.size() - 1; i++) {
chain.get(i).setNext(chain.get(i + 1));
}
// 返回链表的首元素:CommandInterceptor
return chain.get(0);
}// end initInterceptorChain
protected void initCommandInterceptorsTxRequiresNew() {
if (commandInterceptorsTxRequiresNew == null) {
if (customPreCommandInterceptorsTxRequiresNew != null) {
commandInterceptorsTxRequiresNew = new ArrayList<>(customPreCommandInterceptorsTxRequiresNew);
} else {
commandInterceptorsTxRequiresNew = new ArrayList<>();
}
commandInterceptorsTxRequiresNew.addAll(getDefaultCommandInterceptorsTxRequiresNew());
if (customPostCommandInterceptorsTxRequiresNew != null) {
commandInterceptorsTxRequiresNew.addAll(customPostCommandInterceptorsTxRequiresNew);
}
commandInterceptorsTxRequiresNew.add(actualCommandExecutor);
}
} //end initCommandInterceptorsTxRequiresNew
protected void initCommandExecutorTxRequiresNew() {
if (commandExecutorTxRequiresNew == null) {
commandExecutorTxRequiresNew = initInterceptorChain(commandInterceptorsTxRequiresNew);
}
}//end initCommandExecutorTxRequiresNew
protected void initCommandExecutorDbSchemaOperations() {
if (commandExecutorSchemaOperations == null) {
commandExecutorSchemaOperations = commandExecutorTxRequired;
}
} // end initCommandExecutorDbSchemaOperations
(6). ProcessEngineConfigurationImpl.initEventHandlers
// domain
protected Map<String, EventHandler> eventHandlers;
protected List<EventHandler> customEventHandlers;
// methods
protected void initEventHandlers() {
if (eventHandlers == null) {
// 对:eventHandlers进行初始化
eventHandlers = new HashMap<>();
// 创建:SignalEventHandler
SignalEventHandler signalEventHander = new SignalEventHandler();
eventHandlers.put(signalEventHander.getEventHandlerType(), signalEventHander);
// 创建:CompensationEventHandler
CompensationEventHandler compensationEventHandler = new CompensationEventHandler();
eventHandlers.put(compensationEventHandler.getEventHandlerType(), compensationEventHandler);
// 创建:EventType.MESSAGE
EventHandler messageEventHandler = new EventHandlerImpl(EventType.MESSAGE);
eventHandlers.put(messageEventHandler.getEventHandlerType(), messageEventHandler);
// 创建:ConditionalEventHandler
EventHandler conditionalEventHandler = new ConditionalEventHandler();
eventHandlers.put(conditionalEventHandler.getEventHandlerType(), conditionalEventHandler);
} // end if
// 配置自定义的EventHandler
// 要注意:要是想覆盖系统的Event,只需要自定义的EventHandler的Type与系统的相当即可.
if (customEventHandlers != null) {
for (EventHandler eventHandler : customEventHandlers) {
eventHandlers.put(eventHandler.getEventHandlerType(), eventHandler);
}
}// end if
} // end initEventHandlers
(7). ProcessEngineConfigurationImpl.initDeployers
// domain
protected List<Deployer> customPreDeployers;
protected List<Deployer> customPostDeployers;
protected List<Deployer> deployers;
protected DeploymentCache deploymentCache;
protected CacheFactory cacheFactory;
protected int cacheCapacity = 1000;
protected boolean enableFetchProcessDefinitionDescription = true;
// methods
protected void initDeployers() {
if (this.deployers == null) {
// 初始化:deployers
this.deployers = new ArrayList<>();
// 前置自定义部署组件
if (customPreDeployers != null) {
this.deployers.addAll(customPreDeployers);
}
// 默认的部署组件
this.deployers.addAll(getDefaultDeployers());
// 后置自定义部署组件
if (customPostDeployers != null) {
this.deployers.addAll(customPostDeployers);
}
}// end if
if (deploymentCache == null) {
List<Deployer> deployers = new ArrayList<>();
if (customPreDeployers != null) {
deployers.addAll(customPreDeployers);
}
deployers.addAll(getDefaultDeployers());
if (customPostDeployers != null) {
deployers.addAll(customPostDeployers);
}
// 初始化缓存工厂(工厂模式)
initCacheFactory();
deploymentCache = new DeploymentCache(cacheFactory, cacheCapacity);
deploymentCache.setDeployers(deployers);
} // end if
}
protected Collection<? extends Deployer> getDefaultDeployers() {
List<Deployer> defaultDeployers = new ArrayList<>();
// getBpmnDeployer()
BpmnDeployer bpmnDeployer = getBpmnDeployer();
defaultDeployers.add(bpmnDeployer);
// 以下是cmmn/dmn了
if (isCmmnEnabled()) {
CmmnDeployer cmmnDeployer = getCmmnDeployer();
defaultDeployers.add(cmmnDeployer);
}
if (isDmnEnabled()) {
DecisionRequirementsDefinitionDeployer decisionRequirementsDefinitionDeployer = getDecisionRequirementsDefinitionDeployer();
DecisionDefinitionDeployer decisionDefinitionDeployer = getDecisionDefinitionDeployer();
// the DecisionRequirementsDefinition cacheDeployer must be before the DecisionDefinitionDeployer
defaultDeployers.add(decisionRequirementsDefinitionDeployer);
defaultDeployers.add(decisionDefinitionDeployer);
}
return defaultDeployers;
}// end
protected BpmnDeployer getBpmnDeployer() {
BpmnDeployer bpmnDeployer = new BpmnDeployer();
bpmnDeployer.setExpressionManager(expressionManager);
bpmnDeployer.setIdGenerator(idGenerator);
if (bpmnParseFactory == null) {
bpmnParseFactory = new DefaultBpmnParseFactory();
}
// ***************************************************************************
// 创建:BpmnParser,它是流程定义解析的入口.内容比较多,会另外再抽一节进行剖析
// ***************************************************************************
BpmnParser bpmnParser = new BpmnParser(expressionManager, bpmnParseFactory);
if (preParseListeners != null) {
bpmnParser.getParseListeners().addAll(preParseListeners);
}
bpmnParser.getParseListeners().addAll(getDefaultBPMNParseListeners());
if (postParseListeners != null) {
bpmnParser.getParseListeners().addAll(postParseListeners);
}
bpmnDeployer.setBpmnParser(bpmnParser);
return bpmnDeployer;
} // end
(8). CommandExecutor类结构图解
(9). EventHandler类结构图解
