流程引擎

基本概念：
BPMI：The Business Process Management Initiative
BPMN：Business Process Modeling Notation。业务流程建模符号标准
CMMN: Case Management Model and Notation.案例管理模型和符号
DMN: Decision Model and Notation
Form Engine: 表单引擎

jbpm
JBoss -》Java Business Process Management-》Hibernate管理数据库-》
jBPM5则基于Drools Flow

XJR

Activiti5 -》依赖mybatis
Activiti5是jBPM4的衍生

jBPM4
|--衍生 Activiti5
|--衍生 flowable

flowable
https://blog.csdn.net/qq_35098526/article/details/87818988
https://www.jianshu.com/p/571ce598177e

ACT_RE_: 'RE' stands for repository
ACT_RU_: 'RU' stands for runtime
ACT_HI_: 'HI' stands for history
ACT_GE_: general data

//It deals with starting new process instances of process definitions. 
RuntimeService runtimeService = processEngine.getRuntimeService();

//This service offers operations for managing and manipulating deployments and process definitions. 
RepositoryService repositoryService = processEngine.getRepositoryService();

//Tasks that need to be performed by human users of the system
TaskService taskService = processEngine.getTaskService();

//The ManagementService is typically not needed when coding custom application using Flowable. It allows the retrieval of //information about the database tables and table metadata. Furthermore, it exposes query capabilities and management //operations for jobs. 
ManagementService managementService = processEngine.getManagementService();

//The IdentityService is pretty simple. It supports the management (creation, update, deletion, querying, …​) of groups and users.
//It is important to understand that Flowable actually doesn’t do any checking on users at runtime.
IdentityService identityService = processEngine.getIdentityService();

//The HistoryService exposes all historical data gathered by the Flowable engine. 
HistoryService historyService = processEngine.getHistoryService();

//The FormService is an optional service. 
//This service introduces the concept of a start form and a task form. 
FormService formService = processEngine.getFormService();

//The DynamicBpmnService can be used to change part of the process definition without needing to redeploy it.
DynamicBpmnService dynamicBpmnService = processEngine.getDynamicBpmnService();

a process definition is a Java counterpart of the BPMN 2.0 process.It is a representation of the structure and behavior of each of the steps of a process.
Variables:A process instance can have variables.stored in ACT_RU_VARIABLE
executions:which are specific pointers to where the process is active.
variables can be set local for a given execution

void setVariable(String executionId, String variableName, Object value);
void setVariable Local*String executionId, String variableName, Object value);

Transient variables are variables that behave like regular variables, but are not persisted.
A transient variable can only be accessed before the next 'wait state' in the process definition. Note that an async activity is also a 'wait state' in this definition!
A transient variable shadows a persistent variable with the same name.

UEL stands for Unified Expression Language and is part of the EE6 specification.
By default, all process variables are available to use.Also, all spring-beans (if using Spring) are available to use in expressions.
value-expression and method-expression

spring

1、engine as bean
2、join transaction together
3、expression ref beans
4、automatic resource deploy if needed

event

Start events are always catching.
An end event is always throwing.
Boundary events are catching events that are attached to an activity (a boundary event can never be throwing).
boundary timer events are only fired when the async executor is enabled.

Sequence Flow

Conditional sequence flow
Default sequence flow

Gateways

Exclusive Gateway
Parallel Gateway which allows you to fork into multiple paths of execution or join multiple incoming paths of execution.
Inclusive Gateway：take more than one sequence flow after value ;
Event-based Gateway

tasks

User Task
Script Task
Java Service Task
Web Service Task
Business Rule Task -> drools.规则引擎 JBoss -》drools -》rete算法：空间换时间-》reteOO改进算法
Email Task
Http Task
Mule Task -> Mule ESB -> 介绍https://www.cnblogs.com/enjoyingsoft/p/10132360.html; 官网https://www.mulesoft.com/
Camel Task -> https://camel.apache.org -> Camel is an Open Source integration framework that empowers you to quickly and easily integrate various systems consuming or producing data.
Manual Task
Java Receive Task
Shell Task
External Worker Task
Execution listener
Multi-instance -> instance for each loop
Compensation Handlers

Sub-Processes

Sub-Process
Event Sub-Process -> An Event Sub-Process can be visualized as an embedded sub-process
Transaction sub-process -> A transaction sub-process is an embedded sub-process that can be used to group multiple activities to a transaction. A transaction sub-process is visualized as a an embedded sub-process with a double outline.
Call activity -> The difference is that the call activity references a process that is external to the process definition, whereas the sub-process is embedded within the original process definition. The main use case for the call activity is to have a reusable process definition that can be called from multiple other process definitions.

History

HistoricProcessInstances
HistoricVariableInstances -> the latest value of a process variable or task variable.
HistoricActivityInstances
HistoricTaskInstances
HistoricIdentityLinks
HistoricDetails

history levels

none, activity, audit, full

Identity management

User and UserEntity
Group and GroupEntity
MembershipEntity
Privilege and PrivilegeEntity
Token and TokenEntity

when disable IDM, This means that no user and group queries can be used, and candidate groups in a task query can not be retrieved for a user.