Mastering Parallel Gateways in Activiti 7 with Spring Boot: A Step‑by‑Step Guide

Environment: Springboot 2.3.12.RELEASE + Activiti 7.1.0.M6

This article introduces the use of parallel gateways.

Overview

A parallel gateway allows a process to split into multiple concurrent branches and later merge them back into a single flow.

It has two functions: branching and merging .

Branching creates a concurrent branch for each outgoing sequence flow.

Merging combines multiple incoming branches into one outgoing flow.

The main difference from an exclusive gateway is that a parallel gateway ignores any conditions on the outgoing flows.

Example

The following reimbursement approval example demonstrates the branching and merging capabilities of a parallel gateway.

Four user tasks are defined, each with a dynamic assignee.

The "Employee reimbursement" task creates two parallel branches for approval by a deputy manager and a manager. After both approvals, the gateway merges and the flow proceeds to the "General manager".

Process definition (BPMN XML)

<code>&lt;?xml version="1.0" encoding="UTF-8"?&gt;
&lt;definitions xmlns="http://www.omg.org/spec/BPMN/20100524/MODEL" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:activiti="http://activiti.org/bpmn" xmlns:bpmndi="http://www.omg.org/spec/BPMN/20100524/DI" xmlns:omgdc="http://www.omg.org/spec/DD/20100524/DC" xmlns:omgdi="http://www.omg.org/spec/DD/20100524/DI" typeLanguage="http://www.w3.org/2001/XMLSchema" expressionLanguage="http://www.w3.org/1999/XPath" targetNamespace="http://www.activiti.org/test"&gt;
  &lt;process id="ps" name="ps" isExecutable="true"&gt;
    &lt;startEvent id="startEvent" name="开始"/&gt;
    &lt;parallelGateway id="parallelgateway" name="并行执行"/&gt;
    &lt;userTask id="usertask1" name="副经理" activiti:assignee="${fjl}"/&gt;
    &lt;userTask id="usertask2" name="经理" activiti:assignee="${jl}"/&gt;
    &lt;parallelGateway id="parallelgateway1" name="Parallel Gateway"/&gt;
    &lt;sequenceFlow id="flow4" sourceRef="parallelgateway" targetRef="usertask1"/&gt;
    &lt;sequenceFlow id="flow5" sourceRef="parallelgateway" targetRef="usertask2"/&gt;
    &lt;sequenceFlow id="flow6" sourceRef="usertask1" targetRef="parallelgateway1"/&gt;
    &lt;sequenceFlow id="flow7" sourceRef="usertask2" targetRef="parallelgateway1"/&gt;
    &lt;userTask id="usertask3" name="总经理" activiti:assignee="${zjl}"/&gt;
    &lt;sequenceFlow id="flow8" sourceRef="parallelgateway1" targetRef="usertask3"/&gt;
    &lt;endEvent id="endevent1" name="End"/&gt;
    &lt;sequenceFlow id="flow9" sourceRef="usertask3" targetRef="endevent1"/&gt;
    &lt;userTask id="usertask4" name="员工报销单" activiti:assignee="${userId}"/&gt;
    &lt;sequenceFlow id="flow10" sourceRef="usertask4" targetRef="parallelgateway"/&gt;
    &lt;sequenceFlow id="flow11" sourceRef="startEvent" targetRef="usertask4"/&gt;
  &lt;/process&gt;
  &lt;!-- ... --&gt;
&lt;/definitions&gt;</code>

Start Process

<code>@GetMapping("/start")
public R startProcess(String processDefinitionId, String userId) {
    Map<String, Object> variables = new HashMap<>();
    variables.put("userId", userId);
    // start process instance
    ProcessInstance instance = ps.startProcessInstanceAssignVariables(processDefinitionId, variables);
    // set next assignees
    variables.put("fjl", "20000");
    variables.put("jl", "20001");
    ps.executionTask(variables, instance.getId());
    return R.success();
}</code>

Query Tasks

<code>@GetMapping("/tasks")
public R myTasks(String userId) {
    List<Task> list = ps.queryTasks(userId);
    List<Map<String, Object>> result = list.stream().map(task -> {
        Map<String, Object> res = new HashMap<>();
        res.put("id", task.getId());
        res.put("assignee", task.getAssignee());
        res.put("createTime", task.getCreateTime());
        res.put("bussinessKey", task.getBusinessKey());
        res.put("category", task.getCategory());
        res.put("dueDate", task.getDueDate());
        res.put("desc", task.getDescription());
        res.put("name", task.getName());
        res.put("owner", task.getOwner());
        res.put("instanceId", task.getProcessInstanceId());
        res.put("variables", task.getProcessVariables());
        res.put("state", task.isSuspended());
        return res;
    }).collect(Collectors.toList());
    return R.success(result);
}</code>

Approve Task

<code>@GetMapping("/approve")
public R approve(@RequestParam Map<String, Object> variables) {
    String instanceId = (String) variables.remove("instanceId");
    if (StringUtils.isEmpty(instanceId)) {
        return R.failure("未知任务");
    }
    ps.executionTask(variables, instanceId);
    return R.success();
}</code>

Runtime tables (act_ru_task, act_ru_execution) show the state of tasks after each approval step, illustrating how the parallel gateway merges branches only after both deputy manager and manager have approved.

Finally, the process ends when the general manager approves, demonstrating the simple branching and merging behavior of parallel gateways.