Build a Simple Leave Approval Workflow with Flowable and Spring Boot

1. Introduction to Flowable

Flowable is a lightweight Java‑based BPMN2.0 workflow engine that can deploy process definitions, start instances, query, and access runtime or historic data.

Another Java workflow engine is Activiti; mastering one makes the other easy.

2. Create Project

Start a Spring Boot project with Web and MySQL dependencies, then add the Flowable starter:

<code><dependency>
    <groupId>org.flowable</groupId>
    <artifactId>flowable-spring-boot-starter</artifactId>
    <version>6.7.2</version>
</dependency></code>

Configure the database in

application.yaml

:

<code>spring:
  datasource:
    username: root
    password: 123
    url: jdbc:mysql:///flowable?serverTimezone=Asia/Shanghai&amp;useSSL=false
</code>

When the application starts, Flowable automatically creates the required tables.

3. Design BPMN Diagram

Use the Flowable BPMN visualizer plugin for IntelliJ IDEA to create a BPMN file

ask_for_leave.bpmn20.xml

under

resources/processes

. The diagram includes a start event, user tasks for leave request, team‑lead approval, manager approval, exclusive gateways for decision branches, a service task for failure notification, and an end event.

The XML definition looks like:

<code><process id="ask_for_leave" name="ask_for_leave" isExecutable="true">
  <userTask id="leaveTask" name="请假" flowable:assignee="#{leaveTask}"/>
  <userTask id="zuzhangTask" name="组长审核" flowable:assignee="#{zuzhangTask}"/>
  <userTask id="managerTask" name="经理审核" flowable:assignee="#{managerTask}"/>
  <exclusiveGateway id="managerJudgeTask"/>
  <exclusiveGateway id="zuzhangJudeTask"/>
  <endEvent id="endLeave" name="结束"/>
  <startEvent id="startLeave" name="开始"/>
  <!-- sequence flows omitted for brevity -->
  <serviceTask id="sendMail" flowable:exclusive="true" name="发送失败提示"
               isForCompensation="true"
               flowable:class="org.javaboy.flowable.AskForLeaveFail"/>
</process>
</code>

<process>

: defines the whole workflow.

<startEvent>

: start node.

<endEvent>

: end node.

<userTask>

: approval tasks with

flowable:assignee

attribute.

<serviceTask>

: custom service execution.

<exclusiveGateway>

: decision point.

<sequenceFlow>

: connects nodes.

4. Implement API and Tests

4.1 View Process Diagram

REST endpoint to generate the current diagram image:

<code>@RestController
public class HelloController {
    @Autowired RuntimeService runtimeService;
    @Autowired TaskService taskService;
    @Autowired RepositoryService repositoryService;
    @Autowired ProcessEngine processEngine;

    @GetMapping("/pic")
    public void showPic(HttpServletResponse resp, String processId) throws Exception {
        ProcessInstance pi = runtimeService.createProcessInstanceQuery()
                                         .processInstanceId(processId)
                                         .singleResult();
        if (pi == null) return;
        List<Execution> executions = runtimeService.createExecutionQuery()
                                                   .processInstanceId(processId)
                                                   .list();
        List<String> activityIds = new ArrayList<>();
        for (Execution exe : executions) {
            activityIds.addAll(runtimeService.getActiveActivityIds(exe.getId()));
        }
        BpmnModel bpmnModel = repositoryService.getBpmnModel(pi.getProcessDefinitionId());
        ProcessEngineConfiguration engconf = processEngine.getProcessEngineConfiguration();
        ProcessDiagramGenerator diagramGenerator = engconf.getProcessDiagramGenerator();
        InputStream in = diagramGenerator.generateDiagram(bpmnModel, "png",
                activityIds, Collections.emptyList(),
                engconf.getActivityFontName(), engconf.getLabelFontName(),
                engconf.getAnnotationFontName(), engconf.getClassLoader(),
                1.0, false);
        OutputStream out = resp.getOutputStream();
        byte[] buf = new byte[1024];
        int len;
        while ((len = in.read(buf)) != -1) {
            out.write(buf, 0, len);
        }
        in.close(); out.close();
    }
}
</code>

4.2 Start a Process

<code>@Test
void askForLeave() {
    HashMap<String, Object> map = new HashMap<>();
    map.put("leaveTask", "1000");
    ProcessInstance pi = runtimeService.startProcessInstanceByKey("ask_for_leave", map);
    runtimeService.setVariable(pi.getId(), "name", "javaboy");
    runtimeService.setVariable(pi.getId(), "reason", "休息一下");
    runtimeService.setVariable(pi.getId(), "days", 10);
    logger.info("创建请假流程 processId：{}", pi.getId());
}
</code>

4.3 Submit to Team Lead

<code>@Test
void submitToZuzhang() {
    List<Task> list = taskService.createTaskQuery()
                                 .taskAssignee(staffId)
                                 .orderByTaskId().desc()
                                 .list();
    for (Task task : list) {
        Map<String, Object> map = new HashMap<>();
        map.put("zuzhangTask", "90");
        taskService.complete(task.getId(), map);
    }
}
</code>

4.4 Team‑Lead Approval

Approve:

<code>@Test
void zuZhangApprove() {
    List<Task> list = taskService.createTaskQuery()
                                 .taskAssignee(zuzhangId)
                                 .orderByTaskId().desc()
                                 .list();
    for (Task task : list) {
        Map<String, Object> map = new HashMap<>();
        map.put("managerTask", managerId);
        map.put("checkResult", "通过");
        taskService.complete(task.getId(), map);
    }
}
</code>

Reject:

<code>@Test
void zuZhangReject() {
    List<Task> list = taskService.createTaskQuery()
                                 .taskAssignee(zuzhangId)
                                 .orderByTaskId().desc()
                                 .list();
    for (Task task : list) {
        Map<String, Object> map = new HashMap<>();
        map.put("checkResult", "拒绝");
        taskService.complete(task.getId(), map);
    }
}
</code>

4.5 Manager Approval

Approve:

<code>@Test
void managerApprove() {
    List<Task> list = taskService.createTaskQuery()
                                 .taskAssignee(managerId)
                                 .orderByTaskId().desc()
                                 .list();
    for (Task task : list) {
        Map<String, Object> map = new HashMap<>();
        map.put("checkResult", "通过");
        taskService.complete(task.getId(), map);
    }
}
</code>

Reject:

<code>@Test
void managerReject() {
    List<Task> list = taskService.createTaskQuery()
                                 .taskAssignee(managerId)
                                 .orderByTaskId().desc()
                                 .list();
    for (Task task : list) {
        Map<String, Object> map = new HashMap<>();
        map.put("checkResult", "拒绝");
        taskService.complete(task.getId(), map);
    }
}
</code>

4.6 Failure Handling

If either approver rejects, the process follows the

serviceTask

sendMail

, which invokes

org.javaboy.flowable.AskForLeaveFail

:

<code>public class AskForLeaveFail implements JavaDelegate {
    @Override
    public void execute(DelegateExecution execution) {
        System.out.println("请假失败。。。");
    }
}
</code>

5. Summary

This simple leave‑approval example demonstrates how to set up Flowable in a Spring Boot application, design BPMN diagrams, deploy processes, visualize runtime state, and implement task handling logic.