Activiti学习之根据条件判断流程走向

在流程设计当中经常会遇到根据条件来判断流程走向的问题，Activiti中也给出了相应的实现方法：网关。
网关（Gateway）用于控制流程走向（在BPMN2.0规范中称为“执行令牌”）。根据功能不同可以划分为以下四种网关：
- 排他网关
- 并行网关
- 包容网关
- 事件网关
其中，排他网关（Exclusive Gateway）用来对流程中的走向进行建模。流程执行到该网关时，Activiti 根据设置的条件进行计算，当条件计算结果为true时，执行当前网关的输出流。

小提示：如果多个线路计算结果都为true，那么只会执行第一个，如果没有为true的值，会抛出异常。

排他网关在流程图当中的形象如下图所示：

下面介绍一下排他网关的使用方法。

1、绘制流程图

ExclusiveProcess.bpmn如下所示：

其中排他网关的三个输出线分别设置Condition值为：

${type == 1}${type == 2}${type == 3}

当表达式判断结果为true时会执行后面的系统任务。
三个系统任务分别设置成如图所示：

三个系统任务的Task type 设为Expression，Expression选项中分别填入

${resumeService.showTask1()}${resumeService.showTask2()}${resumeService.showTask3()}

流程图的XML代码如下：

<?xml version="1.0" encoding="UTF-8"?><definitions xmlns="http://www.omg.org/spec/BPMN/20100524/MODEL" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 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">  <process id="exclusiveProcess" name="ExclusiveProcess.bpmn" isExecutable="true">    <startEvent id="startevent1" name="Start"></startEvent>    <exclusiveGateway id="exclusivegateway1" name="Exclusive Gateway"></exclusiveGateway>    <sequenceFlow id="flow1" sourceRef="startevent1" targetRef="exclusivegateway1"></sequenceFlow>    <serviceTask id="servicetask1" name="Service Task1" activiti:expression="${resumeService.showTask1()}"></serviceTask>    <sequenceFlow id="flow2" sourceRef="exclusivegateway1" targetRef="servicetask1">      <conditionExpression xsi:type="tFormalExpression"><![CDATA[${type == 1}]]></conditionExpression>    </sequenceFlow>    <serviceTask id="servicetask3" name="Service Task3" activiti:expression="${resumeService.showTask3()}"></serviceTask>    <sequenceFlow id="flow3" sourceRef="exclusivegateway1" targetRef="servicetask3">      <conditionExpression xsi:type="tFormalExpression"><![CDATA[${type == 3}]]></conditionExpression>    </sequenceFlow>    <serviceTask id="servicetask2" name="Service Task2" activiti:expression="${resumeService.showTask2()}"></serviceTask>    <sequenceFlow id="flow4" sourceRef="exclusivegateway1" targetRef="servicetask2">      <conditionExpression xsi:type="tFormalExpression"><![CDATA[${type == 2}]]></conditionExpression>    </sequenceFlow>    <endEvent id="endevent1" name="End"></endEvent>    <sequenceFlow id="flow5" sourceRef="servicetask2" targetRef="endevent1"></sequenceFlow>    <sequenceFlow id="flow6" sourceRef="servicetask1" targetRef="endevent1"></sequenceFlow>    <sequenceFlow id="flow7" sourceRef="servicetask3" targetRef="endevent1"></sequenceFlow>  </process>  <bpmndi:BPMNDiagram id="BPMNDiagram_exclusiveProcess">    <bpmndi:BPMNPlane bpmnElement="exclusiveProcess" id="BPMNPlane_exclusiveProcess">      <bpmndi:BPMNShape bpmnElement="startevent1" id="BPMNShape_startevent1">        <omgdc:Bounds height="35.0" width="35.0" x="60.0" y="140.0"></omgdc:Bounds>      </bpmndi:BPMNShape>      <bpmndi:BPMNShape bpmnElement="exclusivegateway1" id="BPMNShape_exclusivegateway1">        <omgdc:Bounds height="40.0" width="40.0" x="140.0" y="138.0"></omgdc:Bounds>      </bpmndi:BPMNShape>      <bpmndi:BPMNShape bpmnElement="servicetask1" id="BPMNShape_servicetask1">        <omgdc:Bounds height="55.0" width="105.0" x="260.0" y="40.0"></omgdc:Bounds>      </bpmndi:BPMNShape>      <bpmndi:BPMNShape bpmnElement="servicetask3" id="BPMNShape_servicetask3">        <omgdc:Bounds height="55.0" width="105.0" x="269.0" y="220.0"></omgdc:Bounds>      </bpmndi:BPMNShape>      <bpmndi:BPMNShape bpmnElement="servicetask2" id="BPMNShape_servicetask2">        <omgdc:Bounds height="55.0" width="105.0" x="260.0" y="131.0"></omgdc:Bounds>      </bpmndi:BPMNShape>      <bpmndi:BPMNShape bpmnElement="endevent1" id="BPMNShape_endevent1">        <omgdc:Bounds height="35.0" width="35.0" x="480.0" y="141.0"></omgdc:Bounds>      </bpmndi:BPMNShape>      <bpmndi:BPMNEdge bpmnElement="flow1" id="BPMNEdge_flow1">        <omgdi:waypoint x="95.0" y="157.0"></omgdi:waypoint>        <omgdi:waypoint x="140.0" y="158.0"></omgdi:waypoint>      </bpmndi:BPMNEdge>      <bpmndi:BPMNEdge bpmnElement="flow2" id="BPMNEdge_flow2">        <omgdi:waypoint x="160.0" y="138.0"></omgdi:waypoint>        <omgdi:waypoint x="160.0" y="67.0"></omgdi:waypoint>        <omgdi:waypoint x="260.0" y="67.0"></omgdi:waypoint>      </bpmndi:BPMNEdge>      <bpmndi:BPMNEdge bpmnElement="flow3" id="BPMNEdge_flow3">        <omgdi:waypoint x="160.0" y="178.0"></omgdi:waypoint>        <omgdi:waypoint x="160.0" y="247.0"></omgdi:waypoint>        <omgdi:waypoint x="269.0" y="247.0"></omgdi:waypoint>      </bpmndi:BPMNEdge>      <bpmndi:BPMNEdge bpmnElement="flow4" id="BPMNEdge_flow4">        <omgdi:waypoint x="180.0" y="158.0"></omgdi:waypoint>        <omgdi:waypoint x="260.0" y="158.0"></omgdi:waypoint>      </bpmndi:BPMNEdge>      <bpmndi:BPMNEdge bpmnElement="flow5" id="BPMNEdge_flow5">        <omgdi:waypoint x="365.0" y="158.0"></omgdi:waypoint>        <omgdi:waypoint x="480.0" y="158.0"></omgdi:waypoint>      </bpmndi:BPMNEdge>      <bpmndi:BPMNEdge bpmnElement="flow6" id="BPMNEdge_flow6">        <omgdi:waypoint x="365.0" y="67.0"></omgdi:waypoint>        <omgdi:waypoint x="497.0" y="67.0"></omgdi:waypoint>        <omgdi:waypoint x="497.0" y="141.0"></omgdi:waypoint>      </bpmndi:BPMNEdge>      <bpmndi:BPMNEdge bpmnElement="flow7" id="BPMNEdge_flow7">        <omgdi:waypoint x="374.0" y="247.0"></omgdi:waypoint>        <omgdi:waypoint x="497.0" y="247.0"></omgdi:waypoint>        <omgdi:waypoint x="497.0" y="176.0"></omgdi:waypoint>      </bpmndi:BPMNEdge>    </bpmndi:BPMNPlane>  </bpmndi:BPMNDiagram></definitions>

2、部署流程

将流程图文件放到项目当中的resources下的processes文件夹，运行程序 。

3、编写代码

新建spring boot 项目，在项目中实现一个service，并且在service中实现三个方法，代码如下：
ResumeService接口

public interface ResumeService {    void showTask1();    void showTask2();    void showTask3();}

ResumeServiceImpl实现类

@Service("resumeService")public class ResumeServiceImpl implements ResumeService {    @Override    public void showTask1() {        System.out.println("#############################执行任务1");    }    @Override    public void showTask2() {        System.out.println("#############################执行任务2");    }    @Override    public void showTask3() {        System.out.println("#############################执行任务3");    }}

利用spring boot 单元测试来实现流程：
ExclusiveProcessTest测试类

@RunWith(SpringJUnit4ClassRunner.class)@SpringBootTest(classes = SpringBootActivitiApplication.class)public class ExclusiveProcessTest {    @Autowired    RuntimeService runtimeService;    /**     * 启动流程，并给流程传入参数type，排他网关根据参数type来判断流程走向     */    @Test    public void testStartProcess() {        Map<String, Object> map = new HashMap<>();        map.put("type", 3);        runtimeService.startProcessInstanceByKey("exclusiveProcess", map);    }}

4、执行结果

运行单元测试，执行结果如下：

小知识点：排他网关中有一个属性为default，当所有条件都不满足时，排他网关默认执行default属性制定的流程。

<exclusiveGateway id="exclusivegateway1" name="Exclusive Gateway" default="flow1"></exclusiveGateway>