Activiti 自定义事件监听和邮件通知

参照Activiti官方文档https://www.activiti.org/userguide/#eventDispatcher

首先，建立我们的需求。即当有任务创建、分配、完成时，邮件通知对应用户。

完成步骤如下：

1. Activiti为我们提供了事件监听接口– ActivitiEventListener

2. org.activiti.engine.delegate.event.ActivitiEventType提供了各种可以监听到的事件类型

3. 通过对应事件，获取有关联的用户，任务名称等。

public class OwnEventListener implements ActivitiEventListener {    @Override    public void onEvent(ActivitiEvent event) {        System.out.println("Event received: " + event.getType());        if (event.getType() == ActivitiEventType.TASK_CREATED                || event.getType() == ActivitiEventType.TASK_ASSIGNED                || event.getType() == ActivitiEventType.TASK_COMPLETED) {            ActivitiEntityEvent entityEvent = (ActivitiEntityEvent) event;            TaskEntity taskEntity = (TaskEntity) entityEvent.getEntity();            MailWrapper.getInstance().sendTaskMail(taskEntity.getOwner(), taskEntity.getAssignee(), taskEntity.getName(), event.getType());        }    }

最重要的一步就是强制将ActivitiEvent转换为其sub-interface(ActivitiEntityEvent)，再将获取的Entity强制转换为具体的Entity，最终获取相应信息。

在邮件发送模块，需要构建邮件模版，单例化邮件组件。

public class MailWrapper {    private final Logger log = LoggerFactory.getLogger(MailWrapper.class);    @Autowired    private MailSender mailSender;    private MailWrapper() {    Velocity.init(PropertiesUtil.readPropertiesInEnv("vm.properties"));    }    private static class WrapperSingleton {        static final MailWrapper mv = new MailWrapper();    }    public static MailWrapper getInstance() {        return WrapperSingleton.mv;    }    public void sendTaskMail(String owner, String assignee, String taskName, ActivitiEventType eventType) {        SimpleMailMessage msg = new SimpleMailMessage();        String toEmailAddress = KeystoneClient.getInstance().findEmailByUserId(assignee);        String ownerName = KeystoneClient.getInstance().findNameByUserId(owner);        String assigneeName = KeystoneClient.getInstance().findNameByUserId(assignee);        TaskMail tMail = new TaskMail(ownerName, assigneeName, taskName, eventType);        VelocityContext model = new VelocityContext();        model.put("task", tMail);        Template template = Velocity.getTemplate("template/task_email.vm", "utf8");        StringWriter w = new StringWriter();        template.merge(model, w);        msg.setSubject("hello world");        msg.setTo(toEmailAddress);        msg.setText(w.toString());        try {            mailSender.send(msg);            log.info("mail has been sent to " + toEmailAddress);        } catch (MailException e) {            System.err.println(e.getMessage());        }    }}

在构建模版时，使用的是org.apache.velocity组件，其资源配置文件如下：

resource.loader = classclass.resource.loader.description = Velocity Classpath Resource Loaderclass.resource.loader.class = org.apache.velocity.runtime.resource.loader.ClasspathResourceLoader

告诉velocity，加载我们定义的模版文件时，使用classloader资源路径。当然，也可以配置物理路径，具体请参照官网，这里不加赘述。