工作流Activiti的学习总结（五） activiti的API和虚拟工作流测试
activiti的API
???? 在activiti引擎中，你可以通过多种方式获取ProcessEngine对象，从ProcessEngine中获取各种服务对象，从而访问工作流/BPM方法。ProcessEngine和她的各种服务均为线程安全性服务。在整个项目中每一种服务仅需要保持一个引用。
ProcessEngine processEngine = ProcessEngines.getDefaultProcessEngine();
?
RuntimeService runtimeService = processEngine.getRuntimeService();
RepositoryService repositoryService = processEngine.getRepositoryService();
TaskService taskService = processEngine.getTaskService();
ManagementService managementService = processEngine.getManagementService();
IdentityService identityService = processEngine.getIdentityService();
HistoryService historyService = processEngine.getHistoryService();
FormService formService = processEngine.getFormService();
针对ProcessEngine的说明：
???? ??ProcessEngine.getDefaultProcessEngine()在第一个被调用的时候初始化并创建一个流程引擎，在以后的调用中返回同一个引用的流程引擎对象。针对流程引擎中初始化方法为ProcessEngine.init().销毁方法的方法为ProcessEngine.destroy().
ProcessEngineConfiguration.createProcessEngineConfigurationFromInputStream(inputStream).buildProcessEngine()创建工作流引擎，ProcessEngine见扫描所有的activiti.cfg.xml文件和activiti-context.xml文件。
异常策略：
??? 在activiti中org.activiti.engine.ActivitiException类为所有异常的基类。ActivitiException为非检查性异常。例如：
??? ??? **
??? ??? * Called when the task is successfully executed.
??? ??? * @param taskId the id of the task to complete, cannot be null.
??? ??? * @throws ActivitiException when no task exists with the given id.
??? ??? */
?? ??? void complete(String taskId);
其他异常类如下：
ActivitiWrongDbException:
???? Thrown when the Activiti engine discovers a mismatch between the database schema version and the engine version(schema版本和引擎版本不匹配报的错误).
ActivitiClassLoadingException:
?Thrown when an class requested to load was not found or when error occurred while loading it (eg. JavaDelegates, TaskListeners, ...).
Activiti 的测试：
????? activiti的测试支持Junit3和Junit4的单元测试。在junit3的单元测试中，org.activit.engine.test.ActivitiTestCase必须被继承。在setup（）方法中，流程引擎要初始化加载classpath下默认的activi.cfg.xml资源文件。针对不同的配置文件可能需要重新getConfigurationResource()方法。在ActivitiTestCase中可以使用org.activiti.engine.test.Deployment注解方法。
??? ??? public class MyBusinessProcessTest extends ActivitiTestCase {
??? ???????
??? ??? ??@Deployment
??? ??? ??public void testSimpleProcess() {
??? ??? ????runtimeService.startProcessInstanceByKey("simpleProcess");
??? ??? ?????
??? ??? ????Task task = taskService.createTaskQuery().singleResult();
??? ??? ????assertEquals("My Task", task.getName());
??? ??? ?????
??? ??? ????taskService.complete(task.getId());
??? ??? ????assertEquals(0, runtimeService.createProcessInstanceQuery().count());
??? ??? ??}
??? ??? }??????
在junit4中org.activiti.engine.test.ActivitiRule Rule被采用。通过ActivitiRule中getter方法获取相关的服务。在Junit4同样功能的单元测试如下：
public class MyBusinessProcessTest { @Rule public ActivitiRule activitiRule = new ActivitiRule(); @Test @Deployment public void ruleUsageExample() { RuntimeService runtimeService = activitiRule.getRuntimeService(); runtimeService.startProcessInstanceByKey("ruleUsage"); TaskService taskService = activitiRule.getTaskService(); Task task = taskService.createTaskQuery().singleResult(); assertEquals("My Task", task.getName()); taskService.complete(task.getId()); assertEquals(0, runtimeService.createProcessInstanceQuery().count()); } }
?
?
?
?
在web环境中流程引擎的使用：
??? 由于processEngine是一个线程安全性的对象可以容易在多个线程中被共享。在web容器启动加载创建工作流引擎，在容器销毁销毁工作流引擎。可以ServletContextListener实现相关的功能。
??? ??? public class ProcessEnginesServletContextListener implements ServletContextListener {
??? ??? ???
??? ??? ??public void contextInitialized(ServletContextEvent servletContextEvent) {
??? ??? ????ProcessEngines.init();
??? ??? ??}
??? ??? ?
??? ??? ??public void contextDestroyed(ServletContextEvent servletContextEvent) {
??? ??? ????ProcessEngines.destroy();
??? ??? ??}
??? ??? ?
??? ??? }
Activiti提供模拟流程的API
??
PvmProcessDefinition processDefinition = new ProcessDefinitionBuilder() .createActivity("a") .initial() .behavior(new WaitState()) .transition("b") .endActivity() .createActivity("b") .behavior(new WaitState()) .transition("c") .endActivity() .createActivity("c") .behavior(new WaitState()) .endActivity() .buildProcessDefinition(); PvmProcessInstance processInstance = processDefinition.createProcessInstance(); processInstance.start(); PvmExecution activityInstance = processInstance.findExecution("a"); assertNotNull(activityInstance); activityInstance.signal(null, null); activityInstance = processInstance.findExecution("b"); assertNotNull(activityInstance); activityInstance.signal(null, null); activityInstance = processInstance.findExecution("c"); assertNotNull(activityInstance);
?????
?
?activiti中表达式
activiti使用UEL(Unified Expression Lanuage)标记解析配置文件中表达式。UEL是EE6特性。
activiti中Expressions支持两种方式：
1.Value expression:在activiti中DelegateExecution是在上下文中是使用“execution”在表达式上下文被使用的。所有在使用值表达式是，所有变量和spring的beans使用execution将被隐藏，在表达式将不被执行。使用方法如下：
${myVar}?? ${myBean.myProperty}
2.Method expression:使用方法访问的方式。常用方式如下：
${printer.print()}? ${myBean.addNewOrder(“orerName”)}?
?备注：在activiti中expression支持解析的类型为原始类型，beans，lists,arrays和maps