JBPM3中文用户手册——第三章：教程(5)

3.5    自定义动作示例

动作（action）是一种机制，它将你自定义的Java代码绑定到jbpm流程中去。动作能够与持有它的节点相关联（如果它们在流程的图形表示中相应地关联），或者也可以被置于事件中，如选择一个迁移、离开或进入一个节点。对于后一种情形，动作不作为图形表示的一部分，但会在流程执行的过程中于事件触发时执行。

 

我们先看一个动作实现：MyActionHandler，它在下面的例子中会用到。这个动作处理器实现的确没有做什么惊天动地的事。。。它只是设置的布尔变量isExecuted为true。这个变量是静态的，因此即可以在动作处理器内部访问，在可以直接通过动作类访问来验证它的值。

 

更多关于动作的信息，参见10.5 动作。

 

// MyActionHandler represents a class that could execute // some user code during the execution of a jBPM process. public class MyActionHandler implements ActionHandler {     // Before each test (in the setUp), the isExecuted member   // will be set to false.   public static boolean isExecuted = false;      // The action will set the isExecuted to true so the   // unit test will be able to show when the action   // is being executed.   public void execute(ExecutionContext executionContext) {     isExecuted = true;   } }

 

就像前面提到的，在测试前，我们设置了静态字段MyActionHandler.isExecuted为false：

// Each test will start with setting the static isExecuted   // member of MyActionHandler to false.   public void setUp() {     MyActionHandler.isExecuted = false;   }

 

我们将在一个迁移上启动这个动作：

public void testTransitionAction() {     // The next process is a variant of the hello world process.     // We have added an action on the transition from state 's'     // to the end-state.  The purpose of this test is to show     // how easy it is to integrate java code in a jBPM process.     ProcessDefinition processDefinition = ProcessDefinition.parseXmlString(       "<process-definition>" +       "  <start-state>" +       "    <transition to='s' />" +       "  </start-state>" +       "  <state name='s'>" +       "    <transition to='end'>" +       "      <action class='org.jbpm.tutorial.action.MyActionHandler' />" +       "    </transition>" +       "  </state>" +       "  <end-state name='end' />" +       "</process-definition>"     );         // Let's start a new execution for the process definition.     ProcessInstance processInstance =       new ProcessInstance(processDefinition);         // The next signal will cause the execution to leave the start     // state and enter the state 's'     processInstance.signal();       // Here we show that MyActionHandler was not yet executed.     assertFalse(MyActionHandler.isExecuted);     // ... and that the main path of execution is positioned in     // the state 's'     assertSame(processDefinition.getNode("s"),                processInstance.getRootToken().getNode());         // The next signal will trigger the execution of the root     // token.  The token will take the transition with the     // action and the action will be executed during the      // call to the signal method.     processInstance.signal();         // Here we can see that MyActionHandler was executed during     // the call to the signal method.     assertTrue(MyActionHandler.isExecuted);   }

 

下面这个例子，使用了相同的动作，但现在是分别放在了“进入节点”和“离开节点”事件上。注意，与只有一种事件类型的迁移相比，节点的事件类型有多种，因此在节点上事件动作，需要放到一个事件元素中去。

ProcessDefinition processDefinition = ProcessDefinition.parseXmlString(   "<process-definition>" +   "  <start-state>" +   "    <transition to='s' />" +   "  </start-state>" +   "  <state name='s'>" +   "    <event type='node-enter'>" +   "      <action class='org.jbpm.tutorial.action.MyActionHandler' />" +   "    </event>" +   "    <event type='node-leave'>" +   "      <action class='org.jbpm.tutorial.action.MyActionHandler' />" +   "    </event>" +   "    <transition to='end'/>" +   "  </state>" +   "  <end-state name='end' />" +   "</process-definition>" );   ProcessInstance processInstance =   new ProcessInstance(processDefinition);   assertFalse(MyActionHandler.isExecuted); // The next signal will cause the execution to leave the start // state and enter the state 's'.  So the state 's' is entered // and hence the action is executed. processInstance.signal(); assertTrue(MyActionHandler.isExecuted);   // Let's reset the MyActionHandler.isExecuted  MyActionHandler.isExecuted = false;   // The next signal will trigger execution to leave the  // state 's'.  So the action will be executed again. processInstance.signal(); // Voila.  assertTrue(MyActionHandler.isExecuted);