jbpm4.3 实现会签

jbpm4.3中会签的实现主要思路也是从网上找的。新接触jbpm简单的实现下，如果有什么疑问或错误，请指正。
jpdl.xml文件见附件，这里只贴出java代码

package com.zhangrun.custom;

import java.util.Iterator;
import java.util.List;
import java.util.Map;

import org.jbpm.api.Configuration;
import org.jbpm.api.ProcessInstance;
import org.jbpm.api.TaskService;
import org.jbpm.api.activity.ActivityExecution;
import org.jbpm.api.activity.ExternalActivityBehaviour;
import org.jbpm.api.task.Task;
import org.jbpm.pvm.internal.env.EnvironmentImpl;
import org.jbpm.pvm.internal.history.HistoryEvent;
import org.jbpm.pvm.internal.history.events.TaskActivityStart;
import org.jbpm.pvm.internal.model.Activity;
import org.jbpm.pvm.internal.model.ExecutionImpl;
import org.jbpm.pvm.internal.model.Transition;
import org.jbpm.pvm.internal.session.DbSession;
import org.jbpm.pvm.internal.task.TaskImpl;

/**
 * @author zr
 * 
 */
public class Custom implements ExternalActivityBehaviour {

	private static final long serialVersionUID = 1L;

	public void execute(ActivityExecution activityExecution) throws Exception {
		ExecutionImpl executionimpl = (ExecutionImpl) activityExecution;

		DbSession dbsession = EnvironmentImpl.getFromCurrent(DbSession.class);
		TaskImpl taskimpl = dbsession.createTask();
		taskimpl.setName("customTem");
		taskimpl.setExecution(executionimpl);
		taskimpl.setProcessInstance(executionimpl.getProcessInstance());
		taskimpl.setSignalling(false);
		taskimpl.setExecutionDbid(executionimpl.getDbid());
		dbsession.save(taskimpl);
		HistoryEvent.fire(new TaskActivityStart(taskimpl), executionimpl);
		// 子任务
		TaskImpl subtaskimpl1 = taskimpl.createSubTask();
		subtaskimpl1.setName("huigao1");
		subtaskimpl1.setAssignee("huigao1");
		subtaskimpl1.setSignalling(false);
		subtaskimpl1.setExecutionDbid(executionimpl.getDbid());
		dbsession.save(subtaskimpl1);
		HistoryEvent.fire(new TaskActivityStart(subtaskimpl1), executionimpl);
		TaskImpl subtaskimpl2 = taskimpl.createSubTask();
		subtaskimpl2.setName("huigao2");
		subtaskimpl2.setAssignee("huigao2");
		subtaskimpl2.setExecutionDbid(executionimpl.getDbid());
		subtaskimpl2.setSignalling(false);
		dbsession.save(subtaskimpl2);
		HistoryEvent.fire(new TaskActivityStart(subtaskimpl2), executionimpl);
		// 流程等待
		executionimpl.waitForSignal();
	}

	public void signal(ActivityExecution activityExecution, String signalName,
			Map<String, ?> parms) throws Exception {
		ExecutionImpl executionImpl = (ExecutionImpl) activityExecution;
		ProcessInstance pi = (ProcessInstance) executionImpl
				.getProcessInstance();
		TaskService taskService = Configuration.getProcessEngine()
				.getTaskService();
		Activity activity = executionImpl.getActivity();
		List<Task> tasks = taskService.createTaskQuery().processInstanceId(
				pi.getId()).list();

		List<Task> subTask_list = taskService.getSubTasks(tasks.get(0).getId());
		Iterator<Task> iter = subTask_list.iterator();
		while (iter.hasNext()) {
			Task subtask = iter.next();
			if (parms.get("username").equals(subtask.getAssignee())) {
				taskService.completeTask(subtask.getId());
			}
		}
		if (subTask_list == null || subTask_list.size() == 1) {
			Transition transition = null;
			if ((signalName == null)
					|| ((Task.STATE_COMPLETED.equals(signalName))
							&& (activity.getOutgoingTransitions() != null) && (activity
							.getOutgoingTransitions().size() == 1))) {
				transition = activity.getOutgoingTransitions().get(0);
			} else {
				transition = activity.findOutgoingTransition(signalName);
			}
			taskService.completeTask(tasks.get(0).getId());
			executionImpl.take(transition);
		} else {
			executionImpl.waitForSignal();
		}
	}

}