JBPM3 DAO层的设计

jbpm3 本身提供很多API，可直接操作实体，包结构是以对象去规划的。假设对jbpm进行扩展，继承任务实例、增加其它实体，那么就少不了对于实体的新增、删除和修改；数据要返回给应用（J2EE），需要定义Interface、DAO、DTO等等。以前的项目并没有去区分这一块，对于实例的操作没有使用DAO，而是定义一个类和所需的方法，然后传入JbpmContext或Session 如：

public class WorkflowUtil {
	public List<ProcessInstance> findProcessInstancesByProcessDefinition(JbpmContext jbpmContext, String accountName) {
		Session session = jbpmContext.getSession();
		String ql = "SELECT processInstance\n"
			+ "FROM org.jbpm.graph.exe.ProcessInstance processInstance\n"
			+ "WHERE processInstance.processDefinition = :processDefinition\n"
			+ "AND processInstance.end IS NULL\n";
		session.createQuery(ql);
		Query query = session.createQuery(ql).setParameter("processDefinition", processDefinition);
		return query.list();
}

其实使用Interface有很多好处，所以定义DAO层；每个方法中都有一个JbpmContext/Session,不够优雅，所以简化参数。如

public class WorkflowDaoBean implements WorkflowDao {

	private Session session;
	
	private final static Log log = LogFactory.getLog(WorkflowDaoBean.class);
	
	@SuppressWarnings("deprecation")
	public WorkflowDaoBean(){
		JbpmContext currentJbpmContext = JbpmContext.getCurrentJbpmContext();
	    if (currentJbpmContext!=null) {
	    	session = currentJbpmContext.getSession();
	    } else {
	    	log.info("无法获取当前JbpmContext。");
	    }
	}
	
	public WorkflowDaoBean(Session session){
		this.session = session;
	}
	
	@SuppressWarnings("unchecked")
	public List<ProcessInstance> findProcessInstancesByProcessDefinition(ProcessDefinition processDefinition) {
		String ql = "SELECT processInstance\n"
			+ "FROM org.jbpm.graph.exe.ProcessInstance processInstance\n"
			+ "WHERE processInstance.processDefinition = :processDefinition\n"
			+ "AND processInstance.end IS NULL\n";
		session.createQuery(ql);
		Query query = session.createQuery(ql).setParameter("processDefinition", processDefinition);
		return query.list();
	}