写一个简单的工作流（二）

    hoho，今天完成了选择路由的实现，完成了配置文件的读写和解析，流程定义文件还是决定采用xml文件，不过与其他工作流引擎采用的xml完全不同，因为是基于petri网的，因此引入了place的概念，比如下面这个4个节点的顺序路由的流程：

< workflow  maxCases ="100" >
     < node  type ="start"  name ="start"  id ="0" >
         < inputs >
             < place  id ="1"   />
         </ inputs >
         < outputs >
             < place  id ="2"   />
         </ outputs >
     </ node >
     < node  name ="hello"  id ="1"  resource ="user" >
         < conditions  type ="and" >
             < condition
                 class ="net.rubyeye.insect.workflow.impl.NullHandler"  value ="false"
                variable-name ="name"   />
         </ conditions >
         < handler
             class ="net.rubyeye.insect.workflow.test.HelloWorldHandler"   />
         < inputs >
             < place  id ="2"   />
         </ inputs >
         < outputs >
             < place  id ="3"   />
         </ outputs >
     </ node >
     < node  name ="calc"  id ="2"  resource ="user" >
         < conditions  type ="and" >
             < condition  variable-name ="num" >
                 < exp >
                     <![CDATA[ num<=1000 ]]>
                 </ exp >
             </ condition >
             < conditions  type ="or" >
                 < condition  variable-name ="num" >
                     < exp >
                         <![CDATA[ num>=10 ]]>
                     </ exp >
                 </ condition >
                 < condition
                     class ="net.rubyeye.insect.workflow.impl.NullHandler"  value ="false"
                    variable-name ="name"   />
             </ conditions >
         </ conditions >
         < handler
             class ="net.rubyeye.insect.workflow.test.CalculateHandler"   />
         < inputs >
             < place  id ="3"   />
         </ inputs >
         < outputs >
             < place  id ="4"   />
         </ outputs >
     </ node >
     < node  type ="end"  name ="hello"  id ="3" >
         < inputs >
             < place  id ="4"   />
         </ inputs >
         < outputs >
             < place  id ="5"   />
         </ outputs >
     </ node >
</ workflow >

   
并行路由和选择路由引入了and-split,and-join,or-split,or-join四种transition，比如and-split，它就有多个输出place：

< node  name ="split"  type ="and-split"  id ="1"  resource ="user" >
         < inputs >
             < place  id ="2"   />
         </ inputs >
         < outputs >
             < place  id ="3"   />
             < place  id ="4"   />
         </ outputs >
     </ node >

   Place和Transition都有条件，用于决定操作是否执行，Transition额外指定了驱动的资源以及回调的handler，这一点非常重要，资源可能是用户、用户组、某个时间点定时事件、特定消息等等。
   今天额外发现的一个好处就是，引入Place之后，我可以轻易地将不同的流程连接起来组织成一个更复杂的流程，仅仅是需要修改各个流程的开始和结束的节点的输入输出库所,从而实现了层次化的Petri网,，类似代码：

WorkFlow sequence  =  wm.getWorkFlow( " sequence " );
        WorkFlow concurrency  =  wm.getWorkFlow( " concurrency " );
        WorkFlow choose  =  wm.getWorkFlow( " choose " );

         // 组合流程
        composite  =   new  WorkFlow();
        composite.setName( " composite " );
        composite.setId( 100 );
        
        wm.saveWorkFlow(composite);

         // 修改开始结束节点的输入输出库所
        sequence.getEnd().setType(TransitionType.NORMAL);
        sequence.getEnd().setOutputs(concurrency.getStart().getInputs());

        concurrency.getEnd().setType(TransitionType.NORMAL);
        concurrency.getEnd().setOutputs(choose.getStart().getInputs());
        
        composite.setStart(sequence.getStart());
        composite.setEnd(choose.getEnd());
        List < Transition >  transitions  =   new  ArrayList < Transition > ();
        transitions.addAll(sequence.getTransitions());
        transitions.addAll(concurrency.getTransitions());
        transitions.addAll(choose.getTransitions());
        composite.setTransitions(transitions);