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踩1踩OSWorkflow和jBMP:39行代码实现一个很好很强大的工作流引擎

2012-12-20 
踩一踩OSWorkflow和jBMP:39行代码实现一个很好很强大的工作流引擎?现成的工作流引擎有很多,我以前曾浅尝过

踩一踩OSWorkflow和jBMP:39行代码实现一个很好很强大的工作流引擎

踩1踩OSWorkflow和jBMP:39行代码实现一个很好很强大的工作流引擎

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现成的工作流引擎有很多,我以前曾浅尝过OSWorkflow和jBPM,但都未能深入研究。总感觉它们过于复杂,术语也特别多,让我对它们逐渐失去了兴趣(还有那些流程设计器,个人觉得完全没有存在的必要:1.一般的用户用不来;2.程序员直接写代码(流程定义代码量一般几十行就够了),要流程设计器干嘛?)。另外有一个开源的基于Grails的工作流项目:http://www.grailsflow.org/,尽管它宣称“GrailsFlow: Your Workflow just got easier!”,我感觉它还是做得太复杂,凭我多年的IT从业经验,竟然没看懂,我也不想继续把时间浪费在它上面。

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工作流引擎,从本质上说,是状态机,只要控制好了各个状态之间的转换就行了。我使用Groovy/Grails有一段时间了,感觉Grails的webflow设计得不错,简单易懂,很好很强大,只可惜它只适合做在线支付之类的流程。但是webflow却给了我一些启发,尤其是它那优美的DSL方式的流程定义,让我印象深刻。利用Groovy的BuilderSupport,Closure,还有我已经整合到Grails中的db4o持久化框架,很容易快速写出一个工作流引擎。

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我也用一把DSL,一个流程定义的例子如下:

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   start {       on('Submit') {o->           println o.state           // change o.state to a new state ...       }    }   state1 {       on('Action11') {o->           // do something with o and then change o.state to a new state ...       }   }   state2 {       on('Action21') {o->           // do something with o and then change o.state to a new state ...       }       on('Action22') {o->           // do something with o and then change o.state to a new state ...                  }   }
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怎么样,够简洁吧?

在某个状态下,请求某个操作后,要执行的具体动作在对应的closure中写好了。这些closures中的代码犹如诸葛亮的锦囊妙计,工作流引擎依计行事。

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现在设想我们把DSL写在workflows目录下的demo.groovy(扩展名随便你怎么写)中,怎样使工作流引擎读懂这个流程呢?这需要一点点Groovy Builder的知识,自己看Groovy官方文档或Google。

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我们的FlowBuilder长得像这个样子:

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class FlowBuilder extends BuilderSupport {    private Map flow = [:]    private String _state    protected void setParent(Object parent, Object child){}    protected Object createNode(Object name){        createNode(name, null)    }    protected Object createNode(Object name, Object value){        createNode(name, null, value)    }    protected Object createNode(Object name, Map attributes){        createNode(name, attributes, null)    }    protected Object createNode(Object name, Map attributes, Object value){}    protected void nodeCompleted(Object parent, Object node) {}    def invokeMethod(String name, args) {          switch(name) {            case 'flow':                super.invokeMethod name, args                break                case 'on':                flow[_state][args[0]] = args[1]                break            default:                _state = _state ? name : 'start' // the first state is always 'start'                flow[_state] = flow[_state] ?: [:]                super.invokeMethod name, args                break        }    }}
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简单测试一下:

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def builder = new FlowBuilder()def s = '{->'+'''   // DSL可从文件中读取   start {       on('Submit') {o->           println o.state           // change o.state to a new state ...       }    }   state1 {       on('Action11') {o->           // do something with o and then change o.state to a new state ...       }   }   state2 {       on('Action21') {o->           // do something with o and then change o.state to a new state ...       }       on('Action22') {o->           // do something with o and then change o.state to a new state ...                  }   }'''+'}'this.class.classLoader.rootLoader.addURL( new URL("file:///E:/lib/bsf-2.4.0.jar") )def closure = new org.apache.bsf.BSFManager().eval("groovy", null, 0, 0, s)builder.flow closureprintln builder.flow

输出以下内容:?

[start:[submit:_$_run_closure1_closure2_closure5@31f2a7], state1:[action11:_$_run_closure1_closure3_closure6@131c89c], state2:[action21:_$_run_closure1_closure4_closure7@1697b67, action22:_$_run_closure1_closure4_closure8@24c4a3]]

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这表明,流程定义已经被成功地装入一Map中。

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其实,代码可以写得更精简:直接在文件中写成Map的形式(这可以看作另一种形式的DSL),以下是文章开头的图片所对应的工作流流程定义:

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[    start : [        'Save as Draft' : {o, p, m->        o.state = 'draft'            o.principals = [m]        }, Submit : {o, p, m->        o.state = 'assign'        o.principals = [p.principal]        }    ]    , draft : [        Save : {o, p, m->        o.state = 'draft'            o.principals = [o.originator]        }, Submit : {o, p, m->        o.state = 'assign'        o.principals = [p.principal]        }    ]    , assign : [        Submit : {o, p, m->            o.state = 'working'        }    ]    , working : [        Ask : {o, p, m->            o.state = 'has_questions'            o.principals = [o.originator]        }        , Submit : {o, p, m->            o.state = 'report_ready'            o.principals = [o.originator]        }    ]    , has_questions : [        Answer : {o, p, m->            o.state = 'working'            o.principals = [o.previousPrincipal]        }    ]    , report_ready : [        OK : {o, p, m->            o.state = 'end'            o.principals = [o.originator]        }        , NG : {o, p, m->            o.state = 'working'            o.principals = [o.previousPrincipal]        }    ]        , _ds : [        report_type : {            return [['sas','SAS report'], ['cogonos','Cogonos report']]            }, principal : {        def principals = []    User.findAll(sort:'username').each {    principals << [it.username, it.profile?.name ?: it.username]    }        principals        }    ]]

?这样连FlowBuilder也省了,一行eval代码就解析并载入了流程定义。。。

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以上内容还没涉及到我的工作流引擎,其实有了groovy语言的closure的强大支持,实现这个引擎实在是小菜一碟:

class WorkflowService {    static transactional = true    def formServicedef process(params) {    def params_values = JSON.parse(params.values)        def workflowBean = WorkflowBean.find(id:params_values._bid)        def workflow        if(workflowBean) {            workflow = getWorkflow(workflowBean)        } else {            def workflowDef = WorkflowDefinition.find(id:params_values._fid)            if(workflowDef) {            workflow = getWorkflow(workflowDef)                workflowBean = new WorkflowBean(state:'start', definition:workflowDef)            }        }    def state = workflowBean.statedef action = workflow."$state"?."${params_values._action}"if(action && action instanceof Closure) {action.call(workflowBean, params_values, params.session.user.username)workflowBean.save()notifyPrincipals(workflowBean)return [ok:true]}        def arrayStore = [:]        workflow?._ds?.each {        arrayStore[it.key] = it.value.call()        }    def values = [_fid:workflowBean?.definition?.id, _bid:workflowBean?.id, _state:workflowBean?.state]    workflowBean?.data?.each {    values[it.key] = it.value    }        [workflowBean:workflowBean,          form:formService.getFlowForm(workflowBean, params.servletContext), values:values as JSON,         arrayStore:arrayStore as JSON,         _actions:workflow?."${workflowBean?.state}"?.keySet() as JSON]    }}

只有39行代码 -- 不能望39K女项背,我只能做个39L男 :-)?

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1 楼 tedeyang 2012-08-09   准备怎么实现split\join ?
怎么实现condition?
怎么实现trigger?

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