jBPM Developers Guide(jBPM开发指南)--Chapter 3. BPMN 2.0(第四部分)

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3.8.9.?Tasks(任务)

?? ?A task representswork that needs to be done by an external entity, such as a human actor or anautomated service.

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?? ?一个任务表示工作需要被外部实体完成，比如人工或自动服务。

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?? ?It's important tonote that the BPMN semantics of a 'task' differ from the JPDL semantics. InJPDL, the concept 'task' is always used in the context of a human actor doingsome type of work. When the process engine encounters a task in JPDL, it willcreate a task in some human actor's task list and it will behave as a waitstate. In BPMN 2.0 however, there are several task types, some indicating await state (eg. the?User Task?and some indicating an automaticactivity (eg. the?Service Task).So take good care not to confuse the meaning of the task concept when switchinglanguages.

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?? ?重要的是注意BPMN语法的'task'与jPDL语法的区别。在jPDL中，'task'的概念总是用在人工做一些事情的环境。jPDL流程引擎在遇到task时，它会创建一个task， 并分配一些人进行处理，然后它会进入等待状态。然而在BPMN 2.0中， 这里有很多任务类型，一些表示等待状态（比如，User Task），?一些表示自动活动（比如，Service Task）。所以在切换流程语言时要小心不要混淆了任务的概念。

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?? ?Tasks are depictedby a rounded rectangle, typically containing a text inside. The type of thetask (user task, service task, script task, etc.) is shown as a little icon onthe left top corner of the rectangle. Depending on the task type, the enginewill execute different functionality.

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?? ?任务使用一个圆角矩形表示，一般内部包含一些文字。任务的类型（用户任务，服务任务，脚本任务，等等）使用小图标进行区分，显示在矩形的左上角。 根据任务的类型，引擎会执行不同的功能。

3.8.10.?Task: User Task(任务：人工任务)

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?? ?A?User task?is the typical 'human task' that isfound in practically every workflow or BPM software out there. When processexecution reaches such a user task, a new human task is created in task listfor a given user.

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?? ?usertask是典型的'人工任务'， 几乎在每个工作流软件或BPMN软件中都可以找到。当流程执行到达一个user task时， 任务列表中就会创建一个新人工任务，并分配给给定用户进行处理。

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?? ?The main differencewith a?manual task?(which also signifies work for a humanactor) is that the task is known to the process engine. The engine can trackthe completion, assignee, time, etc which is not the case for a manual task.

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?? ?和manual task（也表示将任务分配给人进行处理）的主要区别是user task也会被流程引擎记录。 引擎可以跟踪任务完成、分配、时间等等，而manual task则不可以。

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?? ?A user task isdepicted as a rounded rectangle with a small user icon in the top left corner.

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?? ?user task描绘为一个圆角矩形，在左上角是一个小用户图标。

?? ?A user task isdefined as follows in the BPMN 2.0 XML:

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?? ?BPMN 2.0中user task XM定义如下：

<userTask id="myTask" name="My task" />

?? ?According to thespecification, multiple implementations are possible (Webservice, WS-humantask,etc.), as stated by using the?implementation?attribute. Currently, only thestandard jBPM task mechanism is available, so there is no point (yet) indefining the 'implementation' attribute.

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?? ?根据规范，user task可以采用多种实现（WebService, WS-humantask，等等），使用implementation属性来标示。 当前，只有标准的jBPM任务机制才可以用，所以这里还没有定义'implementation'属性的功能。

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?? ?The BPMN 2.0specification contains quite a few ways of assigning user tasks to user(s),group(s), role(s), etc. The current BPMN 2.0 jBPM implementation allows toassign tasks using a resourceAssignmentExpression, combinedwith the?humanPerformeror PotentialOwner?construct.It is to be expected that this area will evolve future releases.

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?? ?BPMN 2.0规范包含了一些方法把任务分配给用户、组、角色等等。当前的BPMN 2.0 jBPM实现允许使用resourceAssignmentExpression并结合humanPerformer 或 PotentialOwner结构来分配任务。这部分希望在未来的版本里能够得到进一步演化。

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?? ?A?potentialOwner?is used when you want to make acertain user, group, role, etc. a?candidate?for a certain task. Take the followingexample. Here the candidate group for the task 'My task' will be the'management' group. Also note that a resource must be defined?outside the process, such that thetask assignment can reference the resource. In fact, any activity can referenceone or more resource elements. Currently, only defining this resource is enough(since it is a required attribute by the spec), but this will be enhanced in alater release (eg. resources can have runtime parameters).

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?? ?potentialOwner用来，当你想把一个任务分配给一个候选的人， 组，角色时（这里所说的意思是当你需要分配给一个组时则系统为该组建立一个任务，并不会为该组中每个人员建立一个任务，即组里面的人员都是任务候选人）。如下面例子所示。这里的'Mytask'任务的候选人组是'management'用户组。也要注意，这是需要在流程外部定义一个资源， 这样任务分配器才可以引用到这个资源。实际上，任何活动都可以引用一个或多个资源元素。当前，只需要定义这个资源就可以了（因为它是规范中的一个必须的元素），但是在以后的发布中会进行加强（比如，资源可以拥有运行时参数）。?

<resource id="manager" name="manager" /> <process ...>...                <userTask id="myTask" name="My task">  <potentialOwner resourceRef="manager" jbpm:type="group">    <resourceAssignmentExpression>      <formalExpression>management</formalExpression>    </resourceAssignmentExpression>  </potentialOwner></userTask> 

?? ?Note that we areusing a specific extension here (jbpm:type="group"), todefine this is a group assignment. If this attribute is removed, the group semanticswill be used as default (which would be ok in this example). Now suppose thatPeter and Mary are a member of the management group (here using the defaultidentity service):

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?? ?注意，我们使用了一个特定的后缀 (jbpm:type="group")，来定义这是一个用户组的分配方式。如果删除了这个属性，就会默认使用用户组的语法（在这个例子中也是没问题的）。现在假设Peter和Mary是management组的成员(这里使用默认的身份服务)：

identityService.createGroup("management");    identityService.createUser("peter", "Peter", "Pan");identityService.createMembership("peter", "management");    identityService.createUser("mary", "Mary", "Littlelamb");identityService.createMembership("mary", "management"); 

?? ?Then both peter andmary can look in their task list for this task (code snippet from the exampleunit test):

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?? ?Peter和Mary都可以在他们的任务列表中看到这条任务 （代码来自实例单元测试）：

// Peter and Mary are both part of management, so they both should see the taskList<Task> tasks = taskService.findGroupTasks("peter");assertEquals(1, tasks.size()); tasks = taskService.findGroupTasks("mary");assertEquals(1, tasks.size());    // Mary claims the taskTask task = tasks.get(0);taskService.takeTask(task.getId(), "mary");assertNull(taskService.createTaskQuery().candidate("peter").uniqueResult());    taskService.completeTask(task.getId());assertProcessInstanceEnded(processInstance);

?? ??When the assignmentshould be done to a?candidateuser, just use the?jbpm:type="user"?attribute.

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?? ?当分配方式为候选用户时，可使用jbpm:type="user"属性。

<userTask id="myTask" name="My User task">  <potentialOwner resourceRef="employee" jbpm:type="user">    <resourceAssignmentExpression>      <formalExpression>peter</formalExpression>    </resourceAssignmentExpression>  </potentialOwner></userTask>

?? ?In this example,peter will be able to find the task since he's a candidate user for the task.

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?? ?在这个例子里，Peter可以看到任务，因为他是这个任务的候选用户。

List<Task> tasks = taskService.createTaskQuery().candidate("peter").list(); 

?? ?A?human performer?is used when you want to assign a taskdirectly to a certain user, group, role, etc. The way to do this looks verymuch like that of the potential owner.

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?? ?human performer用来，当你想把一个任务直接分配给一个确定人、组、角色时（这里需要注意当你分配给一个组时，系统将为该组中每一个人员建立一个任务，并不为该组建立任务）。这个方法的使用方式看起来和potentialowner很像。

<resource id="employee" name="employee" />      <process ...>...                 <userTask id="myTask" name="My User task">  <humanPerformer resourceRef="employee">    <resourceAssignmentExpression>      <formalExpression>mary</formalExpression>    </resourceAssignmentExpression>  </humanPerformer></userTask>

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?? ?In this example, thetask will be directly assigned to Mary. She can now find the task in her tasklist:

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?? ?在这个例子中，任务会直接分配给Mary。她可以在自己的任务列表中看到这个任务：

List<Task> tasks = taskService.findPersonalTasks("mary");

?? ?Since the taskassignment is done through the use of a?formalExpression,it's also possible to define expressions that are evaluated at runtime. Theexpressions itself need to be put inside a?${},as usual in jBPM. For example, if a process variable 'user' is defined, then itcan be used inside an expression. More complex expressions are of coursepossible.

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?? ?因为任务分配可以通过使用?formalExpression来完成，它也可以定义一个表达式中，该表达式在运行期进行解析。表达式本身需要放在?${}中，这和jBPM一样。比如，如果流程变量中定义了一个'user'变量，那么它可以用在表达式中。当然也可以使用更复杂的表达式。

<userTask id="myTask" name="My User task">  <humanPerformer resourceRef="employee">    <resourceAssignmentExpression>      <formalExpression>${user}</formalExpression>    </resourceAssignmentExpression>  </humanPerformer></userTask>

?? ?Note that it is notneeded to use the 'jbpm:type' on a humanPerformer element, since only directuser assignments can be done. If a task needs to be assigned to a role orgroup, use the potentialOwner with a group type (when you assign a task to agroup, all members of that group will always be candidate users for that group- hence the usage of potentialOwner).

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?? ?注意不需要在humanPerformer元素中使用'jbpm:type'，因为只能进行直接用户分配。如果任务需要被分配给一个角色或一个组，使用potentialOwner和group类型（当你把任务分配给一个组时， 组中的所有成员都会成为候选用户 - 参考potentialOwner的用法）。

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3.8.11.?Task: Java ServiceTask(任务：Java服务任务)

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?? ?A?Service Task?is an automatic activity that callssome sort of service, such as a web service, Java service, etc. Currently, onlyJava service invocations are supported by the jBPM engine, but Web serviceinvocations are planned for a future release.

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?? ?Service Task是一个自动活动，它会调用一系列的服务， 比如web service，java service等等。当前jBPM引擎只支持调用java service，但是web service的调用在未来的版本中已经做了计划。

?? ?Defining a servicetask requires quite a few lines of XML (the BPEL influence is certainly visiblehere). Of course, in the near future, we expect that tooling will simplify thisarea a lot. A service task is defined as follows:

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?? ?定义一个服务任务需要好几行XML（这里就可以看到BPEL的影响力）。 当然，在不久的未来，我们希望有工具可以把这部分大量的简化。一个服务任务需要如下定义：

<serviceTask id="MyServiceTask" name="My service task"   implementation="Other" operationRef="myOperation" /> 

?? ?The service task hasa required?id?and an optional?name. The?implementation?attribute is used to indicate what thetype of the invoked service is. Possible values are WebService, Other orUnspecified. Since we've only implemented the Java invocation, only the?Other?choice will do something useful forthe moment.

?? ?服务任务定义需要一个必填的id和一个可选的?name。implementation元素是用来表示调用服务的类型。可选值有WebService, Other或者Unspecified。 因为我们只实现了Java调用，所以现在只能选择Other。

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?? ?The service taskwill invoke a certain operation that is referenced by the?operationRef?attribute using the id of an?operation. Such an operation is partof an?interface?as shown below. Every operation has atleast one?inputmessage?and atmost one?outputmessage.

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?? ?服务任务将调用operationRef属性中引用operation。每个操作都是interface的一部分，定义如下所示。每个操作都至少有一个?输入信息，并且最多有一个输出信息。

<interface id="myInterface"    name="org.jbpm.MyJavaServicek">    <operation id="myOperation2" name="myMethod">      <inMessageRef>inputMessage</inMessageRef>      <outMessageRef>outputMessage</outMessageRef>    </bpmn:operation></interface> 

?? ?For a Java service,the?name of theinterface?is usedto specificy the fully qualified classname of the Java class. The?name of the operation?is then used to specify the name ofthe method that must be called. The input/output message that represent theparameters/return value of the Java method are defined as follows:

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?? ?对于java服务，接口的名称用来指定java类的全类名。操作的名称?用来指定将要调用方法名。输入/输出信息表示着java方法的参数/返回值，定义如下所示：

<message id="inputMessage" name="input message" structureRef="myItemDefinition1" />

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?? ?Several elements inBPMN are so-called 'item-aware', including this message construct. This meansthat they are involved in storing or reading items during process execution.The data structure to hold these elements is specified using a reference to an?ItemDefinition. In this context, themessage specifies its data structure by referencing an Itemdefinition in the?structureRef?attribute.

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?? ?包括这个消息结构在内，BPMN中很多元素叫做'item感知'。这意味着它们会在流程执行过程中保存或读取item。负责这些元素的数据结构需要使用ItemDefinition。在这个环境下，消息指定了它的数据结构，通过引用?structureRef属性中定义的ItemDefinition。

<itemDefinition id="myItemDefinition1" >    <jbpm:arg>      <jbpm:object expr="#{var1}" />    </jbpm:arg>  </itemDefinition>    <itemDefinition id="myItemDefinition2">    <jbpm:var name="returnVar" />  </itemDefinition> 

?? ?Do note that this isnot fully standard BPMN 2.0 as by the specification (hence the 'jbpm' prefix).In fact, according to the specification, the ItemDefinition shouldn't containmore than a data structure definition. The actual mapping between inputparamaters, with a ceratin data structure, is done in the ioSpecification?section of the serviceTask. However,the current jBPM BPMN 2.0 implementation hasn't implemented that construct yet.So, this means that the current usage as described above, will probably changein the near future.

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?? ?注意，这写的不完全是BPMN 2.0标准（因此都有'jbpm'的前缀）。实际上，根据标准，ItemDefinition不应该包含多余一个数据结构定义。对于输入参数的数据结构映射，应该在serviceTask的ioSpecification部分来定义。然而，当前jBPM BPMN 2.0实现还没有实现。所以，这意味着上面所描述的使用方法，很可能在不久的未来就会出现变化。

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?? ?Important note: Interfaces, ItemDefinitions and messagesare defined outside a <process>.?See the example?ServiceTaskTest?for a concrete process and unit test.

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?? ?重要提醒：Interface、ItemDefinitions和Message都需要定义在 <process>外边。可以参考实际流程和单元测试示例?ServiceTaskTest。

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