[#0x002D] variable的name和mapped-name

最新推荐文章于 2021-02-16 19:48:49 发布

原创最新推荐文章于 2021-02-16 19:48:49 发布 · 162 阅读

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本文探讨了流程中变量的作用域问题，特别是name和mapped-name的区别。通过案例分析，解释了ContextInstance和TaskInstance如何创建和访问变量，以及不同类型的变量对其作用域的影响。

　　看似是一个variable有name和mapped-name两个名称，其实情况很复杂。看例子。

　　假定我们有一个极其简单的流程vartest (surprisingly it also means V-Artest, but i must say that i'm not a Laker fan) 。在start-state的controller里添加一个variable，name为"var"，mapped-name为"variable"，如下：

<?xml version="1.0" encoding="UTF-8"?>

<process-definition  xmlns=""  name="vartest">

	<start-state name="start-state1">
		<task>
			<controller>
				<variable access="read,write" name="var" mapped-name="variable"></variable>
			</controller>
		</task>
		<transition to="task-node1"></transition>
	</start-state>

	<task-node name="task-node1"		
		<transition to="end-state1"></transition>
	</task-node>

	<end-state name="end-state1"></end-state>

</process-definition>

　　然后我们来写一个Test Case：

public class AccessVariable extends TestCase
{
	public void testPayProcess() throws Exception
	{
		JbpmContext jc = JbpmConfiguration.getInstance().
				createJbpmContext();
		
		ProcessDefinition pd = jc.getGraphSession().
				findLatestProcessDefinition("vartest");
		ProcessInstance pi = pd.createProcessInstance();
		ContextInstance ci = pi.getContextInstance();
		TaskInstance ti = pi.getTaskMgmtInstance().createStartTaskInstance()
		
		//hint 1:
		//ci can create new variable (not declared in <controller>)
		//and ti can access the variable ci created
		ci.setVariable("abc", "ABC");
		System.out.println(ti.getVariable("abc")); //ABC
		ti.setVariable("abc", "CBA");
		System.out.println(ci.getVariable("abc")); //CBA
	
		//hint 1:	
		//also, ti can create this kind of variables
		//and ci can access the variable ti created
		ti.setVariable("def", "DEF");
		System.out.println(ci.getVariable("def")); //DEF	
		ci.setVariable("def", "FED");
		System.out.println(ti.getVariable("def")); //FED
		
		//hint 2:		
		//for the variables declared in <controller>, it's the same situation
		//both ci and ti can create and access this kind of variable
		ci.setVariable("var", "VAR");
		System.out.println(ti.getVariable("var")); //VAR
		ti.setVariable("var", "RAV");
		System.out.println(ci.getVariable("var")); //RAV

		//hint 3:	
		//"var" doesn't affect "variable"
		System.out.println(ti.getVariable("variable")); //null
		System.out.println(ci.getVariable("variable")); //null

		//hint 4:	
		//things becaome a little different when using mapped-name
		ti.setVariable("variable", "VARIABLE");
		System.out.println(ti.getVariable("variable")); //VARIABLE
		System.out.println(ci.getVariable("variable")); //null
	
		//hint 4:	
		//it's clear that ti and ci both holds an "variable", respectively
		ci.setVariable("variable", "ELBAIRAV");
		System.out.println(ti.getVariable("variable")); //VARIABLE
		System.out.println(ci.getVariable("variable")); //ELBAIRAV

		//hint 3:	
		//and "variable" doesn't affect "var"
		System.out.println(ti.getVariable("var")); //RAV
		System.out.println(ci.getVariable("var")); //RAV
			
		ti.end();
		pi.end();
		jc.close();
	}
}

输出结果如注释所示。

　　可以看出，除了mapped-name之外，ti和ci可以随意SetVariable(key, value)，SetVariable的过程包含了create的过程，key可以是name，也可以是其他字符串，且这种类型的变量(名称为name或是任意字符串，只要不是mapped-name)ti和ci可以随意访问，这类变量对ti和ci的作用域是一样的(类似于全局变量)。

　　但name和mapped-name变量没有任何关系，如hint 3所示，"var"的值不会影响"variable"，反过来"variable"的值也不会影响"var"。

　　且mapped-name变量对ti和ci来说更像是2个变量，其作用域严格区分，没有任何交集，如hint 4所示。