java.lang.RuntimeException: unable to invoke method: xxx.xxx.XXX.getXXX: target of method is null in BPMS

Issue

• After several hours, the application would start throwing "target of method is null" error

org.jbpm.workflow.instance.WorkflowRuntimeException: [com.sample.bpmn.hello:2 - :2] -- Exception when trying to evaluate constraint  in split 
    at org.jbpm.workflow.instance.node.SplitInstance.internalTrigger(SplitInstance.java:67)
    at org.jbpm.workflow.instance.impl.NodeInstanceImpl.trigger(NodeInstanceImpl.java:155)
    at org.jbpm.workflow.instance.impl.NodeInstanceImpl.triggerNodeInstance(NodeInstanceImpl.java:337)
    at org.jbpm.workflow.instance.impl.NodeInstanceImpl.triggerCompleted(NodeInstanceImpl.java:296)
    at org.jbpm.workflow.instance.node.StartNodeInstance.triggerCompleted(StartNodeInstance.java:66)
    at org.jbpm.workflow.instance.node.StartNodeInstance.internalTrigger(StartNodeInstance.java:43)
    at org.jbpm.workflow.instance.impl.NodeInstanceImpl.trigger(NodeInstanceImpl.java:155)
    at org.jbpm.ruleflow.instance.RuleFlowProcessInstance.internalStart(RuleFlowProcessInstance.java:35)
    at org.jbpm.process.instance.impl.ProcessInstanceImpl.start(ProcessInstanceImpl.java:226)
    at org.jbpm.workflow.instance.impl.WorkflowProcessInstanceImpl.start(WorkflowProcessInstanceImpl.java:362)
    at org.jbpm.process.instance.ProcessRuntimeImpl.startProcessInstance(ProcessRuntimeImpl.java:194)
    at org.jbpm.process.instance.ProcessRuntimeImpl.startProcess(ProcessRuntimeImpl.java:176)
    at org.jbpm.process.instance.ProcessRuntimeImpl.startProcess(ProcessRuntimeImpl.java:168)
    at org.drools.core.common.AbstractWorkingMemory.startProcess(AbstractWorkingMemory.java:1575)
    at org.drools.core.impl.StatefulKnowledgeSessionImpl.startProcess(StatefulKnowledgeSessionImpl.java:366)
...
Caused by: java.lang.RuntimeException: Exception when trying to evaluate constraint  in split 
    at org.jbpm.workflow.instance.node.SplitInstance.executeStrategy(SplitInstance.java:93)
    at org.jbpm.workflow.instance.node.SplitInstance.internalTrigger(SplitInstance.java:63)
    ... 43 more
Caused by: java.lang.RuntimeException: unable to execute ReturnValueEvaluator: 
    at org.jbpm.process.instance.impl.ReturnValueConstraintEvaluator.evaluate(ReturnValueConstraintEvaluator.java:131)
    at org.jbpm.workflow.instance.node.SplitInstance.executeStrategy(SplitInstance.java:86)
    ... 44 more
Caused by: java.lang.RuntimeException: unable to invoke method: com.sample.MyPojo.getName: target of method is null
    at org.mvel2.optimizers.impl.refl.nodes.GetterAccessor.getValue(GetterAccessor.java:66)
    at org.mvel2.optimizers.impl.refl.nodes.VariableAccessor.getValue(VariableAccessor.java:37)
    at org.mvel2.ast.ASTNode.getReducedValueAccelerated(ASTNode.java:108)
    at org.mvel2.ast.BinaryOperation.getReducedValueAccelerated(BinaryOperation.java:114)
    at org.mvel2.MVELRuntime.execute(MVELRuntime.java:86)
    at org.mvel2.compiler.CompiledExpression.getDirectValue(CompiledExpression.java:123)
    at org.mvel2.compiler.CompiledExpression.getValue(CompiledExpression.java:119)
    at org.mvel2.MVEL.executeExpression(MVEL.java:930)
    at org.drools.core.util.MVELSafeHelper$RawMVELEvaluator.executeExpression(MVELSafeHelper.java:481)
    at org.jbpm.process.instance.impl.MVELReturnValueEvaluator.evaluate(MVELReturnValueEvaluator.java:114)
    at org.jbpm.process.instance.impl.ReturnValueConstraintEvaluator.evaluate(ReturnValueConstraintEvaluator.java:129)
    ... 45 more
Caused by: java.lang.NullPointerException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    at org.mvel2.optimizers.impl.refl.nodes.GetterAccessor.getValue(GetterAccessor.java:43)
    ... 55 more