How to joint strings in JUEL?

[kafeitu]

I want to joint some strings for a variable that set by listener.

${execution.setVariable('message', 'reject reason: max value for ' + category)}
‍‍‍

In this example, the type of 'reject reason: max value for' is text, the category is a variable. The value should be rejrect reason: max value for AAAA  if value  is 'AAAA' of category.

Trace:

org.activiti.engine.ActivitiException: Error while evaluating expression: ${execution.setVariable('message', 'reject reason: max value for ' + category)}
   at org.activiti.engine.impl.el.JuelExpression.getValue(JuelExpression.java:59)
   at org.activiti.engine.impl.bpmn.listener.ExpressionExecutionListener.notify(ExpressionExecutionListener.java:35)
   at org.activiti.engine.impl.pvm.runtime.AtomicOperationTransitionNotifyListenerTake.execute(AtomicOperationTransitionNotifyListenerTake.java:47)
   at org.activiti.engine.impl.interceptor.CommandContext.performOperation(CommandContext.java:85)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperationSync(ExecutionEntity.java:535)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperation(ExecutionEntity.java:530)
   at org.activiti.engine.impl.pvm.runtime.AtomicOperationTransitionDestroyScope.execute(AtomicOperationTransitionDestroyScope.java:115)
   at org.activiti.engine.impl.interceptor.CommandContext.performOperation(CommandContext.java:85)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperationSync(ExecutionEntity.java:535)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperation(ExecutionEntity.java:530)
   at org.activiti.engine.impl.pvm.runtime.AtomicOperationTransitionNotifyListenerEnd.eventNotificationsCompleted(AtomicOperationTransitionNotifyListenerEnd.java:36)
   at org.activiti.engine.impl.pvm.runtime.AbstractEventAtomicOperation.execute(AbstractEventAtomicOperation.java:56)
   at org.activiti.engine.impl.interceptor.CommandContext.performOperation(CommandContext.java:85)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperationSync(ExecutionEntity.java:535)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperation(ExecutionEntity.java:530)
   at org.activiti.engine.impl.pvm.runtime.AbstractEventAtomicOperation.execute(AbstractEventAtomicOperation.java:49)
   at org.activiti.engine.impl.interceptor.CommandContext.performOperation(CommandContext.java:85)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperationSync(ExecutionEntity.java:535)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperation(ExecutionEntity.java:530)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.take(ExecutionEntity.java:370)
   at org.activiti.engine.impl.bpmn.behavior.ExclusiveGatewayActivityBehavior.leave(ExclusiveGatewayActivityBehavior.java:74)
   at org.activiti.engine.impl.bpmn.behavior.FlowNodeActivityBehavior.execute(FlowNodeActivityBehavior.java:36)
   at org.activiti.engine.impl.pvm.runtime.AtomicOperationActivityExecute.execute(AtomicOperationActivityExecute.java:44)
   at org.activiti.engine.impl.interceptor.CommandContext.performOperation(CommandContext.java:85)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperationSync(ExecutionEntity.java:535)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperation(ExecutionEntity.java:530)
   at org.activiti.engine.impl.pvm.runtime.AtomicOperationTransitionNotifyListenerStart.eventNotificationsCompleted(AtomicOperationTransitionNotifyListenerStart.java:52)
   at org.activiti.engine.impl.pvm.runtime.AbstractEventAtomicOperation.execute(AbstractEventAtomicOperation.java:56)
   at org.activiti.engine.impl.interceptor.CommandContext.performOperation(CommandContext.java:85)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperationSync(ExecutionEntity.java:535)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperation(ExecutionEntity.java:530)
   at org.activiti.engine.impl.pvm.runtime.AbstractEventAtomicOperation.execute(AbstractEventAtomicOperation.java:49)
   at org.activiti.engine.impl.interceptor.CommandContext.performOperation(CommandContext.java:85)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperationSync(ExecutionEntity.java:535)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperation(ExecutionEntity.java:530)
   at org.activiti.engine.impl.pvm.runtime.AtomicOperationTransitionCreateScope.execute(AtomicOperationTransitionCreateScope.java:49)
   at org.activiti.engine.impl.interceptor.CommandContext.performOperation(CommandContext.java:85)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperationSync(ExecutionEntity.java:535)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperation(ExecutionEntity.java:530)
   at org.activiti.engine.impl.pvm.runtime.AtomicOperationTransitionNotifyListenerTake.execute(AtomicOperationTransitionNotifyListenerTake.java:65)
   at org.activiti.engine.impl.interceptor.CommandContext.performOperation(CommandContext.java:85)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperationSync(ExecutionEntity.java:535)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperation(ExecutionEntity.java:530)
   at org.activiti.engine.impl.pvm.runtime.AtomicOperationTransitionDestroyScope.execute(AtomicOperationTransitionDestroyScope.java:115)
   at org.activiti.engine.impl.interceptor.CommandContext.performOperation(CommandContext.java:85)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperationSync(ExecutionEntity.java:535)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperation(ExecutionEntity.java:530)
   at org.activiti.engine.impl.pvm.runtime.AtomicOperationTransitionNotifyListenerEnd.eventNotificationsCompleted(AtomicOperationTransitionNotifyListenerEnd.java:36)
   at org.activiti.engine.impl.pvm.runtime.AbstractEventAtomicOperation.execute(AbstractEventAtomicOperation.java:56)
   at org.activiti.engine.impl.interceptor.CommandContext.performOperation(CommandContext.java:85)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperationSync(ExecutionEntity.java:535)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperation(ExecutionEntity.java:530)
   at org.activiti.engine.impl.pvm.runtime.AbstractEventAtomicOperation.execute(AbstractEventAtomicOperation.java:49)
   at org.activiti.engine.impl.interceptor.CommandContext.performOperation(CommandContext.java:85)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperationSync(ExecutionEntity.java:535)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperation(ExecutionEntity.java:530)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.take(ExecutionEntity.java:370)
   at org.activiti.engine.impl.bpmn.behavior.BpmnActivityBehavior.performOutgoingBehavior(BpmnActivityBehavior.java:102)
   at org.activiti.engine.impl.bpmn.behavior.BpmnActivityBehavior.performDefaultOutgoingBehavior(BpmnActivityBehavior.java:51)
   at org.activiti.engine.impl.bpmn.behavior.FlowNodeActivityBehavior.leave(FlowNodeActivityBehavior.java:44)
   at org.activiti.engine.impl.bpmn.behavior.AbstractBpmnActivityBehavior.leave(AbstractBpmnActivityBehavior.java:47)
   at org.activiti.engine.impl.bpmn.behavior.UserTaskActivityBehavior.signal(UserTaskActivityBehavior.java:98)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.signal(ExecutionEntity.java:353)
   at org.activiti.engine.impl.persistence.entity.TaskEntity.complete(TaskEntity.java:157)
   at org.activiti.engine.impl.cmd.SubmitTaskFormCmd.execute(SubmitTaskFormCmd.java:47)
   at org.activiti.engine.impl.cmd.NeedsActiveTaskCmd.execute(NeedsActiveTaskCmd.java:58)
   at org.activiti.engine.impl.interceptor.CommandExecutorImpl.execute(CommandExecutorImpl.java:24)
   at org.activiti.engine.impl.interceptor.CommandContextInterceptor.execute(CommandContextInterceptor.java:60)
   at org.activiti.spring.SpringTransactionInterceptor$1.doInTransaction(SpringTransactionInterceptor.java:42)
   at org.springframework.transaction.support.TransactionTemplate.execute(TransactionTemplate.java:130)
   at org.activiti.spring.SpringTransactionInterceptor.execute(SpringTransactionInterceptor.java:40)
   at org.activiti.engine.impl.interceptor.LogInterceptor.execute(LogInterceptor.java:32)
   at org.activiti.engine.impl.FormServiceImpl.submitTaskFormData(FormServiceImpl.java:70)
   at me.kafeitu.activiti.chapter10.PurchaseEventSubProcessTest.testRejectOnTreasurer(PurchaseEventSubProcessTest.java:69)
   at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
   at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
   at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
   at java.lang.reflect.Method.invoke(Method.java:597)
   at junit.framework.TestCase.runTest(TestCase.java:168)
   at org.activiti.engine.impl.test.PvmTestCase.runTest(PvmTestCase.java:85)
   at junit.framework.TestCase.runBare(TestCase.java:134)
   at org.activiti.engine.impl.test.AbstractActivitiTestCase.runBare(AbstractActivitiTestCase.java:99)
   at org.activiti.spring.impl.test.SpringActivitiTestCase.runBare(SpringActivitiTestCase.java:51)
   at junit.framework.TestResult$1.protect(TestResult.java:110)
   at junit.framework.TestResult.runProtected(TestResult.java:128)
   at junit.framework.TestResult.run(TestResult.java:113)
   at junit.framework.TestCase.run(TestCase.java:124)
   at junit.framework.TestSuite.runTest(TestSuite.java:243)
   at junit.framework.TestSuite.run(TestSuite.java:238)
   at org.junit.internal.runners.JUnit38ClassRunner.run(JUnit38ClassRunner.java:83)
   at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
   at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
   at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
   at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
   at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
   at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)
Caused by: org.activiti.engine.impl.javax.el.ELException: Cannot coerce 'reject reason: max value for ' to class java.lang.Double
   at org.activiti.engine.impl.juel.TypeConverterImpl.coerceToDouble(TypeConverterImpl.java:126)
   at org.activiti.engine.impl.juel.TypeConverterImpl.coerceToType(TypeConverterImpl.java:315)
   at org.activiti.engine.impl.juel.TypeConverterImpl.convert(TypeConverterImpl.java:365)
   at org.activiti.engine.impl.juel.Bindings.convert(Bindings.java:137)
   at org.activiti.engine.impl.juel.NumberOperations.add(NumberOperations.java:74)
   at org.activiti.engine.impl.juel.AstBinary$1.apply(AstBinary.java:33)
   at org.activiti.engine.impl.juel.AstBinary$SimpleOperator.eval(AstBinary.java:27)
   at org.activiti.engine.impl.juel.AstBinary.eval(AstBinary.java:106)
   at org.activiti.engine.impl.juel.AstParameters.eval(AstParameters.java:34)
   at org.activiti.engine.impl.juel.AstMethod.invoke(AstMethod.java:88)
   at org.activiti.engine.impl.juel.AstMethod.eval(AstMethod.java:75)
   at org.activiti.engine.impl.juel.AstEval.eval(AstEval.java:50)
   at org.activiti.engine.impl.juel.AstNode.getValue(AstNode.java:26)
   at org.activiti.engine.impl.juel.TreeValueExpression.getValue(TreeValueExpression.java:114)
   at org.activiti.engine.impl.delegate.ExpressionGetInvocation.invoke(ExpressionGetInvocation.java:33)
   at org.activiti.engine.impl.delegate.DelegateInvocation.proceed(DelegateInvocation.java:37)
   at org.activiti.engine.impl.delegate.DefaultDelegateInterceptor.handleInvocation(DefaultDelegateInterceptor.java:25)
   at org.activiti.engine.impl.el.JuelExpression.getValue(JuelExpression.java:50)
   … 95 more
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[ronald_van_kuij]

http://www.lmgtfy.com/?q=juel%20concatenate%20string