[Flowable6.4.1]DMN报错Error parsing '#{input1 == >19 }': syntax error at position 13, encountered '>'

2019-04-09 09:46:08.063 [main] ERROR org.flowable.dmn.engine.impl.RuleEngineExecutorImpl -
Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
				decision table execution failed
	at java.util.ArrayList.rangeCheck(ArrayList.java:653)
	at java.util.ArrayList.get(ArrayList.java:429)
org.flowable.common.engine.api.FlowableException: Error parsing '#{input1 ==  >19 }': syntax error at position 13, encountered '>', expected <IDENTIFIER>|<STRING>|<FLOAT>|<INTEGER>|'true'|'false'|'null'|'-'|'!'|'not'|'empty'|'('
	at com.asiainfo.cloud.service.FirstDmn.main(FirstDmn.java:38)
	at org.flowable.dmn.engine.impl.RuleEngineExecutorImpl.executeRule(RuleEngineExecutorImpl.java:237)
	at org.flowable.dmn.engine.impl.RuleEngineExecutorImpl.evaluateDecisionTable(RuleEngineExecutorImpl.java:153)
	at org.flowable.dmn.engine.impl.RuleEngineExecutorImpl.execute(RuleEngineExecutorImpl.java:94)
	at org.flowable.dmn.engine.impl.cmd.ExecuteDecisionCmd.execute(ExecuteDecisionCmd.java:63)
	at org.flowable.dmn.engine.impl.cmd.ExecuteDecisionCmd.execute(ExecuteDecisionCmd.java:31)
	at org.flowable.common.engine.impl.interceptor.DefaultCommandInvoker.execute(DefaultCommandInvoker.java:22)
	at org.flowable.common.engine.impl.interceptor.TransactionContextInterceptor.execute(TransactionContextInterceptor.java:53)
	at org.flowable.common.engine.impl.interceptor.CommandContextInterceptor.execute(CommandContextInterceptor.java:71)
	at org.flowable.common.engine.impl.interceptor.LogInterceptor.execute(LogInterceptor.java:30)
	at org.flowable.common.engine.impl.cfg.CommandExecutorImpl.execute(CommandExecutorImpl.java:56)
	at org.flowable.common.engine.impl.cfg.CommandExecutorImpl.execute(CommandExecutorImpl.java:51)
	at org.flowable.dmn.engine.impl.DmnRuleServiceImpl.executeDecisionByKey(DmnRuleServiceImpl.java:40)
	at com.asiainfo.cloud.service.FirstDmn.main(FirstDmn.java:37)
Caused by: org.flowable.common.engine.impl.de.odysseus.el.tree.TreeBuilderException: Error parsing '#{input1 ==  >19 }': syntax error at position 13, encountered '>', expected <IDENTIFIER>|<STRING>|<FLOAT>|<INTEGER>|'true'|'false'|'null'|'-'|'!'|'not'|'empty'|'('
	at org.flowable.common.engine.impl.de.odysseus.el.tree.impl.Builder.build(Builder.java:110)
	at org.flowable.common.engine.impl.de.odysseus.el.tree.TreeStore.get(TreeStore.java:61)
	at org.flowable.common.engine.impl.de.odysseus.el.TreeValueExpression.<init>(TreeValueExpression.java:70)
	at org.flowable.common.engine.impl.de.odysseus.el.ExpressionFactoryImpl.createValueExpression(ExpressionFactoryImpl.java:444)
	at org.flowable.common.engine.impl.de.odysseus.el.ExpressionFactoryImpl.createValueExpression(ExpressionFactoryImpl.java:77)
	at org.flowable.common.engine.impl.el.DefaultExpressionManager.createExpression(DefaultExpressionManager.java:88)
	at org.flowable.dmn.engine.impl.el.ELExpressionExecutor.executeInputExpression(ELExpressionExecutor.java:52)
	at org.flowable.dmn.engine.impl.RuleEngineExecutorImpl.executeInputExpressionEvaluation(RuleEngineExecutorImpl.java:259)
	at org.flowable.dmn.engine.impl.RuleEngineExecutorImpl.executeRule(RuleEngineExecutorImpl.java:219)
	... 12 common frames omitted

解决： 看org.flowable.dmn.engine.impl.el.ELInputEntryExpressionPreParser.java

    protected static String[] OPERATORS = new String[]{"==", "!=", "<", ">", ">=", "<="};
    protected static String parseSegmentWithOperator(String expression) {
        String parsedExpressionSegment;
        if (expression.length() < 2 || !StringUtils.startsWithAny(expression, OPERATORS)) {
            parsedExpressionSegment = " == " + expression;
        } else {
            parsedExpressionSegment = " " + expression;
        }

        return parsedExpressionSegment;
    }

activiti6的：

    public static String parse(String expression, String inputVariable) {

        String parsedExpression = inputVariable;
        if (expression.startsWith(".")) {
            parsedExpression += expression;
        } else {
            parsedExpression += " " + expression;
        }
        return parsedExpression;
    }

不能以空格开头，必须>这些符号。感觉是bug，应该加trim()。

注：activiti6.0.0的MvelExpressionExecutor对应的是（改为了）flowable6.4.1的ELExpressionExecutor MvelConditionExpressionPreParser对应ELInputEntryExpressionPreParser，因此activiti6不会报错。

来源：oschina

链接：https://my.oschina.net/u/2464371/blog/3036822