Drools Rule Template错误[错误：未封闭的@if {}块使用占位符时预期的@end {}]

编程问答 2022-07-09

问题描述

如果子类集合列表中使用了占位符，则

drools规则模板无法编译。

我有这个简单的类结构

public class Parent {
   private List<Child> children;
}
public class Child {
   private String gender;
}

使用占位符@ {gender}时，ExternalSpreadsheetCompiler引发错误 [错误：未封闭的@if {}块。预期的@end {}] 

Parent($children: children)
Child(gender == "@{gender}") from $children

在模板中对“ MALE”进行硬编码时没有问题

Parent($children: children)
Child(gender == "MALE") from $children

有什么主意吗？感谢您的帮助。

完整错误堆栈跟踪：

[Line: 42,Column: 0]
    at org.drools.core.runtime.rule.impl.DefaultConsequenceExceptionHandler.handleException(DefaultConsequenceExceptionHandler.java:39)
    at org.drools.core.common.DefaultAgenda.handleException(DefaultAgenda.java:1291)
    at org.drools.core.phreak.RuleExecutor.innerFireActivation(RuleExecutor.java:442)
    at org.drools.core.phreak.RuleExecutor.fireActivation(RuleExecutor.java:380)
    at org.drools.core.phreak.RuleExecutor.fire(RuleExecutor.java:136)
    at org.drools.core.phreak.RuleExecutor.evaluateNetworkAndFire(RuleExecutor.java:89)
    at org.drools.core.concurrent.AbstractRuleEvaluator.internalEvaluateAndFire(AbstractRuleEvaluator.java:33)
    at org.drools.core.concurrent.SequentialRuleEvaluator.evaluateAndFire(SequentialRuleEvaluator.java:43)
    at org.drools.core.common.DefaultAgenda.fireLoop(DefaultAgenda.java:1101)
    at org.drools.core.common.DefaultAgenda.internalFireAllRules(DefaultAgenda.java:1048)
    at org.drools.core.common.DefaultAgenda.fireAllRules(DefaultAgenda.java:1040)
    at org.drools.core.impl.StatefulKNowledgeSessionImpl.internalFireAllRules(StatefulKNowledgeSessionImpl.java:1341)
    at org.drools.core.impl.StatefulKNowledgeSessionImpl.fireAllRules(StatefulKNowledgeSessionImpl.java:1332)
    at org.drools.core.impl.StatefulKNowledgeSessionImpl.fireAllRules(StatefulKNowledgeSessionImpl.java:1316)
    at org.drools.template.parser.TemplateDataListener.finishSheet(TemplateDataListener.java:158)
    at org.drools.decisiontable.parser.xls.ExcelParser.finishSheet(ExcelParser.java:277)
    at org.drools.decisiontable.parser.xls.ExcelParser.processSheet(ExcelParser.java:212)
    at org.drools.decisiontable.parser.xls.ExcelParser.parseWorkbook(ExcelParser.java:105)
    at org.drools.decisiontable.parser.xls.ExcelParser.parseFile(ExcelParser.java:84)
    at org.drools.decisiontable.ExternalSpreadsheetCompiler.compile(ExternalSpreadsheetCompiler.java:140)
    at org.drools.decisiontable.ExternalSpreadsheetCompiler.compile(ExternalSpreadsheetCompiler.java:168)
    at org.drools.decisiontable.ExternalSpreadsheetCompiler.compile(ExternalSpreadsheetCompiler.java:99)
    at org.drools.decisiontable.ExternalSpreadsheetCompiler.compile(ExternalSpreadsheetCompiler.java:85)
    at com.dhl.gssdemo.config.SpringDroolsConfig.addTemplateContent(SpringDroolsConfig.java:112)
    at com.dhl.gssdemo.config.SpringDroolsConfig.classpathDrlKieBase(SpringDroolsConfig.java:102)
    at com.dhl.gssdemo.config.SpringDroolsConfig$$EnhancerBySpringcglib$$583d8208.cglib$classpathDrlKieBase$0(<generated>)
    at com.dhl.gssdemo.config.SpringDroolsConfig$$EnhancerBySpringcglib$$583d8208$$FastClassBySpringcglib$$25a5fef6.invoke(<generated>)
    at org.springframework.cglib.proxy.MethodProxy.invokeSuper(MethodProxy.java:244)
    at org.springframework.context.annotation.ConfigurationClassEnhancer$BeanMethodInterceptor.intercept(ConfigurationClassEnhancer.java:331)
    at com.dhl.gssdemo.config.SpringDroolsConfig$$EnhancerBySpringcglib$$583d8208.classpathDrlKieBase(<generated>)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:154)
    ... 52 common frames omitted
Caused by: java.lang.RuntimeException: [Error: unclosed @if{} block. expected @end{}]

解决方法

我遇到了同样的问题，我认为它与解决 MVEL 表达式有关，但我通过使用以下解决方法（使用 $$ 而不是 $）解决了它

例如你的情况

Parent($children: 孩子) Child(gender == "@{gender}") 来自 $$children

droolsdroolsredhat-decision-manager