Drools中的“无法找到课程"错误 [英] `Unable to find class` error in Drools

问题描述

我正在尝试在Drools中定义一个非常简单的函数，如下所示:

I'm trying to define a very simple function in Drools as below:

import java.util.List;

function int sumLengths(List<String> strings) {
    int counter = 0;
    for (String s : strings)
        counter += s.length();
    return counter;
}

但它给了我错误:

Exception in thread "main" java.lang.RuntimeException: [ function sumLengths (line:5):
Unable to resolve type List<String> while building function. java.lang.ClassNotFoundException: Unable to find class 'List<String>' ]

有什么主意吗?

推荐答案

也许这是泛型的问题(

Perhaps it is an issue with generics (This points me to that conclusion). Have you tried the following (or similar):

function int sumLengths(List strings) {
    int counter = 0;
    for (Object s : strings)
        counter += ((String) s).length();
    return counter;
}

如果它不起作用，您可以改用它:

If it doesn't work you could use this instead:

function int sumLengths(String[] strings) {
    int counter = 0;
    int length = (strings != null) ? strings.length : -1;
    for (int idx = 0; idx < length; ++idx) {
        counter += strings[idx].length();
    }
    return counter;
}

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