Problems with Dependencies Exception in thread "main" java.lang.NoClassDefFoundError: org/kie/api/KieServices$Factory with Drools version 7.59.0

Question

我刚开始学习 Drools，但使用起来并不顺利，我正在尝试一个简单的项目，但出现此错误。

Exception in thread "main" java.lang.NoClassDefFoundError: org/kie/api/KieServices$Factory at com.sample.App.main(App.java:12)

Whosebug 和其他讨论的所有建议都没有帮助。有没有人有办法解决吗？当我使用 mvn clean install 是 BUILD SUCCESS

这是我的代码

com.sample.App

package com.sample;

import com.model.Item;
import org.kie.api.KieServices;
import org.kie.api.runtime.KieContainer;
import org.kie.api.runtime.KieSession;

public class App {
    public static void main(String[] args)
    {
        System.out.println("Rule engine");
        KieServices ks = KieServices.Factory.get();
        KieContainer kContainer = ks.getKieClasspathContainer();
        KieSession kSession = kContainer.newKieSession();

        Item item = new Item("A", (float) 123.35);
        System.out.println("Item category: " + item.getCategory());
        kSession.insert(item);
        int fired = kSession.fireAllRules();
        System.out.println("Number of Rules executed: " + fired);
        System.out.println("Item Category: " + item.getCategory());
    }
}

com.sample.model

package com.model;

public class Item {
    private String category;
    private Float cost;

    public Item(String category, Float cost) {
        this.category = category;
        this.cost = cost;
    }

    public String getCategory() {
        return category;
    }

    public void setCategory(String category) {
        this.category = category;
    }

    public Float getCost() {
        return cost;
    }

    public void setCost(Float cost) {
        this.cost = cost;
    }
}

这是我的pom

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>org.example</groupId>
    <artifactId>DroolCmonDude2</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <maven.compiler.source>11</maven.compiler.source>
        <maven.compiler.target>11</maven.compiler.target>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.kie</groupId>
            <artifactId>kie-api</artifactId>
            <version>7.59.0.Final</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>org.drools</groupId>
            <artifactId>drools-core</artifactId>
            <version>7.59.0.Final</version>
        </dependency>
        <dependency>
            <groupId>org.drools</groupId>
            <artifactId>drools-compiler</artifactId>
            <version>7.59.0.Final</version>
        </dependency>
        <dependency>
            <groupId>org.drools</groupId>
            <artifactId>drools-decisiontables</artifactId>
            <version>7.59.0.Final</version>
        </dependency>
    </dependencies>

</project>

我的 Rules.drl 在 resources.rules

package resources.rules;

import com.model.Item;

rule "Classify Item - Low Range"
    when
        $i: Item(cost < 200)
    then
        $i.setCategory(Category.LOW_RANGE);
end

我的kmodule.xml

<kmodule xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xmlns="http://jboss.org/kie/6.0.0/kmodule">
</kmodule>

解决方案

正如@RoddyoftheFrozenPeas 指出的那样，解决方案是添加 drools-mvel、drools-model-compiler 和 sfj4 的依赖项并起作用。这是给 Drools 7> 这是我的 pom 现在的样子：

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>org.example</groupId>
    <artifactId>DroolsAnotherChance</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <maven.compiler.source>11</maven.compiler.source>
        <maven.compiler.target>11</maven.compiler.target>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.drools</groupId>
            <artifactId>drools-core</artifactId>
            <version>7.59.0.Final</version>
        </dependency>
        <dependency>
            <groupId>org.drools</groupId>
            <artifactId>drools-compiler</artifactId>
            <version>7.59.0.Final</version>
        </dependency>
        <dependency>
            <groupId>org.drools</groupId>
            <artifactId>drools-decisiontables</artifactId>
            <version>7.59.0.Final</version>
        </dependency>
        <dependency>
            <groupId>org.drools</groupId>
            <artifactId>drools-mvel</artifactId>
            <version>7.59.0.Final</version>
        </dependency>
        <dependency>
            <groupId>org.drools</groupId>
            <artifactId>drools-model-compiler</artifactId>
            <version>7.59.0.Final</version>
        </dependency>
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-api</artifactId>
            <version>1.7.25</version>
        </dependency>

        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-nop</artifactId>
            <version>1.7.25</version>
        </dependency>
    </dependencies>

</project>

Answer 1

7.45 中引入的 Drools 库有一个非向后兼容的更改。您可以在文档的发行说明 here.

中阅读相关内容

基本上，从 7.45 开始，“可执行模型”的引入导致 mvel 支持被分解为一个单独的模块。因此，您现在需要包含以下依赖项之一：

• drools-mvel-编译器
• drools-模型编译器

您需要哪一个取决于您实际在做什么。在 7.45 之前，mvel 编译器支持是 drools-compiler 依赖项的一部分，因此不需要这种额外的依赖项。

（请注意，您不需要 kie-api 依赖项。）