JBPM 7.52动态编译GDST时Kie Builder无法解析ObjectType问题求解

问题背景 #

使用JBPM Business Central Workbench 7.52版本，动态编译GDST规则表时，Kie Builder无法识别自定义数据对象，报错Unable to resolve ObjectType 'message' : [Rule name='Row 1 MsgRules']。

相关代码与资源 #

自定义数据对象代码

package com.stackoverflow.question1;
/** This class was automatically generated by the data modeler tool. */
public class message implements java.io.Serializable {
    static final long serialVersionUID = 1L;
    private java.lang.String status;
    private java.lang.String name;
    private java.lang.String message;

    public message() {}
    public message(java.lang.String status, java.lang.String name,
            java.lang.String message) {
        this.status = status;
        this.name = name;
        this.message = message;
    }

    public java.lang.String getStatus() {
        return this.status;
    }
    public void setStatus(java.lang.String status) {
        this.status = status;
    }
    public java.lang.String getName() {
        return this.name;
    }
    public void setName(java.lang.String name) {
        this.name = name;
    }
    public java.lang.String getMessage() {
        return this.message;
    }
    public void setMessage(java.lang.String message) {
        this.message = message;
    }
}

GDST规则表对应生成的DRL代码

package com.stackoverflow.question1;

//from row number: 1
//Name was null
rule "Row 1 MsgRules"
    dialect "mvel"
    when
        MSG : message( name == null )
    then
        modify( MSG ) {
                setMessage( "Name was null" )
        }
end

//from row number: 2
//Name was not null
rule "Row 2 MsgRules"
    dialect "mvel"
    when
        MSG : message( name != null )
    then
        modify( MSG ) {
                setMessage( "Name was not null" )
        }
end

原编译代码

public static KieContainer loadGdstIntoContainer( String gdstFileName) {
    logger.info("KieUtilities:loadKieContainer - Started");
    try {
        KieServices   kieServices   = KieServices.Factory.get();
        KieFileSystem kieFileSystem = kieServices.newKieFileSystem();
        
        //URL resource = KieUtilities.class.getClassLoader().getResource("BaseClaim.class");
        //kieFileSystem.write(ResourceFactory.newUrlResource(resource));
        
        kieFileSystem.write(ResourceFactory.newClassPathResource("MsgRules.gdst"));
        KieBuilder kieBuilder = kieServices.newKieBuilder(kieFileSystem);
        kieBuilder.buildAll();
        if (kieBuilder.getResults().hasMessages(Message.Level.ERROR)) {
            throw new RuntimeException("Build Errors:\n" + kieBuilder.getResults().toString());
        }
        KieRepository kieRepository = kieServices.getRepository();
        KieContainer kieContainer = kieServices.newKieContainer(kieRepository.getDefaultReleaseId());
        logger.info("KieUtilities:loadKieContainer - Finished");
        return kieContainer;
    }
    catch(Exception ex) {
        logger.info("KieUtilities:loadKieContainer - Failed");
        logger.info(ex.getLocalizedMessage());
        throw ex;
    }
}

之前尝试的无效修复

URL resource = KieUtilities.class.getClassLoader().getResource("message.class");
kieFileSystem.write(ResourceFactory.newUrlResource(resource));

修复方案 #

错误原因 #

之前的修复无效有两个核心问题：

1. KieBuilder编译规则时需要目标类在指定的类加载路径中，直接将.class文件写入KieFileSystem根路径，不符合Kie的资源路径规范，无法被识别
2. 类文件没有按照包结构存放，com.stackoverflow.question1.message对应的路径应该是com/stackoverflow/question1/message.class，直接放根路径找不到对应类。

三种可行修复方式，按实现难度从低到高排序： #

方式一：指定KieBuilder使用当前上下文类加载器（最便捷）

只要你的message类已经在当前项目的类路径中，不需要额外写入类文件到KieFileSystem，只需要在创建KieBuilder时传入当前线程的上下文类加载器即可，修改代码如下：

// 将原来创建KieBuilder的代码替换为下面这行
KieBuilder kieBuilder = kieServices.newKieBuilder(kieFileSystem, Thread.currentThread().getContextClassLoader());

方式二：将数据对象Java源文件写入KieFileSystem一起编译

如果需要完全从零构建，不依赖当前类路径的类，可以把message.java源文件按包路径写入KieFileSystem，让KieBuilder先编译Java类再编译规则：

// 写入Java源文件，注意路径对应包结构
kieFileSystem.write("src/main/java/com/stackoverflow/question1/message.java",
    ResourceFactory.newClassPathResource("message.java"));
// 再写入GDST规则文件
kieFileSystem.write(ResourceFactory.newClassPathResource("MsgRules.gdst"));

方式三：修正class文件写入路径

如果你一定要使用已经编译好的.class文件，修改写入时的路径即可：

URL resource = KieUtilities.class.getClassLoader().getResource("com/stackoverflow/question1/message.class");
kieFileSystem.write("classes/com/stackoverflow/question1/message.class",
    ResourceFactory.newUrlResource(resource));

内容的提问来源于stack exchange，提问作者vscoder