Apache属性描述符的dynamicallyModifiesClasspath()世界程序

Question

我有一个处理器，它依赖于某个jar作为依赖项。但是，对依赖jar的更改非常频繁。因此，我希望能够将jar路径指定为处理器的属性，并让nifi在每次修改属性中的路径并重新启动处理器时加载jar。正如在dynamicallyModifiesClasspath中所解释的那样，使用这篇文章应该是可行的。然而，我无法做到这一点。下面是我使用dynamicallyModifiesClasspath属性编写的hello程序代码：

(下面，Djl代表“动态jar加载”，这是一个随机前缀，我猜是用来命名这个hello world程序的。)

DjlDependencyClass.java

这是我的nifi处理器所依赖的类，我希望在我的nifi处理器中动态地更改它的jar路径。

public class DjlDependencyClass {

    public static String getMessage()
    {
        return "DJL-DEPENDENCY VERSION-1";
    }
}

MyDjlProcessor.java

这是nifi处理器，它依赖于DjlDependencyClass。

import org.apache.nifi.annotation.lifecycle.OnScheduled;
import org.apache.nifi.components.PropertyDescriptor;
import org.apache.nifi.processor.exception.ProcessException;    
import org.apache.nifi.processor.AbstractProcessor;
import org.apache.nifi.processor.ProcessContext;
import org.apache.nifi.processor.ProcessSession;
import org.apache.nifi.processor.ProcessorInitializationContext;
import org.apache.nifi.processor.Relationship;
import org.apache.nifi.processor.util.StandardValidators;

import com.mycompany.djldependency.DjlDependencyClass;

import java.util.ArrayList;
import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

public class MyDjlProcessor extends AbstractProcessor {

    public static final Relationship MY_RELATIONSHIP = new Relationship.Builder()
            .name("MY_RELATIONSHIP")
            .description("Example relationship")
            .build();

    public static final PropertyDescriptor pathToDjlDependencyJar = new PropertyDescriptor.Builder()
            .name("Djl Dependency JAR")
            .description("Djl Dependency JAR")
            .required(true)
            .addValidator(StandardValidators.NON_EMPTY_VALIDATOR)
            .dynamicallyModifiesClasspath(true)
            .expressionLanguageSupported(true)
            .build();

    private List<PropertyDescriptor> descriptors;

    private Set<Relationship> relationships;

    @Override
    protected void init(final ProcessorInitializationContext context) {
        final List<PropertyDescriptor> descriptors = new ArrayList<PropertyDescriptor>();
        descriptors.add(pathToDjlDependencyJar);
        this.descriptors = Collections.unmodifiableList(descriptors);

        final Set<Relationship> relationships = new HashSet<Relationship>();
        relationships.add(MY_RELATIONSHIP);
        this.relationships = Collections.unmodifiableSet(relationships);
    }

    @Override
    public Set<Relationship> getRelationships() {
        return this.relationships;
    }

    @Override
    public final List<PropertyDescriptor> getSupportedPropertyDescriptors() {
        return descriptors;
    }

    @OnScheduled
    public void onScheduled(final ProcessContext context) {

    }

    @Override
    public void onTrigger(final ProcessContext context, final ProcessSession session) throws ProcessException {
        System.out.println(DjlDependencyClass.getMessage());
    }
}

这就是pom中的依赖项被标记为具有provided作用域的方式，这样依赖jar就不会嵌入到nar中：

   <dependency>
        <groupId>com.mycompany</groupId>
        <artifactId>djl-dependency</artifactId>
        <version>0.0.1-SNAPSHOT</version>
        <scope>provided </scope>
    </dependency>

我正在测试这个处理器如下：

​

​

处理器的配置：

​

​

我得到以下例外：

2019-05-27 17:01:54,536 ERROR [Timer-Driven Process Thread-1] com.mycompany.djl.MyDjlProcessor MyDjlProcessor[id=f8fa5750-016a-1000-ecc3-c19732119332] MyDjlProcessor[id=f8fa5750-016a-1000-ecc3-c19732119332] failed to process due to java.lang.NoClassDefFoundError: com/mycompany/djldependency/DjlDependencyClass; rolling back session: {}
java.lang.NoClassDefFoundError: com/mycompany/djldependency/DjlDependencyClass
    at com.mycompany.djl.MyDjlProcessor.onTrigger(MyDjlProcessor.java:76)
    at org.apache.nifi.processor.AbstractProcessor.onTrigger(AbstractProcessor.java:27)
    at org.apache.nifi.controller.StandardProcessorNode.onTrigger(StandardProcessorNode.java:1122)
    at org.apache.nifi.controller.tasks.ContinuallyRunProcessorTask.call(ContinuallyRunProcessorTask.java:147)
    at org.apache.nifi.controller.tasks.ContinuallyRunProcessorTask.call(ContinuallyRunProcessorTask.java:47)
    at org.apache.nifi.controller.scheduling.TimerDrivenSchedulingAgent$1.run(TimerDrivenSchedulingAgent.java:128)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
    at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308)
    at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:180)
    at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:294)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at java.lang.Thread.run(Thread.java:748)

我在这里做傻事吗？

请下载两个项目(nifi和dependency ) 这里。

Answer 1

PropertyDescriptor的API文档提到了以下注意事项：

如果组件包含将PropertyDescriptor设置为true的dynamicallyModifiesClasspath，则还必须用@RequiresInstanceClassloading对组件进行注释，否则组件将被视为无效。

我不确定这个“无效”部分是否仍然有效，但是是的，在更新了处理器代码，并使用@RequiresInstanceClassloading对其进行注释之后，我能够让它正常工作。