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https://issues.apache.org/jira/browse/METRON-777?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16118756#comment-16118756
 ] 

ASF GitHub Bot commented on METRON-777:
---------------------------------------

Github user bbende commented on a diff in the pull request:

    https://github.com/apache/metron/pull/530#discussion_r131986154
  
    --- Diff: 
bundles-lib/src/main/java/org/apache/metron/bundles/bundle/Bundle.java ---
    @@ -0,0 +1,48 @@
    +/*
    + * Licensed to the Apache Software Foundation (ASF) under one or more
    + * contributor license agreements.  See the NOTICE file distributed with
    + * this work for additional information regarding copyright ownership.
    + * The ASF licenses this file to You under the Apache License, Version 2.0
    + * (the "License"); you may not use this file except in compliance with
    + * the License.  You may obtain a copy of the License at
    + *
    + *     http://www.apache.org/licenses/LICENSE-2.0
    + *
    + * Unless required by applicable law or agreed to in writing, software
    + * distributed under the License is distributed on an "AS IS" BASIS,
    + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    + * See the License for the specific language governing permissions and
    + * limitations under the License.
    + */
    +package org.apache.metron.bundles.bundle;
    +
    +/**
    + * Represents a bundle that contains one or more extensions.
    + */
    +public class Bundle {
    +
    +    private final BundleDetails bundleDetails;
    +
    +    private final ClassLoader classLoader;
    +
    +    public Bundle(final BundleDetails bundleDetails, final ClassLoader 
classLoader) {
    +        this.bundleDetails = bundleDetails;
    +        this.classLoader = classLoader;
    +
    +        if (this.bundleDetails == null) {
    +            throw new IllegalStateException("BundleDetails cannot be 
null");
    +        }
    +
    +        if (this.classLoader == null) {
    +            throw new IllegalStateException("ClassLoader cannot be null");
    --- End diff --
    
    The overall goal was just to ensure that if any code later on encounters a 
Bundle, it can be sure that the details and class loader are present. There 
isn't a realistic case in NiFi where you should encounter these exceptions, it 
was just being defensive.
    
    I think I got in the habit of using IllegalStateException here since at 
this point you are checking the member variables of the object and saying that 
something in the state of the object is not valid, as opposed to checking the 
arguments before assigning them which would maybe better to use 
IllegalArgumentException. 


> Create a plugin system for Metron based on 'NAR'
> ------------------------------------------------
>
>                 Key: METRON-777
>                 URL: https://issues.apache.org/jira/browse/METRON-777
>             Project: Metron
>          Issue Type: New Feature
>            Reporter: Otto Fowler
>            Assignee: Otto Fowler
>
> The success of the Metron project will be greatly dependent on community 
> participation, and with that the ability to adapt and extend Metron without 
> having to maintain a fork of the project.
> As organizations and individuals look to extend the Metron system with custom 
> parsers, enrichments, and stellar functions that may be proprietary in 
> nature, the ability to develop and deploy these extensions outside the Metron 
> code base is critically important.
> To that end, and after community discussion and proposal we create or 
> formalize the 'plugin' development story in Metron.  
> The proposal is to adapt the Apache Nifi NAR system for use in Metron.  This 
> will provide the system with:
> * archetype(s) for developer projects and independent development
> * defined packaging and metadata for 'plugin' products
> * loading and instantiation with classloader isolation capabilities
> * removing the necessity for shading plugin jars
> These capabilities will also enable other features, such as plugin lifecycle, 
> plugin configuration+redeployment, and other things.
> The plugin archetypes and their installation will be a followon



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