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https://issues.apache.org/jira/browse/HADOOP-12490?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16704969#comment-16704969
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Jonathan Eagles commented on HADOOP-12490:
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[~mjacob_otto], this will have to be done differently since jdk9+ doesn't
support this capability by default. TEZ-3860
> Add default resources to Configuration which are not inside the class path
> --------------------------------------------------------------------------
>
> Key: HADOOP-12490
> URL: https://issues.apache.org/jira/browse/HADOOP-12490
> Project: Hadoop Common
> Issue Type: Improvement
> Components: conf
> Affects Versions: 2.7.1
> Reporter: Matthias Jacob
> Assignee: Matthias Jacob
> Priority: Major
> Attachments: HADOOP-12490.001.patch
>
>
> *Problem*
> It is currently not possible to add default resources to
> {{org.apache.hadoop.conf.Configuration}} that are not included in the class
> path.
> We need to add resources to {{org.apache.hadoop.conf.Configuration}} that are
> not included in the class path. Currently, the only way to do this is to use
> {{addResource(URL)}} or {{addResource(Path)}} which both are instance
> methods. However, a library we work with creates Configuration instances
> internally that we cannot access. So we need to add them as default resources
> in order to make them available to all subsequent Configuration instances
> (and those existing instances where {{loadDefaults}} equals {{true}}, of
> course).
> *Solution*
> The proposed solution is to add the following static methods:
> {code}
> public static synchronized void addDefaultResource(URL url);
> public static synchronized void addDefaultResource(Path file);
> {code}
> Please see the attached patch for details.
> *Example*
> In order to initialize the Configuration correctly, what we need to do
> currently is as follows:
> {code}
> // Set resource paths for the class loader
> File ffile = new File("/path/to/conf/dir");
> URL url = ffile.toURI().toURL();
> URLClassLoader systemClassLoader = (URLClassLoader)
> getClass().getClassLoader();
> Class<URLClassLoader> classLoaderClass = URLClassLoader.class;
> Method method = classLoaderClass.getDeclaredMethod("addURL", new
> Class[]{URL.class});
> method.setAccessible(true);
> method.invoke(systemClassLoader, new Object[]{url});
> //-----------------------------
> // Read cluster config
> for (File f : ffile.listFiles()) {
> if(f.getName().toLowerCase().endsWith(".xml")) {
> Configuration.addDefaultResource(f.getName());
> }
> }
> {code}
> As you can see, we currently need to manipulate the class path through
> reflection which is kind of dirty.
> With the proposed solution, the same (adding default resources from outside
> the class path) can be achieved doing the following:
> {code}
> // Set resource paths for the class loader
> File ffile = new File("/path/to/conf/dir");
> //-----------------------------
> // Read cluster config
> for (File f : ffile.listFiles()) {
> if(f.getName().toLowerCase().endsWith(".xml")) {
> Configuration.addDefaultResource(new Path(f.getAbsolutePath()));
> }
> }
> {code}
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