JiaLiangC opened a new pull request, #3913:
URL: https://github.com/apache/ambari/pull/3913
## What changes were proposed in this pull request?
Improve View Loading Mechanism in Ambari
The current implementation of the getViewConfigFromArchive method in
ViewArchiveUtility.java is not robust enough when loading views via the SPI
mechanism in Ambari. The purpose of this method is to retrieve views from a
specified JAR file and instantiate a ViewConfig object containing the view
metadata.
Problem Description
The method currently uses the following code to load the view configuration:
```JAVA
ClassLoader cl = URLClassLoader.newInstance(new
URL[]{archiveFile.toURI().toURL()});
InputStream configStream = cl.getResourceAsStream(VIEW_XML);
```
In normal scenarios, all views are stored in
/var/lib/ambari-server/resources/views, and this works as expected. However,
when ambari-admin-3.0.0.0-SNAPSHOT.jar or any other view JAR file exists in the
/usr/lib/ambari-server/ directory, the call to
cl.getResourceAsStream(VIEW_XML); will always return the first view loaded from
/usr/lib/ambari-server/, rather than the intended views.xml file from the
specified archiveFile. This results in the retrieval of incorrect configuration
and can lead to a corrupted view system.
Proposed Solution
To resolve this issue, we propose to modify the loading mechanism to prevent
the delegation of the class loader, ensuring that the correct resource is
loaded from the specified JAR file. By creating a URLClassLoader with a parent
class loader set to null, we can isolate the resource loading process:
```JAVA
try (URLClassLoader cl = new URLClassLoader(new
URL[]{archiveFile.toURI().toURL()}, null)) {
// Load the configuration stream safely
}
```
This change will ensure that the method only loads resources from the
specified JAR file, avoiding conflicts with other JARs present in the classpath.
This improvement will enhance the reliability of the view loading mechanism
in Ambari, preventing configuration errors and ensuring that the correct view
metadata is always retrieved. We recommend merging this change to improve the
robustness of the system.
## How was this patch tested?
manual test and unit tests
Before the patch was applied, an error occurred when clicking the Ambari
Manager button.
After applying the patch, everything functions properly.
(Please explain how this patch was tested. Ex: unit tests, manual tests)
(If this patch involves UI changes, please attach a screen-shot; otherwise,
remove this)
Please review [Ambari Contributing
Guide](https://cwiki.apache.org/confluence/display/AMBARI/How+to+Contribute)
before opening a pull request.
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