classLoader.getResource(filename) not returning existent file (returning null)

Question

I'm trying to load a .json file for testing purposes on a Beam pipeline.

The code looks like

...
public class ExtractCsvMessageTest {
  @Rule public final transient TestPipeline pipeline = TestPipeline.create();

  final String filepath = "com/project/functions/ExtractCsvMessageTest/";
  final String filename = filepath + "comma_delimited.json";
  final ClassLoader classLoader = getClass().getClassLoader();

  final File commaDelimited = new File(classLoader.getResource(filename).getFile());
...

After running the debugger, I can see the line throwing the error is:

final File commaDelimited = new File(classLoader.getResource(filename).getFile());

My path looks like

test
    ├── java
    │   └── com
    │       └── project
    │           ├── functions
    │           │   ├── ExtractCsvMessageTest.java
    │           └── transforms
    └── resources
        └── com
            └── project
                └── functions
                    └── ExtractCsvMessageTest
                        └── comma_delimited.json

There are similar questions on here but I can't find anything which solved this issue.

Also, I'm using VSCode and I just created the path from resources manually.

Finally, my .classpath is

<?xml version="1.0" encoding="UTF-8"?>
<classpath>
    <classpathentry kind="src" output="bin/main" path="src/main/java">
        <attributes>
            <attribute name="gradle_scope" value="main"/>
            <attribute name="gradle_used_by_scope" value="main,test"/>
        </attributes>
    </classpathentry>
    <classpathentry kind="src" output="bin/main" path="src/main/resources">
        <attributes>
            <attribute name="gradle_scope" value="main"/>
            <attribute name="gradle_used_by_scope" value="main,test"/>
        </attributes>
    </classpathentry>
    <classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-1.8/"/>
    <classpathentry kind="con" path="org.eclipse.buildship.core.gradleclasspathcontainer"/>
    <classpathentry kind="output" path="bin/default"/>
    <classpathentry kind="src" path="src/test/java" output="build/classes/test">
        <attributes>
            <attribute name="test" value="true" />
        </attributes>
    </classpathentry>
</classpath>

tl:dr

Why is

final File commaDelimited = new File(classLoader.getResource(filename).getFile());

returning null?

Answer 1

This was a classpath issue, as suspected.

I solved it in VSCode by triggering the command palette with Cmd + Shift + P and selecting

Java: Clean the Java language server workspace

This in turn updated the .classpath file.

After exitting and launching VSCode again, everything was working again.