How to access a resource from a java library packed into its own .jar

Question

I have a library project with some resources that I would like to load and use. I would be using this library in another project so I have to pack the resources into the .jar. This is how that's achieved:

<resources>
    <resource>
        <directory>src/main/resources</directory>
    </resource>
</resources>

The problem comes when trying to retrieve the file, I do:

String resourceName = "myTemplateResource.json";
URL url = MyClass.class.getClassLoader().getResource(resourceName);

url is assigned a null value. It happens in the library's tests and in the dependant project. Any hint of what is missing?

Also tested using

MyClass.class.getResource("/myTemplateResourceName.json");

and

MyClass.class.getClassLoader().getResource("src/main/resources/myTemplateResource.json");

with the same result.

Answer 1

Use getResourceAsStream() method to load the resource from the .jar file as follows:

ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
InputStream inputStream = classLoader.getResourceAsStream(locaiton);

e.g.: If the file 'myTemplateResourceName.json' is located directly in the resources folder, use only the file name. It is wrong if you add a slash (/) in front of the path.

InputStream inputStream = classLoader.getResourceAsStream("myTemplateResourceName.json");

Note: You have to place the resource file in the main/resources (don't keep it in the test/resources section since that is not packed in the jar file) folder in the project which is being used to create the jar file.

Answer 2

There was something wrong with the filename that I was not able to find out. Renamed the file and now it's fine.

To answer my question:

First add the resource to the jar on the .pom file.

<resources>
    <resource>
        <directory>src/main/resources</directory>
    </resource>
</resources>

Then access your file.

URL url = MyClass.class.getClassLoader().getResource(resourceName);

From there you can get an InputStream. As simple as it looks.