JIRA API - Getting non-working days

Jira Development Jira Server
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1

I’m trying to create a servlet which outputs all the non-working days of a board in an ajile project.
This includes the user added non-working days: e.g. courntry specific holidays.
The JIRA software version I’m using is 8.14.1.
I’m thinking that I can use the classes WorkingDaysManager or WorkingDaysService to create a WorkingDaysConfig Object, and go from there to get the non-working days information that I need.
The problem is that I can’t find a way to get an instance of WorkingDaysManager or WorkingDaysService.
I’ve included the following maven package in my pom.xml file.

<dependency>
    <groupId>com.atlassian.jira.plugins</groupId>
    <artifactId>jira-greenhopper-plugin</artifactId>
    <version>6.7.7</version>
    <scope>provided</scope>
</dependency>

From there, I tried using the @ComponentImport spring annotation to include the components, but when I access the servlet page I get a 404 error and no error messages are output in the JIRA consol.
Here is the java file with the @ComponentImport.

package com.example;

import java.io.PrintWriter;
import java.io.IOException;

import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.atlassian.plugin.spring.scanner.annotation.imports.ComponentImport;

import com.atlassian.greenhopper.service.rapid.view.workingdays.WorkingDaysService;

public class NonWorkingDaysServlet extends HttpServlet {

    @ComponentImport
    private final WorkingDaysService workingDaysService;

    public NonWorkingDaysServlet(WorkingDaysService workingDaysService) {
        this.workingDaysService = workingDaysService;
    }

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException {
        PrintWriter printWriter = null;

        // Set output type
        response.setContentType("text/html");
        printWriter = response.getWriter();

        try {
            printWriter.println("Success");
        } catch (Exception e) {
            // Do nothing
        }
    }
}

Is there a way to get an instance of either of these classes in a plugin?
And if there is no way of doing that, is there another way to retreive non-working days in a plugin?