Dependency injection in Jira plugins

Written on December 1, 2019

Do you need to simplify your code by automatically injecting required instances into your objects? Dependency injection is the answer.

These instructions have been tested in JIRA 7.13.9 with Atlassian Spring Scanner 1.2.13.

Jira uses the Atlassian Spring Scanner that makes this quite easy. The best place to learn about it is the readme file of the Atlassian Spring Scanner Bitbucket repository.

Let’s look at an example. If we have an interface named Helper and an implementing class HelperImpl, all we need to do to make it available for injection, is to use @Named annotation on the implementing class:

import javax.inject.Named;
import com.example.jira.plugin.api.Helper;

@Named
public class HelperImpl implements Helper {

  @Override
  public String sayHello() {
    return "Hello.";
  }

}

To have the Helper implementation injected into another class (in this case a REST resource), we’ll annotate it’s constructor with @Inject:

import javax.inject.Inject;
import com.example.jira.plugin.api.Helper;
// ... rest of the imports

/**
 * A resource of message.
 */
@Path("/message")
public class MyRestResource {
    // store Helper in private property
    private Helper helper;
    
    @Inject
    public MyRestResource(Helper helper) {
      this.helper = helper;
    }
    
    @GET
    @AnonymousAllowed
    @Produces({MediaType.APPLICATION_JSON, MediaType.APPLICATION_XML})
    public Response getMessage()
    {
      // return the message from the Helper implementation
      return Response.ok(new MyRestResourceModel(helper.sayHello())).build();
    }
}

The example above works when injecting an object from the same plugin. If you would like to inject an object from Jira itself (or another plugin), add the @ComponentImport annotation to the constructor parameter.

For example, if we want to use the ApplicationProperties in our class, we can do it like this:

import javax.inject.Inject;
import com.example.jira.plugin.api.Helper;

import com.atlassian.plugin.spring.scanner.annotation.imports.ComponentImport;
// ... rest of the imports

/**
 * A resource of message.
 */
@Path("/message")
public class MyRestResource {
    // store Helper in private property
    private Helper helper;
    // store ApplicationProperties
    private ApplicationProperties applicationProperties;
    
    @Inject
    public MyRestResource(Helper helper, @ComponentImport ApplicationProperties applicationProperties) {
      this.helper = helper;
      this.applicationProperties = applicationProperties;
    }
    
    // rest of the code
}

And that’s all. Just use @Named on your components, @Inject on constructors that use your components and @ComponentImport when importing stuff outside your plugin.

JIRA Programming

Dependency injection in Jira plugins

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