The AmbiguousResolutionException Conundrum in Quarkus: A Step-by-Step Guide to Resolution with Custom MongoClient

Are you tired of encountering the dreaded AmbiguousResolutionException in your Quarkus application? Do you struggle to understand why it happens and how to fix it? Fear not, dear developer, for this article is here to guide you through the murky waters of dependency injection and MongoDB connectivity in Quarkus.

What is AmbiguousResolutionException?

The AmbiguousResolutionException is a runtime exception that occurs when Quarkus, a popular Java framework, is unable to resolve a dependency injection ambiguity. This means that Quarkus finds multiple instances of a particular type that match the injection point, and it can’t decide which one to use.

A Typical Scenario: MongoClient and Quarkus

One common scenario where AmbiguousResolutionException rears its head is when using a custom MongoClient with Quarkus. Let’s say you have a Quarkus application that connects to a MongoDB instance using a custom MongoClient. You’ve configured the MongoClient correctly, but when you run the application, you’re greeted with the dreaded AmbiguousResolutionException.

This is because Quarkus has multiple instances of MongoClient that match the injection point, and it can’t decide which one to use. But fear not, for we’re about to dive into the solution!

Resolving AmbiguousResolutionException with Custom MongoClient

Resolving this exception requires a combination of proper configuration, intelligent bean naming, and a dash of creativity. So, buckle up and let’s get started!

Step 1: Configure the Custom MongoClient

First things first, you need to configure your custom MongoClient. Create a new class that extends the MongoClient class:

import com.mongodb.client.MongoClient;
import com.mongodb.client.MongoClients;

public class CustomMongoClient extends MongoClient {
    public CustomMongoClient() {
        super(MongoClients.create("mongodb://localhost:27017"));
    }
}

This custom MongoClient connects to a MongoDB instance on localhost:27017. You can modify the connection string to match your MongoDB instance.

Step 2: Create a Producer Method

import javax.enterprise.context.ApplicationScoped;
import javax.enterprise.inject.Produces;

@ApplicationScoped
public class MongoClientProducer {
    
    @Produces
    public MongoClient produceMongoClient() {
        return new CustomMongoClient();
    }
}

This producer method returns an instance of your custom MongoClient, which will be used for injection later on.

Step 3: Qualify the Injection Point

Now, you need to qualify the injection point to avoid ambiguity. Add the following annotation to the injection point:

import javax.inject.Inject;
import javax.enterprise.inject.Qualifier;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Qualifier
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.FIELD)
public @interface CustomMongoClientQualifier {
}

public class MyService {
    
    @Inject
    @CustomMongoClientQualifier
    private MongoClient mongoClient;
    
    // Rest of the service implementation
}

This custom qualifier, @CustomMongoClientQualifier, helps Quarkus distinguish between multiple instances of MongoClient and inject the correct one.

Step 4: Update the Producer Method

Last but not least, you need to update the producer method to include the custom qualifier:

import javax.enterprise.context.ApplicationScoped;
import javax.enterprise.inject.Produces;

@ApplicationScoped
public class MongoClientProducer {
    
    @Produces
    @CustomMongoClientQualifier
    public MongoClient produceMongoClient() {
        return new CustomMongoClient();
    }
}

With this final step, Quarkus will inject the correct instance of MongoClient into your service, and the AmbiguousResolutionException will be a thing of the past!

Conclusion

In this article, we’ve explored the AmbiguousResolutionException in Quarkus and how it can be resolved when using a custom MongoClient. By configuring the custom MongoClient, creating a producer method, qualifying the injection point, and updating the producer method, you can successfully inject the correct instance of MongoClient and avoid the dreaded AmbiguousResolutionException.

Remember, the key to resolving this exception is to provide Quarkus with enough information to distinguish between multiple instances of MongoClient. By using custom qualifiers and producer methods, you can ensure that Quarkus injects the correct instance, and your application runs smoothly.

BONUS: Troubleshooting Tips

If you’re still encountering issues, here are some troubleshooting tips to help you resolve the AmbiguousResolutionException:

• Verify that you’ve correctly configured the custom MongoClient and producer method.
• Check that the injection point is properly qualified with the custom qualifier.
• Ensure that the producer method returns an instance of the custom MongoClient.
• Review your application’s configuration to ensure that there are no duplicate or conflicting MongoClient instances.

Additional Resources

If you want to dive deeper into Quarkus and MongoDB connectivity, check out the following resources:

Resource	Description
Quarkus MongoDB Guide	A comprehensive guide to using MongoDB with Quarkus.
Quarkus MongoDB Extension	The official Quarkus MongoDB extension repository on GitHub.
MongoDB Documentation	The official MongoDB documentation, covering everything from getting started to advanced topics.

With these resources and the steps outlined in this article, you’ll be well-equipped to tackle the AmbiguousResolutionException and create robust MongoDB-powered applications with Quarkus.

Final Thoughts

In conclusion, resolving the AmbiguousResolutionException in Quarkus with a custom MongoClient requires a combination of proper configuration, intelligent bean naming, and a dash of creativity. By following the steps outlined in this article and troubleshooting common issues, you can ensure that your Quarkus application connects seamlessly to your MongoDB instance and runs smoothly.

Happy coding, and may your applications be AmbiguousResolutionException-free!

Here are the 5 Questions and Answers about “AmbiguousResolutionException in Quarkus with custom MongoClient”:

Frequently Asked Question

Get the answers to the most frequently asked questions about handling AmbiguousResolutionException in Quarkus when using a custom MongoClient.