Autowiring two beans implementing same interface - how to set default bean to autowire?

🚀 Autowiring two beans implementing the same interface - how to set default bean to autowire? 🤔

Have you ever come across a situation in your Spring application where you have multiple beans implementing the same interface? And you want to set a default bean to be autowired while still being able to explicitly use another bean? 🤷‍♂️ Well, you're not alone! Let's dive into this problem and find an easy solution together! 💪

🌟 Background:

In a Spring 2.5/Java/Tomcat application, imagine having two beans HibernateDeviceDao and JdbcDeviceDao, both implementing the DeviceDao interface. The HibernateDeviceDao bean is configured using component scanning, while the JdbcDeviceDao bean is configured separately. When starting the server, an exception is thrown because there are two matching beans for the DeviceDao interface.

💡 The question:

Our mission is to find a way to configure the beans so that we:

1. Don't have to make changes to existing classes that already have HibernateDeviceDao autowired.

2. Still be able to use the JdbcDeviceDao bean explicitly using the @Qualifier annotation.

💭 What have I already tried?

One approach I tried was setting the autowire-candidate property to false in the JdbcDeviceDao bean configuration. According to the Spring documentation, this should exclude the bean from being considered for autowiring. However, this didn't work as expected, and it resulted in an "Unsatisfied dependency" error.

✨ Solution:

After digging into the community, I found a suggestion by skaffman on Stack Overflow that can solve our problem. Instead of using the @Qualifier annotation, we can use the @Resource annotation with the name attribute set to the bean name.

Here's how we can do it:

@Resource(name = "jdbcDeviceDao")
private JdbcDeviceListItemDao jdbcDeviceDao;

By using @Resource with the name attribute, we can explicitly refer to the JdbcDeviceDao bean without changing the default autowiring behavior of the HibernateDeviceDao bean.

🎉 Conclusion:

Voila! 🎉 We've successfully tackled the challenge of autowiring two beans implementing the same interface, setting a default bean to autowire while still being able to use another bean explicitly. By leveraging the @Resource annotation with the name attribute, we can effortlessly handle this scenario in our Spring application.

If you found this blog post helpful or have other tricks up your sleeve, feel free to share your thoughts in the comments below! Let's keep the discussion going and empower each other with our Spring knowledge! 💬💪