17. Spring Beans and Dependency Injection
You are free to use any of the standard Spring Framework techniques to define your beans and their injected dependencies. For simplicity, we often find that using @ComponentScan
(to find your beans) and using @Autowired
(to do constructor injection) works well.
If you structure your code as suggested above (locating your application class in a root package), you can add @ComponentScan
without any arguments. All of your application components (@Component
, @Service
, @Repository
, @Controller
etc.) are automatically registered as Spring Beans.
The following example shows a @Service
Bean that uses constructor injection to obtain a required RiskAssessor
bean:
package com.example.service; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.stereotype.Service; @Service public class DatabaseAccountService implements AccountService { private final RiskAssessor riskAssessor; @Autowired public DatabaseAccountService(RiskAssessor riskAssessor) { this.riskAssessor = riskAssessor; } // ... }
If a bean has one constructor, you can omit the @Autowired
, as shown in the following example:
@Service public class DatabaseAccountService implements AccountService { private final RiskAssessor riskAssessor; public DatabaseAccountService(RiskAssessor riskAssessor) { this.riskAssessor = riskAssessor; } // ... }
Tip | |
---|---|
Notice how using constructor injection lets the |