Spring "Parameter 0 of constructor required a bean that could not be found" - Fix in CI

By Kaveh Alemi·Latchkey

Spring tried to inject a constructor parameter and found no bean of the required type in the context. The class is asking for a collaborator the container was never told how to build.

What this error means

Context startup fails with Parameter 0 of constructor in com.example.Service required a bean of type 'com.example.Repo' that could not be found. Spring usually appends an "Action" suggesting you define such a bean. The app or @SpringBootTest aborts before any request is served.

java

***************************
APPLICATION FAILED TO START
***************************

Description:

Parameter 0 of constructor in com.example.OrderService required a bean of
type 'com.example.OrderRepository' that could not be found.

Action:

Consider defining a bean of type 'com.example.OrderRepository' in your
configuration.

Common causes

The bean type is not a component or not scanned

The dependency class lacks @Component/@Repository/@Service, or it lives in a package outside the @SpringBootApplication scan root, so it never becomes a bean.

A @Bean factory method is missing

For third-party types you do not own (a client, a template), there is no @Bean method producing one, so the container has no candidate.

A test slice excludes the bean

A @WebMvcTest/@DataJpaTest slice only loads part of the context. A collaborator outside that slice is absent unless mocked or imported.

How to fix it

Make the dependency a scanned bean

Annotate the implementation and ensure it is under the application package so component scanning finds it.

Java

@Repository // now a bean; package must be under the @SpringBootApplication root
public class OrderRepositoryImpl implements OrderRepository { /* ... */ }

Provide a @Bean for types you do not own

Declare a factory method in a @Configuration class for any collaborator you cannot annotate.

Java

@Configuration
public class Clients {
  @Bean
  OrderRepository orderRepository(DataSource ds) {
    return new JdbcOrderRepository(ds);
  }
}

Mock the bean in a test slice

If the failure is only in a sliced test, supply the missing collaborator as a mock rather than loading the full context.

java

@WebMvcTest(OrderController.class)
class OrderControllerTest {
  @MockBean OrderService orderService; // satisfies the slice
}

How to prevent it

Keep all components under the @SpringBootApplication package so scanning is automatic.
For external types, define @Bean factories explicitly rather than relying on scanning.
Run @SpringBootTest in CI so a missing bean fails fast in the pipeline, not in production.

Frequently asked questions

What causes ""required a bean that could not be found""?

The dependency class lacks @Component/@Repository/@Service, or it lives in a package outside the @SpringBootApplication scan root, so it never becomes a bean.

How do I fix "required a bean that could not be found"?