Computer scienceBackendSpring BootCore container

@Bean vs @Component

Chain autowiring

Report a typo

Imagine a Device needs a bean of a Printer:

Java

@Component
public class Device {

    private Printer printer;

    @Autowired
    public Device(Printer printer) {
        this.printer = printer;
    }
}

Kotlin

@Component
class Device @Autowired constructor(private val printer: Printer)

A Printer itself needs a bean of the InkSupply:

Java

@Component
public class Printer {

    @Autowired
    private InkSupply inkSupply;
}

@Configuration
public class CopyingConfiguration {

    @Bean
    public InkSupply getInkSupply(){
        return new InkSupply();
    }
}

Kotlin

@Component
class Printer {
    @Autowired
    private lateinit var inkSupply: InkSupply
}

@Configuration
class CopyingConfiguration {
    @Bean
    fun getInkSupply() : InkSupply {
        return InkSupply()
    }
}

Correctly place the beans in the "autowiring chain": the bean above is injected into the bean under it.

Put the items in the correct order

Device

Printer

InkSupply

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