Ingeniería Web

Spring

Inyección de dependencias

Created by Juan Manuel Dodero / @jmdodero

transiciones

Cube - Page - Concave - Zoom - Linear - Fade - None - Default

temas

Default - Sky - Beige - Simple - Serif - Night
Moon - Solarized

Ejemplo

Versión 1

ATM Implementation does not care about the transport

						
public interface AutomatedTellerMachine {
    void deposit(BigDecimal bd);
    void withdraw(BigDecimal bd);
}

public interface ATMTransport {
    void communicateWithBank(byte [] datapacket);
}

public class AutomatedTellerMachineImpl implements AutomatedTellerMachine{
    
    private ATMTransport transport;
    
    public void deposit(BigDecimal bd) {
       ...
       transport.communicateWithBank(...);
    }

    public void withdraw(BigDecimal bd) {
       ...
       transport.communicateWithBank(...);
    }

    public void setTransport(ATMTransport transport) {
       this.transport = transport;
    }
}

public class SoapAtmTransport implements ATMTransport {
    public void communicateWithBank(byte[] datapacket) {
       ...
    }
}

public class StandardAtmTransport implements ATMTransport {
    public void communicateWithBank(byte[] datapacket) {
       ...
    }
}

public class SimulationAtmTransport implements ATMTransport {
    public void communicateWithBank(byte[] datapacket) {
       ...
    }
}
					

Versión 1

DI without Spring

public class AtmMain {       
    public void main (String[] args) {
        AutomatedTellerMachine atm = new AutomatedTellerMachineImpl();
        ATMTransport transport = new SoapAtmTransport();
        /* Inject the transport. */           
        ((AutomatedTellerMachineImpl)atm).setTransport(transport);
        atm.withdraw(new BigDecimal("10.00"));
        atm.deposit(new BigDecimal("100.00"));
    }
}

ATMTransport transport = new SimulationAtmTransport();
((AutomatedTellerMachineImpl)atm).setTransport(transport);

					

Versión 2

DI with Spring

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class AtmMain {       
    public static void main (String[] args) {
        ApplicationContext appContext = new ClassPathXmlApplicationContext("classpath:./spring/applicationContext.xml");
        AutomatedTellerMachine atm = (AutomatedTellerMachine) appContext.getBean("atm");                
        atm.withdraw(new BigDecimal("10.00"));                
        atm.deposit(new BigDecimal("100.00"));
    }
}
					

Versión 2

ApplicationContext XML

Versión 3

Using constructor to inject dependency

Versión 3

Application context

Versión 3

Constructor

public class AutomatedTellerMachineImpl implements AutomatedTellerMachine{    

    private ATMTransport transport;
    
    public AutomatedTellerMachineImpl (ATMTransport transport) {
        this.transport = transport;
    }

}
					

Versión 4

Olvidamos inyectar la dependencia...

Versión 4

Pedimos a spring que lo compruebe: @Required

import org.springframework.beans.factory.annotation.Required;

public class AutomatedTellerMachineImpl implements AutomatedTellerMachine{
    
    private ATMTransport transport;

    @Required
    public void setTransport(ATMTransport transport) {
        this.transport = transport;
    }
}
					

Versión 4

Definimos un transporte por defecto: @Autowire y @Qualifier

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;

public class AutomatedTellerMachineImpl implements AutomatedTellerMachine{        
    @Autowired (required=true)
    @Qualifier ("standardTransport")
    private ATMTransport transport;
}
					

Versión 4

Application context con anotaciones

Versión 4

Versión 4

XML DI tiene precedencia sobre las anotaciones