dependency injection - Spring DI (Beans) with multiple concretes…picking one of them

Question

I have a similar question here

Guice with multiple concretes......picking one of them

with a solution for Guice.

But I have a different project using spring di (beans), but with the same kind of issue.

I have an interface with N number of concretes. (3 here)

public interface OrderProcessorInterface {

  void ProcessOrder(String preferredShipperAbbreviation, Order ord);

}

public class FedExShipper implements ShipperInterface {

  private Log logger;

  public FedExShipper(Log lgr) {

    if (null == lgr) {
      throw new IllegalArgumentException("Log is null");
    }

    this.logger = lgr;
  }

  public void ShipOrder(Order ord) {
    this.logger.info("I'm shipping the Order with FexEx");
  }
}


public class UpsShipper implements ShipperInterface {

  private Log logger;

  public UpsShipper(Log lgr) {

    if (null == lgr) {
      throw new IllegalArgumentException("Log is null");
    }

    this.logger = lgr;
  }

  public void ShipOrder(Order ord) {
    this.logger.info("I'm shipping the Order with Ups");
  }
}


public class UspsShipper implements ShipperInterface {

  private Log logger;

  public UspsShipper(Log lgr) {

    if (null == lgr) {
      throw new IllegalArgumentException("Log is null");
    }

    this.logger = lgr;
  }

  public void ShipOrder(Order ord) {
    this.logger.info("I'm shipping the Order with Usps");
  }
}

........

Then I have a class that needs to know about ALL THREE concretes.

import java.util.Collection;
import java.util.Set;

import org.apache.commons.logging.Log;

public class OrderProcessorImpl implements OrderProcessorInterface {

  private Log logger;
  private java.util.Map<String, javax.inject.Provider<ShipperInterface>> shipperProviderMap;

  public OrderProcessorImpl(Log lgr, java.util.Map<String, javax.inject.Provider<ShipperInterface>> spMap) {

    if (null == lgr) {
      throw new IllegalArgumentException("Log is null");
    }

    if (null == spMap) {
      throw new IllegalArgumentException("Provider<ShipperInterface> is null");
    }

    this.logger = lgr;
    this.shipperProviderMap = spMap;
  }

  public void ProcessOrder(String preferredShipperAbbreviation, Order ord) {
    this.logger.info(String.format("About to ship. (%1s)", preferredShipperAbbreviation));


    ShipperInterface foundShipperInterface = this.FindShipperInterface(preferredShipperAbbreviation);
    foundShipperInterface.ShipOrder(ord);
  }

  private ShipperInterface FindShipperInterface(String preferredShipperAbbreviation) {

    ShipperInterface foundShipperInterface = this.shipperProviderMap.get(preferredShipperAbbreviation).get();

    if (null == foundShipperInterface) {
      throw new NullPointerException(
          String.format("ShipperInterface not found in shipperProviderMap. ('%1s')", preferredShipperAbbreviation));
    }

    return foundShipperInterface;
  }
}

=============

Basically, I want to call the method, pass in a string argument, and have it choose the concrete for me. (if my real code, this is via a database value, but for the demo code, this is good enough)

Order ord = new Order();
ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");
BeanFactory factory = context;

OrderProcessorInterface opi = context.getBean(OrderProcessorImpl.class);
opi.ProcessOrder("myFedExName", ord); /* friendlyName would be nice, but fully qualified concrete name also assceptable */

My Spring Configuration is via xml:

 <bean id="theLoggerBean"
       class="org.apache.commons.logging.impl.Log4JLogger">
       <constructor-arg value="log" />
 </bean>    



<bean id="fedExBean"
    class="com.me.FedExShipper">
    <constructor-arg ref="theLoggerBean"></constructor-arg>
</bean>


<bean id="uspsExBean"
    class="com.me.FedExShipper">
    <constructor-arg ref="theLoggerBean"></constructor-arg>
</bean>


<bean id="upsExBean"
    class="com.me.FedExShipper">
    <constructor-arg ref="theLoggerBean"></constructor-arg>
</bean>

..........

================================

<bean id="OrderProcessorImplBean"
    class="com.me.OrderProcessorImpl">

    <constructor-arg ref="theLoggerBean"></constructor-arg>

    <constructor-arg ref="How do I do N Number of ShipperInterfaces Here ??"></constructor-arg>

</bean>

So I want to xml configure the 3 concretes.

And then inject them into the class.

But where I have "How do I do N Number of ShipperInterfaces Here ??", I have no idea what to do.

JSR 330 implementation preferred, but will take anything.

THANKS

Note, in the other question (the Guice one), this was also a possiblity for the constructor of the OrderProcessor:

public class OrderProcessorImpl implements OrderProcessorInterface {

  private Log logger;
  Set<ShipperInterface> shippers;

  public OrderProcessorImpl(Log lgr, Set<ShipperInterface> shprs) {

    if (null == lgr) {
      throw new IllegalArgumentException("Log is null");
    }

    if (null == shprs) {
      throw new IllegalArgumentException("ShipperInterface(s) is null");
    }

    this.logger = lgr;
    this.shippers = shprs;
  }

  public void ProcessOrder(String preferredShipperAbbreviation, Order ord) {
    this.logger.info(String.format("About to ship. (%1s)", preferredShipperAbbreviation));

    for (ShipperInterface sh : shippers) {
      this.logger.info(String.format("ShipperInterface . (%1s)", sh.getClass().getSimpleName()));
    }

  }
}

Answer 1

Something like this should work. This uses @Autowired and not xml configuration:

@org.springframework.stereotype.Service
public class OrderProcessorImpl implements OrderProcessorInterface {

    private List<ShipperInterface> shipperProviders;

    private Map<String, ShipperInterface> shipperProvidersMap = new HashMap<>();

    @Autowired
    public void setShipperProviders(List<ShipperInterface> shipperProviders) {
        this.shipperProviders= shipperProviders;

        this.shipperProviders.stream().forEach(p->shipperProvidersMap .put(/* your code for getting the key */, p));
    }

Gradle dependency hint:

compile group: 'org.springframework', name: 'spring-context', version: '5.1.9.RELEASE'