Spring Autowired in Web Service not working

Question

I must be missing something simple, but I'm having trouble getting an Autowired property to be assigned to a bean. All similar answers posted here seem to revolve around one of three solutions:

1. extend SpringBeanAutowiringSupport
2. use <context:component-scan base-package="..." /> in applicationContext.xml
3. use <context:annotation-config /> in applicationContext.xml

I tried to make a minimalist bean to represent my DAO and inject it into a Web Service.

DAO interface:

package wb;
public interface FooDAO {
    public String doNothing();
}

DAO implementation:

package wb;
import org.springframework.stereotype.Component;

@Component
public class FooDAOImpl implements FooDAO {
    public FooDAOImpl() {
        System.out.println("FooDAOImpl: Instantiated " + this);
    }

    @Override
    public String doNothing() {
        System.out.println("FooDAOImpl: doNothing() called");
        return "Did nothing!";
    }
}

Web Service with injection:

package ws;

import javax.jws.WebService;
import javax.jws.WebMethod;
import javax.jws.WebResult;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.context.support.SpringBeanAutowiringSupport;
import wb.FooDAO;

@WebService(serviceName = "WS")
public class WS extends SpringBeanAutowiringSupport {

    @Autowired(required = true)
    private FooDAO fooDAO;

    @WebMethod(exclude = true)
    public void setFooDAO(FooDAO fooDAO) {
        this.fooDAO = fooDAO;
        System.out.println("WS: fooDAO set = " + fooDAO);
    }

    public WS() {
        System.out.println("WS: WS bean instantiated!");
    }

    @WebMethod(operationName = "doNothing")
    @WebResult(name = "whatDidIDo")
    public String doNothing() {
        System.out.println("WS: doNothing() says DAO = " + fooDAO);
        return fooDAO == null ? "Could not do nothing!" : fooDAO.doNothing();
    }
}

applicationContext.xml content within the beans tags:

<context:annotation-config />
<context:component-scan base-package="ws"/>

<bean id="fooDAO" class="wb.FooDAOImpl" />

This was all created in the latest NetBeans, in a project created with Spring and Hibernate frameworks. When I deploy to JBoss, and the app starts up, I get the expected Bean instantiation:

11:01:46,767 INFO  [stdout] (MSC service thread 1-6) WS: WS bean instantiated!
11:01:47,571 INFO  [stdout] (MSC service thread 1-15) FooDAOImpl: Instantiated wb.FooDAOImpl@11176682

Once I call the web service, the log also reports:

11:03:07,097 INFO  [stdout] (http--127.0.0.1-8080-1) WS: doNothing() says DAO = null

What am I missing?

Solution

SpringBeanAutowiringSupport must be a bean. You need to annotate that class with @Service or another annotation such as @Component that indicates a class should be a bean when component scanning occurs. These will be picked up by Spring and made into beans.

Remember that in order to be a participant in autowiring, such as having another bean injected, the class must be a bean itself and managed by Spring's IOC container.

Comments

[user3207820]

Thanks; could have sworn that's one of the things I'd tried previously. When I add @Component, it works.

[Kevin Bowersox]

@user3207820 Glad I could help. I struggled with some the same concepts early on when using Spring. Anytime you use the new keyword you really need to pause and wonder if its appropriate.

[user3207820]

The WS instance created during App startup gets an auto-wired DAOImpl. But when calling the web service, a different WS instance is created to field the requests, and THAT instance doesn't get one. Weird. Anyway, thanks again.

[Jurgen Camilleri]

I'm experiencing the same exact thing as the above comment. I can't get the instance created when calling the web service to have the autowired fields. Am I doing something wrong with how I'm creating the web service? Or did I not follow the solution correctly? Spring is definitely creating the WS class as a bean, but it's not the same instance used when calling the service.