在Web应用程序中初始化自动装配成员所需的最低配置是什么？

Question

What's the minimal configuration needed to have the following class member to be initialized using the @Autowired annotations:

public class A {
  @Autowired
  private B b;
  // ...
}

When invoking A a = new A(), I'd like b to be initialized from a predefined bean without the need to configure it in code.

Probably some files are needed: A.java , web.xml , spring-context.xml (for configuring B) and jars (spring and a jar containing B).

What's the minimal needed configuration and files content?

Answer 1

Based on this post , I created the this project . Steps to have B initiated:

1. Download and extract the compressed folder.
2. Run mvn clean install .
3. Copy the war (spring-autowired-1.0-SNAPSHOT.war) from the target to a web server's webapps folder.
4. Run the server. (for tomcat: ./catalina.sh run)
5. Call the API and see B's hascode - curl -X GET http://localhost:8080/spring-autowired-1.0-SNAPSHOT/rest/a/a .
6. See b is initialized - not null.

The actual class:

@Component
@Path("/a")
public class A {

    @Autowired
    B b;

    @GET
    @Path("/a")
    public String a() {
        return b.toString();
    }
}

* The difference between my implementation vs. mkyong's is that my pom has less dependencies and @Autowired member is not an interface.

Answer 2

If for some reason you cant configure class A to be a bean in your application context you can have class A implement SpringBeanAutowingSupport. This works in a web environment.

The SpringBeanAutowingSupport default constructor looks up the application context from the request. It then injects the dependencies.

public class A extends SpringBeanAutowiringSupport{
  @Autowired
  private B b;
}