In Guice 2 or 3, exists so called Assisted/Partial Inject described here. With this, Guice synthesizes factory implementation (implementing my interface) for my object and s
The following does exactly what i asked for. Though, it does not synthesize the implementation of the factory, it is good enough as the factory has access to the injection context so that can use other beans (injectable artifacts) during construction. It uses java based @Configuration
instead of XML, but it will work with XML too.
The factory interface:
public interface Robot {
}
// Implementation of this is to be injected by the IoC in the Robot instances
public interface Brain {
String think();
}
public class RobotImpl implements Robot {
private final String name_;
private final Brain brain_;
@Inject
public RobotImpl(String name, Brain brain) {
name_ = name;
brain_ = brain;
}
public String toString() {
return "RobotImpl [name_=" + name_ + "] thinks about " + brain_.think();
}
}
public class RobotBrain implements Brain {
public String think() {
return "an idea";
}
}
// The assisted factory type
public interface RobotFactory {
Robot newRobot(String name);
}
// this is the Spring configuration showing how to do the assisted injection
@Configuration
class RobotConfig {
@Bean @Scope(SCOPE_PROTOTYPE)
public RobotFactory robotFactory() {
return new RobotFactory() {
@Override
public Robot newRobot(String name) {
return new RobotImpl(name, r2dxBrain());
}
};
}
@Bean @Scope(SCOPE_PROTOTYPE)
public Brain r2dxBrain() {
return new RobotBrain();
}
}
The test code:
public class RobotTest {
@Test
public void t1() throws Exception {
ApplicationContext ctx = new
AnnotationConfigApplicationContext(RobotConfig.class);
RobotFactory rf = ctx.getBean(RobotFactory.class);
assertThat(rf.newRobot("R2D2").toString(),
equalTo("RobotImpl [name_=R2D2] thins about an idea"));
}
}
This achieves exactly what Guice does. The tricky difference is the Scope
. Spring's default scope is Singleton
and Guice's is not (it is prototype).