Package com.tccc.kos.commons.core.context.annotations

Annotation Interface Autowired

@Target(FIELD)
@Retention(RUNTIME)
@Inherited
public @interface Autowired

Annotation that informs the BeanContext that a dependent field needs its object reference injected, which is also known as autowired.

Examples

1) Simple autowiring

After an instance of MyClass1 is created, the myClass2 and myClass3 objects are automatically inserted into their respective fields by the kOS bean context.

 
      public class MyClass1 {

          @Autowired
          private MyClass2 myClass2;

          @Autowired
          private MyClass3 myClass3;
      }
 
 

2) Phased autowiring

Due to the asynchronous nature of the hardware associated with embedded devices, it's common to want to inject sets of beans in phases. In other words, set #1 is injected first, then set #2, then set #3, etc. kOS provides a way to do this using the "phase" parameter.

In this example, the myClass2 object is injected during "Phase-X", while the myClass3 object is injected during "Phase-Y".

 
      public class MyClass1 {

          @Autowired(phase = "Phase-X")
          private MyClass2 myClass2;

          @Autowired(phase = "Phase-Y")
          private MyClass3 myClass3;
      }
 
 

In your application startup code, you'd write something like this:

 
      public MyKosApp {

          @Autowired
          private BeanContext ctx;

          public init() {
              // . . .
              // Inject all beans associated with the "Phase-X" phase:
              ctx.update("Phase-X");
              // (possibly perform other operations)
              // Inject all beans associated with the "Phase-Y" phase:
              ctx.update("Phase-Y");
              // . . .
          }
      }
 
 

More practically speaking, you might want to autowire filesystem beans first, followed by network beans, then database beans, then hardware beans, and finally the user interface beans.

3) Qualified (named objects) autowiring

Sometimes, like when you have multiple instances of the same class, you need another way to identify each. For such occasions, use the qualifier parameter, which allows you to differentiate between the two instances.

 
      public class MyClass1 {

          @Autowired(qualifier = "Pump-1")
          private MyClass2 myClass2a;

          @Autowired(qualifier = "Pump-2")
          private MyClass2 myClass2b;
      }
 
 

In your application startup code, you'd write something like this:

 
      public MyKosApp {

          public init() {
              // . . .
              // Create the two instances:
              MyClass2 myClass2a = new MyClass2(optionsA);
              MyClass2 myClass2b = new MyClass2(optionsB);
              // Add them to the context, being sure to name them:
              ctx.add("Pump-1", myClass2a);
              ctx.add("Pump-2", myClass2b);
              // . . .
          }
      }
 
 

4) Ignoring "ready"

Use the ignoreReady flag when you don't need to wait for the autowired bean to become ready before marking the referencing bean ready. This can be used to resolve circular dependencies. The referencing bean can use isReady() or whenReady() to detect when the referenced bean becomes ready without blocking startup.

 
      public class MyClass1 {
          @Autowired(ignoreReady = true)
          private MyClass2 myClass2;
      }
 
 

5) Optional autowiring

Setting the required flag false allows this autowire to fail without generating an error or throwing an exception.

 
      public class MyClass1 {
          @Autowired(required = false)
          private MyClass2 myClass2;
      }
 
 

Since:

1.0

Version:

2022-08-30

See Also:

• BeanContext

Optional Element Summary

Optional Elements

Modifier and Type	Optional Element	Description
boolean	ignoreReady	Set this flag true when you do not want to wait for the autowired bean to become ready before marking the referencing bean ready.
String	phase	The phase to evaluate this annotation in.
String	qualifier	The qualifier that matches a bean with the same name.
boolean	required	Setting this flag false allows this autowire to fail without throwing an error.

Element Details

phase

String phase

The phase to evaluate this annotation in.

Returns:

the name of the phase when this bean should be injected

Default:

""

qualifier

String qualifier

The qualifier that matches a bean with the same name.

Returns:

the name of the bean associated with this object

Default:

""

ignoreReady

boolean ignoreReady

Set this flag true when you do not want to wait for the autowired bean to become ready before marking the referencing bean ready.

Returns:

true if this autowire is not necessary for the containing bean to become ready

Default:

false

required

boolean required

Setting this flag false allows this autowire to fail without throwing an error.

Returns:

true if the autowire requires a non-null value

Default:

true