Tapestry IoC constructor and injection

问题

I have the following class:

public class MyClass {
    @Inject
    private MyAnotherClass myAnotherClass;

    public MyClass() {
        //Perform operations on myAnotherClass.
    }
}

I need to do some things in constructor which require an instance of myAnotherClass. Unfortunately myAnotherClass is injected after code in constructor is ran, which means I am performing operations on null...

I could of course instantiate it the classic way (MyAnotherClass myAnotherClass = new MyAnotherClass()) directly in constructor, but I don't think it is the right thing to do in this situation.

What solutions would you suggest to solve this problem?

回答1:

Best option:

public class MyClass {
  private final MyAnotherClass myAnotherClass;

  public MyClass(MyAnotherClass other) {
    this.myAnotherClass = other;
    // And so forth
  }
}

T5-IoC will then use constructor injection so there's no need to 'new' up MyClass yourself. See Defining Tapestry IOC Services for more info.

Alternatively:

public class MyClass {
  @Inject
  private MyAnotherClass myAnotherClass;

  @PostInjection
  public void setupUsingOther() {
    // Called last, after fields are injected
  }
}

来源：https://stackoverflow.com/questions/15121308/tapestry-ioc-constructor-and-injection