Java 包装子 class 方法，以便首先调用父方法，然后调用子 class 方法

Question

I have a class that has a bunch of methods. This class is copied in several different places with slight variances in what each method does. What I want to do is move the common code into a class with similar method signatures, but the parameter is a base class that the object in the parameter of the other class inherits. When the method in the inherited class is called, I want it to redirect to the base class method, do that code, then somehow call back into the inherited class method. I cannot provide the exact code, but I hope this example is sufficient.

class BaseTableVersion{
   Long getId();
   void setId(Long id);
   String getVersion();
   void setVersion(String version);
   TableType getTableType();
}

class TableVersion extends BaseTableVersion{
   Long getVersionNumber();
   void setVersionNumber(Long versionNumber);
}


//this class needs to exists in some capacity. I can't make it inherit a class as it is now because
//it already inherits another class (which I can't show or change) and java doesn't support multiple. 
// inheritence. I can add members or change methods 
class TableVersionRules{
    void create(TableVersion tableVersion){
        //do stuff
    }

    void versionChanged(TableVersion tableVersion){
          //do stuff
    }
}

//this class doesnt need to exists, its just to hopefully illustrate what i want.
class BaseTableVersionRules<B extends BaseTableVersion>{
    void create(B tableVersion){
        //do stuff
        //call TableVersionRules.create(tableVersion) somehow
    }

    void versionChanged(B tableVersion){
          //do stuff
        //call TableVersionRules.versionChanged(tableVersion) somehow
    }
}

So, conceptually what I want is to somehow link TableVersionRules and BaseTableVersionRules such that when TableVersionRules.versionChanged is called, it will call BaseTableVersionRules.versionChanged first, and then do what is in TableVersionRules.versionChanged. What design pattern could I use for this, or does this just defy polymorphism?

Answer 1

It looks like an inheritance with child class calling parent class using "super" keyword. Something like that:

class TableVersionRules extends BaseTableVersionRules {
  void versionChanged(...) {
    super.versionChanged(...);
    // Do some more stuff here.
  }
}

"Super" will call the implementation from parent class, and then you can still add some more code here.

Does it make sense?

UPDATE: If you can't use "extends" since class already extends something else, try using a local field:

class TableVersionRules extends SomeOtherStuffThatNeedsToBeThere {
  private final BaseTableVersionRules delegate;

  void versionChanged(...) {
    delegate.versionChanged(...);
    // Do some more stuff here.
  }
}