在super（）构造函数中获取子类名称

Question

I have two Java classes TeradataTable and RdbmsTable -

Useful part of RdbmsTable.java

public class RdbmsTable {

    public RdbmsTable(String uri, String type) {
       this.uri = uri;
       this.type = type;
    } 

Useful part of TeradataTable.java

public class TeradataTable extends RdbmsTable {

    public TeradataTable(String uri) {
        super(uri, "TERADATATABLE");
    }

I need to set className in upper case in super() constructor. I don't want to use hardcoded string.

I can't use this.getClass().getSimpleName().toUpperCase(); in super() .

Is there something wring design wise?

Answer 1

If you need that name in the RdbmsTable constructor, use this.getClass().getSimpleName().toUpperCase() there (rather than super ):

public RdbmsTable(String uri) {
   this.uri = uri;
   this.type = this.getClass().getSimpleName().toUpperCase();
}

getClass always gives you the instance's actual class , regardless of where you call it from. So in RdbmsTable above, this.getClass() will return the Class instance for whatever class the instance actually is. If it's a TeradataTable instance, this.getClass() will return a reference to the Class for TeradataTable (not RdbmsTable ).

Live Example :

class Example
{
    public static void main (String[] args) throws java.lang.Exception
    {
        new TeradataTable("foo");
    }
}

class RdbmsTable {
    public RdbmsTable(String uri) {
       System.out.println(this.getClass().getSimpleName().toUpperCase());
    } 

}

class TeradataTable extends RdbmsTable {
    public TeradataTable(String uri) {
        super(uri);
    }
}

Output:

TERADATATABLE

But I'd think it would be better to use an annotation or some such to parameterize this, in case you need to use a name that isn't an exact match for the class name at some point.

Answer 2

Would that work for you?

public class TeradataTable extends RdbmsTable {

    public TeradataTable(String uri) {
        super(uri, TeradataTable.class.getSimpleName().toUpperCase());
    }

• it does not need 'this'
• it is just the static version of your approach
• it still updates if you refactor your class names
• you can keep the other code as is