Can I map descriptors to abstract base classes?

For example can I map to BaseAccount object which has an abstract method
calcPayment? thanks

Why is TopLink attempting to instantiate the Abstract Class. You should not have any data in the database that represents the AbstractClass and you would not be able to create one in attempt to persist it.
--Gordon

Similar Messages

Where to put methods in a abstract base class - subclasses system

Hi,
I’d like to ask a question on some basic design practice.
When there are methods which are common in some subclasses so I would like to “move them up” in the base abstract class, I would also like to make sure that the ADT concept of the base class itself is not broken. So I don’t want to have methods in the base class that are not general enough to be there. How to resolve this?
For example I create a base abstract class Vehicle. Then I create subclasses Plane and Tanker and realize that the startEnginge() method in them is the same and in order remove the duplicated code, I can put it in Vehicle. But later there may be Bicycle or Sled subclasses which don’t need startEngine().
In a broader sense, I would like to keep the Vehicle class as similar to the real word concept of vehicles as possible. And not evey vehicle have engine of course.
What is the solution?
Extending the class hierarchy by injecting another abstract class between the base and the subclasses? (e.g: VehicleWithEngine)
I suppose I can’t use Interfaces because I need to have the common implemenations as well.
Thanks for any comments in advance,
lemonboston
ps: I am a beginner and don't know the terminology, so if there are programming expression for the followings for example, I would be thankful if someone could help with this too:
- moving common methods up in the class hierarchy
- injecting a class in the hierarchy
- abstract base class - subclasses system

lemonboston wrote:
Hi,
I’d like to ask a question on some basic design practice.
When there are methods which are common in some subclasses so I would like to “move them up” in the base abstract class, I would also like to make sure that the ADT concept of the base class itself is not broken. So I don’t want to have methods in the base class that are not general enough to be there. How to resolve this?
You are talking about code.
Instead you need to talk about the design.
The base class represents conceptually a 'type' of something. That 'type' defines behavior. That behavior is what goes in the base class nothing else (in terms of design.)
If you have common functionality which does not fit into the definition (design) of the 'type' then you put it in another class and use (composition) that class in the sub class.
For example I create a base abstract class Vehicle. Then I create subclasses Plane and Tanker and realize that the startEnginge() method in them is the same and in order remove the duplicated code, I can put it in Vehicle. But later there may be Bicycle or Sled subclasses which don’t need startEngine(). No that is not how it works.
You have specific examples of some vehicles and then you need to manage those types generically. That is the first step.
Second step is then to determine what the exact 'type' is that you want to manage. And you use the requirements of the need to create the 'type'.
Then you look at the specific examples to determine how they will meet the needs of the type.
Thus if I have an application that must start the engines of all the vehicles in the city then I must have a vehicle class which has startEngine.
But if I have an application that manages vehicles as inventory (like a retail store) and then decide that because my examples both have engines that I might as well move it into the base class. In that case there is no 'need' for the application to manage starting vehicles. The fact that both have engines is irrelevant.
So looking back at your example you have stated functionality about your specific types but you have not stated anything about why your application needs to deal with that functionality generically.
Another way to think about it is that you do not put the shared functionality in the base because you can but rather because you must.

What is the correct way to model an abstract base class/table?

I tried to model an abstract base class/table. For the parent table I used the "Forward Engineer Strategy" "Table per child" and I set on each child table the "Super Type" to the corresponding parent table. I did this for two parent tables and five child tables. This is the result:
https://lh5.googleusercontent.com/-1La98ulWOZg/T_2Hyock5-I/AAAAAAAAAoI/00qn5ukJCpI/s678/2012-07-11
But when I engineer the logical model into a physical model, the result is not as expected:
https://lh5.googleusercontent.com/-YfF_ocUa8bY/T_2H_YSqkyI/AAAAAAAAAoc/rNEYRnTFzU4/s617/2012-07-11
First the parent table "obj" should not be created. The table is correctly omitted, but the primary key of the parent table gets created. For me this is not logical. And even worse the primary key gets created twice with the same name, which results in a DDL generation error.
And second the primary key of the "attr" table does not get merged into the primary key of the child tables. This results into two individual unique constraints although I have expected to create only one with two attributes.
Is this a bug or is there another way to model this example correctly?

chriswalsh wrote:
The installer for Silverlight installed it as a seperate volume displayed on the desktop...
Likely that's not the app itself. When you download most Mac software, you are downloading a .dmg file (a disk image) - opening that (which may happen automatically) mounts a disk image on your desktop, and then you drag the app from that disk image to your Applications folder (or an installer runs).
After copying/installing the app, you Eject the disk image, then delete the .dmg file (from your Downloads folder, probably).

Can not map .xsql to the java class name

I am using IBMWebAS V2.0 with HTTP server V1.3.3, but I having problem mapping .xsql to the java servlet class oracle.xml.xsql.XSQLservlet. class path is properly defined in the bootstap.properties file but where can I need to put the codes for proper servlet passing with proper extention.

I am using IBMWebAS V2.0 with HTTP server V1.3.3, but I having problem mapping .xsql to the java servlet class oracle.xml.xsql.XSQLservlet. class path is properly defined in the bootstap.properties file but where can I need to put the codes for proper servlet passing with proper extention.

Using base classes for common attributes

Can TopLink handle use of non-mapped abstract base classes? There are a number of fields that are common to each and every one of my domain objects which, following good OO design principals, are moved up to a common superclass. So I have:
public abstract class AbstractDomainObject
private Integer id;
private Date dateCreated;
private Integer creatorId;
private Date dateModified;
private Integer modifierId;
// ... appropriate attribute accessors
Then a concrete class which gets mappped in Workbench:
public class Address
extends AbstractDomainObject
... specific attributes
I tried mapping all the specific attributes explicitly defined in the Address class and then using "Map Inherited Fields > To SuperClass" in Workbench. However, when attempting to test my mappings in the SessionConsole, only the attributes explicitly defined on Address are present in the SELECT clause.
Can what I am trying be done? If so, how?

Steve,
What you are trying to do is very common and the process you described is exactly how map the class. I will summarize a couple of points for mapping this scenario.
1. You only need to import Address in and map it. If AbstractDomainObject is imported into the Mapping Workbench make sure that it is disabled. The abstract class is only required on the project's CLASSPATH.
2. You should not enable inheritance for the Address class. Inheritance is for situations where the abstract base class has its own independent table. I am assuming that your Address class has its own table that contains fields for all of the attributes it needs along with those of the abstract base class.
Assuming these conditions are met then TopLink will work fine with you Address class just as if it had all of the inherited attributes directly.
If you are still having trouble take a look through your generated project (XML or Java) to ensure that mappings exist in Address for All attributes. If the project looks good then I am at a loss. Customers have been using this pattern of use for over 5 years with TopLink and Java inheritance.
Cheers,
Doug

Abstract/ concrete class questions/problems

I am new to java and working on a abstract problem. I'm getting several errors. Here is the code I have so far for the abstract class. I commented out the super and it compiles but I'm not sure if it correct. I'm suppose to create a abstract base class Animal. Single constructor requires String to indicate type of animal which then is stored in an instance variable. I also have to add a few methods (describe(), move(), etc).
public abstract class Animal
     public Animal(String type)
          //super(type);
     public abstract String describe();
     public abstract String sound();
     public abstract String sleep();
     public abstract String move();
}

thanks for the replies. I modified my code but I have a few more errors I can't figure out. Can you browse the code and help point me in the right direction.
Here are the errors I get
cannot find symbol
symbol : constructor Cat(java.lang.String,java.lang.String)
location: class Cat
cannot find symbol
symbol : constructor Robin(java.lang.String)
location: class Robin
abstract base class:
public abstract class Animal
     String type;
     public Animal(String type)
       this.type = type;
     public abstract String describe();
     public abstract String sound();
     public abstract String sleep();
     public abstract String move();
}concrete class
public class Cat extends Animal
     private String name;
     protected String breed;
     public Cat()
       super("Cat");
     public String describe()
          return new String(",a breed of Cat called");
     public String sound()
          return new String("Meow");
     public String sleep()
          return new String("Kitty is having purfect dreams!");
     public String move()
          return new String("This little Kitty moves fast!");
}another abstract class
public abstract class Bird extends Animal
     protected String breed;
     public Bird()
       super("Bird");
     public abstract String move();
}here is the abstract test program itself
public class AbstractTest
     public static void main(String[] args)
          Cat cat = new Cat("Kitty", "Angora");
          Robin bird = new Robin("Rockin");
          System.out.println("Form the cat:   ");
          System.out.print("This is:     "); cat.describe();
          System.out.print("Sound:       "); cat.sound();
          System.out.print("Sleeping:    "); cat.sleep();
          System.out.print("Moving:      "); cat.move();
          System.out.println("\n");
          System.out.println("For the robin:     "); bird.describe();
          System.out.print("This is:             "); bird.sound();
          System.out.print("Sound:               "); bird.sleep();
          System.out.print("Moving:              "); bird.move();
          System.out.print("\n");
          System.out.println("nEnd of program.");
}

Base classes with Collection attributes

I have a question. Suppose I have a base class A, an abstract base class
to be exact, and subclasses B and C. Assume A has an attribute of
Collection type, let's call it collectionImpl. Now I would like subclasses
B and C to be able to have elements of different types along the lines of
what I've outlined below.
Strictly speaking, class A wouldn't have to be PC, since I primarily care
of B and C but I wanted to show the structure.
<class name="A" persistence-capable-superclass="A">
<field name="collectionImpl">
<collection element type="someType"/>
</field>
</class>
<class name="B" persistence-capable-superclass="A">
<field name="collectionImpl">
<collection element type="someOtherType"/>
</field>
</class>
So, how would one express this?
Scott

Understood. Now for bit more clarification. Given my earlier example, what
if classes A, B and C implement the java.util.Collection interface. Does
Kodo have in issue with that? I know Kodo has this ProxyCollection stuff
but I don't really want to do that, nor do I think I really need to given
what I'm trying to accomplish.
The issue I'm having now is that the Kodo Enhancer is complaining that no
element-type is declared when I have an attribute of class type B for
example (implementing java.util.Collection) even though an element type is
declared for the that actual Collection object held in the base class of B
(A).
<class name="A" requires-extent="false">
<field name="impl">
<collection element-type="SomeType"/>
<extension vendor-name="kodo" key="ordered" value="true"/>
</field>
</class>
<class name="B" persistence-capable-superclass="A"
requires-extent="false"/>
Class "A" extends java.util.AbstractSet, impl is an instance of
java.util.Collection.
All this was working quite well until I made some updates recently
although the basic implementation is the same. Logically I don't know what
I might have done to cause the new error message.
I'm using v2.5.2 BTW.
Scott
Stephen Kim wrote:
The one thing to note is that if you do not make A persistent capable,
you cannot persist fields -declared- in A or query starting from A.
Scott A. Leschke wrote:
Can I acheive the same effect by making A be non-PC and provide a abstract
protected method that will be used by a to access the collection
implemented in the sub-classes as you suggest (ie. Collection
getCollectionImpl())?
Steve Kim
[email protected]
SolarMetric Inc.
http://www.solarmetric.com

12.4 beta: private copy constructor in base class required to be called from temporary reference when -g option used

Hi,
We've got an abstract base class (StringBase) which various types of strings inherit from. The copy constructor for this base class is private, since we don't want to allow copying when this class shouldn't be directly instantiated. A number of our methods take specify the base class as a reference, but take a derived class temporary as a default argument (see code appended).
This worked fine in 12.3, but in 12.4 beta, this now says:
   Error: StringBase::StringBase(const StringBase&) is not accessible from __dflt_argA().
This works fine in clang and gcc, and indeed, this GNU document says it was a bug which was fixed in gcc 4.3.0:
    Copy constructor access check while initializing a reference
which references http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#391
It only appears to error when the "-g" option is used, however, which doesn't seem right, and compiles fine if the "-g" option is removed, which makes me think it's a bug. Presumably the optimizer is eliding the copy when not using -g, but it's left in for debug mode, causing the compile error?
Many thanks,
Jonathan.
$ clang++ -std=c++11 defaultarg.cpp
$ g++ -std=c++11 defaultarg.cpp
$ /opt/SolarisStudio12.4-beta_mar14-solaris-x86/bin/CC -c defaultarg.cpp
$ /opt/SolarisStudio12.4-beta_mar14-solaris-x86/bin/CC -g -c defaultarg.cpp
"defaultarg.cpp", line 6: Error: StringBase::StringBase(const StringBase&) is not accessible from __dflt_argA().
1 Error(s) detected.
$ cat defaultarg.cpp
#include "stringbase.h"
#include "conststring.h"
static const ConstString S_DEFAULT("default value");
void SomeMethod( const StringBase& str = S_DEFAULT )
   (void) str;
int main( void )
   SomeMethod();
$ cat stringbase.h
#ifndef STRINGBASE_H
#define STRINGBASE_H
class StringBase
protected:
   StringBase() {}
private:
   StringBase( const StringBase& );
#endif
$ cat conststring.h
#ifndef CONSTSTRING_H
#define CONSTSTRING_H
#include "stringbase.h"
class ConstString : public StringBase
public:
   ConstString() {}
   ConstString( const char* ) {}
   ConstString( const ConstString& );
#endif

Thanks for reporting the problem!
This looks like a compiler bug, I think an artifact of creating a helper function for the debugger for the default argument.
I have filed bug 18505648 for you.

BUG? Default Project Properties, Business Components: Base Classes

Is it just me, or is there a bug in the Default Project Properties Dialog when attemptiong to specify custom classes for the Business Component Base Classes.
I have extended EntityCache and can successfully specify it as a base class via the Project Properties dialog, but in Default Project Properties, I get an error stating: "The selected class is not a valid superclass. Either is does not implement the interface oracle.jbo.server.EntityCache or it has an invalid modifier".
FYI: My custom library has been added to the Default Project Properties->Libraries.
Any help?

Does it work if you use the:
Tools | Preferences... | Business Components > Base Classes panel instead?

Abstract Graphics class ???ques???

Referring to the abstract methods within this class such as drawPolyline and drawPolygon, etc . . . it says in the documentation for Class Graphics:
"The Graphics class is the abstract base class for all graphics contexts that allow an application to draw onto components that are realized on various devices, as well as onto off-screen images."
There are no sub-class method overrides for drawPolyline and drawPolygon, for example, except for those in subclass Class DebugGraphics, which in turn call Graphics.drawPolyline and Graphics.drawPolygon - for example - at the end of the method implimentation anyway.
And besides, DebugGraphics is a swing class, and I would not be importing it in a strictly AWT application anyway.
So where is the actual code for these methods is what I am wondering?
Thanks;
~Bill

The Graphics class is subclassed in JVM specific classes since rendering
graphics on different machines is going to be done differently (this
was discussed recently). So to use these methods find a suitable object
(like an image already loaded) and call getGraphics on it. This will
return a Graphics object cast from the JVM specific graphics subclass...
Steve

How to call a method of a base class if the base class is abstract...

This is my sample code>>>>
abstract class b {
     public void display() {
          System.out.println("I am in Base Class");
class test extends b {
     public static void main(String[] args) {
          test obj = new test();
          obj.display();
     public void display() {
          System.out.println("I am in Derived Class");
I want to call base class version of display with derived class object.........is it possible....

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Enough with the friggin' zombie threads already!

Can a derived class catch base class object

can a derived class object catch a base class object
e-g if i have a class
class Test {
// code
}and
class Test2 extends Test {
}and lets say there is a method that return an object of Test (base class), so is it possible to write
Test2 t=getTestObj(); // i-e subclass holding base class objectif its not.. how can we do so? so that derived class should hold base class object....

sorry..
here is how it goes
i have a function a class
public Test getObj() {
// code
}The constraint is that i cant change the implementation of this above function.
Now when i call this function, it returns me a Test object. But i cant do
Test t=getObj();because the Test class is written purely in java whereas i want to use write a new Test class that implements the same functionality [using the above given function] in JNI.
so what i did, i created a new package [nativ] and created a class "Test" in that. But since i have to use the function that returns me Test and not "nativ.Test", so what i did, i inherited nativ.Test from "Test" so that the object might resolve the reference.
So this is it.. that i cant modify the function and i need some way to do it.. plz reply

Can I create the object of an protected inner class of a Base class in to t

Dear All,
Can I create the object of an protected inner class of a Base class in to the subclass ?
e.g.
public class Base{
     protected class Inner {};
Public class Sub extends Base{
     Public Inner amethod (){
          Return new Inner(); //here I get an exception as
                            //Inner has protected access
}Regards,
Ishan

@Op. The code that you posted isn't close to compiling. Java is case sensitive. It should be public and not Public, and return instead of Return.
Kaj

Set fields of derived class in base class constructor via reflection?

Does the Java Language Specification explicitly allow setting of fields of a derived class from within the base class' constructor via reflection? The following test case runs green, but I would really like to know if this Java code is compatible among different VM implementations.
Many thanks for your feedback!
Norman
public class DerivedClassReflectionWorksInBaseClassConstructorTest extends TestCase {
abstract static class A {
    A() {
        try {
            getClass().getDeclaredField("x").setInt(this, 42);
        } catch (Exception e) {
            throw new RuntimeException(e);
static class B extends A {
    int x;
    B() {
    B(int x) {
        this.x = x;
public void testThatItWorks() {
    assertEquals(42, new B().x);
    assertEquals(99, new B(99).x);
}

why not just put a method in the superclass that the subclasses can call to initialize the subclass member variable?In derived classes (which are plug-ins), clients can use a field annotation which provides some parameter metadata such as validators and the default value. The framework must set the default value of fields, before the class' initializer or constructors are called. If the framework would do this after derived class' initializer or constructors are called, they would be overwritten:
Framework:
public abstract class Operator {
    public abstract void initialize();
}Plug-In:
public class SomeOperator extends Operator {
    @Parameter(defaultValue="42", interval="[0,100)")
    double threshold;
    @Parameter(defaultValue="C", valueSet="A,B,C")
    String mode;
    public void setThreshold(double threshold) {this.threshold = threshold;}
    public void setMode(String mode) {this.mode = mode;}
    // called by the framework after default values have been set
    public void initialize() {
}On the other hand, the default values and other metadata are also used to create GUIs and XML I/O for the derived operator class, without having it instantiated. So we cannot use the initial instance field values for that, because we don't have an instance.

A non abstract child class must implement all pure virtual function of parent abstract class in c++

Hi,
In Indesign SDK there is a class IActionComponent having two pure virtual functions:
virtual void
UpdateActionStates(IActiveContext* ac, IActionStateList *listToUpdateGSysPoint mousePoint = kInvalidMousePoint, IPMUnknown* widget = nil) = 0;
virtual void
DoAction(IActiveContext* ac, ActionID actionID, GSysPoint mousePoint = kInvalidMousePoint, IPMUnknown* widget = nil)= 0;
But, the child class
class WIDGET_DECL CActionComponent : public IActionComponent
implements only UpdateActionStates function and not DoAction function.
There is no compilation error and the code is running fine..HOW
Can some one please explain me?

Oops!!! there is a small correction in my C++ program. The JunkMethod is being called from the constructor...like the following code.
#include <iostream.h>
#include <stdlib.h>
class Base
    public:
        Base()
            cout<<"In Base Class constructor..."<<endl;
            JunkMethod();
        void JunkMethod()
            TestAbsFunc();
        virtual void TestAbsFunc()= 0;
class TestAbstract:public Base
    public:
        TestAbstract()
            cout<<"In Extend Class constructor..."<<endl;
        void TestAbsFunc()
            cout<<"In TestAbsFunc...."<<endl;
int main()
      TestAbstract test;
      return 0;
}You can see the change in the constructor of the Base class. JunkMethod is being called, just to bluff the compiler to call the virtual method (so that it won't crib saying that abstract method cannot be called from the constructor). When Java is supporting this functionality without giving any errors, C++ gives errors when you call an abstract method from the constructor or fails to execute when I do some work around like this. Isn't it a drawback of abstract funcationality supported by C++ (I'm not sure if it's a drawback or not)
Regards,
Kalyan.

Can I map descriptors to abstract base classes?

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