如何向上转换和使用特定于儿童的方法

Question

我有以下问题：

//class XmlObject is part of org.apache.xmlbeans
public class DepartmentType extends XmlObject; // getName method is defined in this class
public class OrganizatiopnType extends XmlObject; // getName method is defined in this class

XmlObject department = null;
if (a == 1)
    department = (DepartmentType) order.getDepartment(); // returns DepartmentType
else
    department = (OrganizationType) order.getOrganization(); // returns OrganizationType

department.getName(); // throws cannot find symbol
// ... and do some other complex stuff using methods which are defined in both classes ...

调用 getName() 方法最简洁的方法是什么？

更新 1：
Cyber​​nate，如果您可以控制DepartmentType 和OrganizationType，您的方法似乎是最合乎逻辑的。不幸的是，这些对象是由 xmlbeans 从 XML 模式生成的。在我的例子中，我可以重新设计模式，让两种类型都有共同的基础。

但是，如果我无法控制架构怎么办。我如何才能实现基本思想？

Answer 1

我建议你让两个类都实现一个通用接口，然后转换为那个接口。我看不出你目前的演员阵容有什么影响......

public interface NamedElement
{
    String getName();
}

...

NamedElement department = a == 1 ? order.getDepartment() : 
                                   order.getOrganisation();
String name = department.getName();

当然，这是假设您可以控制 DepartmentType 和 OrganizationType 代码。

Answer 2

注意：这是当前类层次结构的替代方案。

定义一个名为 UnitTypeBase 的中间类，它从 XmlObject 扩展。 像

public class UnitTypeBase extends XmlObject{
 public String getName(){
  //Some implementaition or you can mark it as abstract
 }
}

然后派生 *DepartmentType 和 OrganizationType* 从 UnitTypeBase

//class XmlObject is part of org.apache.xmlbeans 
public class DepartmentType extends UnitTypeBase; // getName method is defined in this class 
public class OrganizatiopnType extends UnitTypeBase; // getName method is defined in this class  
UnitTypeBase department = null; 
if (a == 1)     
  department = (DepartmentType) order.getDepartment(); // returns DepartmentType 
else     
     department = (OrganizationType) order.getOrganization(); // returns OrganizationType  
department.getName(); 
     // ... and do some other complex stuff using methods which are defined in both classes ... 

Answer 3

如果您可以控制架构，则可以定义一个基本抽象类型，您的其他类型可以从中扩展。我自己没有尝试过，所以我不确定 XmlBeans 会如何处理它。

<complexType name="NamedEntity" abstract="true">
    <sequence>
        <element name="name" type="string"/>
    </sequence>
</complexType>

<complexType name="DepartmentType">
    <complexContent>
        <extension base="NamedEntity">
            <sequence>
                <element name="whatever"/>
            </sequence>
        </extension>
    </complexContent>
</complexType>

否则，这是一种变通方法（hack？），但您可以使用Commons BeanUtils，前提是您生成的类遵循 JavaBean 命名约定。如果这些对象被大量传递，您可以创建一个包装类来使调用更加具体。

public class Department {
    XmlObject obj;

    public Department(XmlObject obj){
        if(!obj instanceof DepartmentType || !obj instanceof OrganizatiopnType){
            throw new IllegalArgumentException();
        }
        this.obj = obj;
    }

    public String getName(){
        return (String)PropertyUtils.getProperty(obj, "name");
    }
}

任何问题都可以通过另一层间接解决......除了太多间接。

Answer 4

使用方法getName 创建一个接口，DepartmentType 和OrganizationType 类都实现了这个接口。比如;

public class IName {
   public void getName();
}

public class DepartmentType extends XmlObject implements IName {}

public class OrganizationType extends XmlObject implements IName {}

IName department = null;
if (a==1)
  department = order.getDepartment();
else
 department = order.getOrganization();
String name = department.getName();