如何向上转换和使用子特定方法

Question

我遇到以下问题：

//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() 方法的最简洁方法是什么？

更新1：
Cyber​​nate，如果您可以控制 DepartmentType & ，您的方法似乎是最合乎逻辑的。 组织类型。不幸的是，这些对象是由 xmlbeans 从 XML 模式生成的。就我而言，我可以重新设计架构，以便两种类型具有共同的基础。

但是如果我无法控制架构怎么办？我如何实现基本想法？

Answer 1

我建议您让这两个类实现一个通用接口，然后强制转换为该接口。我看不出您当前的转换会产生任何效果...

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。
然后

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

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，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 将如何处理它。

<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，这是一种解决方法（黑客？），但您可以使用 Commons BeanUtils ，只要您生成的类遵循JavaBean 命名约定。如果这些对象被频繁传递，您可以创建一个包装类以使调用更加具体。

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......除了太多的间接。

Answer 4

使用 getName 方法创建一个接口，并且 DepartmentType 和 OrganizationType 类都实现该接口。例如 ;

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();