如何为类型的子类实现GWT编辑器？

Question

假设我有一个像这样的对象层次结构:

帐户>网站>供应

帐户是一个实际的公司,一个网站是他们拥有的建筑物,一个供应是一个ElecSupply或一个GasSupply.供应从未实例化,理论上可能是一个抽象的阶级.

我正在使用Objectify进行持久化,并且有一个页面显示每个站点的供应列表,无论它们是否为ElecSupply或GasSupply.

现在我正在实现GWT编辑器框架,并遇到了这个多态实体的问题.如何为这样的对象实现编辑器和子编辑器集？

@Entity
public class Supply implements Serializable
{
    @Id
    protected Long id;
    @Embedded
    protected List<BillingPeriod> billingPeriods = new ArrayList<BillingPeriod>();

    public Supply()
    {

    }
// ...
}

子类:( ElecSupply有5个独特的字段,GasSupply只有一个)

@Subclass
public class ElecSupply extends Supply implements Serializable
{
    private String profile;
    private String mtc;
    private String llf;
    private String area;
    private String core;

    public ElecSupply()
    {

    }
}

---

@Subclass
public class GasSupply extends Supply implements Serializable
{
    private String mpr;

    public GasSupply()
    {

    }
// ...
}

所以我想知道是否有人对这种结构有任何经验？我曾试图为ElecSupplyand 创建单独的编辑器GasSupply,然后在编辑页面中显示或隐藏它们.

我想要做的另一种方法是使用单个编辑器(对于Supply),然后根据我们正在编辑的对象类型加载不同的子编辑器.

任何灯光都会被感激地收到.

Answer 1

我已经遇到过这种情况,我已经实现了以下解决方案:

• 首先创建一个名为AbstractSubTypeEditor的通用实用类,当您编辑其中一个子类对象时,它将激活特定的编辑器:

  import com.google.gwt.editor.client.CompositeEditor;
  import com.google.gwt.editor.client.Editor;
  import com.google.gwt.editor.client.EditorDelegate;
  import com.google.gwt.editor.client.LeafValueEditor;
  
  public abstract class AbstractSubTypeEditor<T, C extends T, E extends Editor<C>> implements CompositeEditor<T, C, E>, LeafValueEditor<T> {
          private EditorChain<C, E> chain;
          private T currentValue;
          private final E subEditor;
  
          /**
           * Construct an AbstractSubTypeEditor backed by the given sub-Editor.
           *
           * @param subEditor the sub-Editor that will be attached to the Editor
           *          hierarchy
           */
          public AbstractSubTypeEditor(E subEditor) {
                  this.subEditor = subEditor;
          }
  
          /**
           * Returns the sub-Editor that the OptionalFieldEditor was constructed
           * with.
           *
           * @return an {@link Editor} of type E
           */
          public E createEditorForTraversal() {
                  return subEditor;
          }
  
          public void flush() {
                  currentValue = chain.getValue(subEditor);
          }
  
          /**
           * Returns an empty string because there is only ever one sub-editor used.
           */
          public String getPathElement(E subEditor) {
                  return "";
          }
  
          public T getValue() {
                  return currentValue;
          }
  
          public void onPropertyChange(String... paths) {
          }
  
          public void setDelegate(EditorDelegate<T> delegate) {
          }
  
          public void setEditorChain(EditorChain<C, E> chain) {
                  this.chain = chain;
          }
  
          public void setValue(T value, boolean instanceOf) {
                  if (currentValue != null && value == null) {
                          chain.detach(subEditor);
                  }
                  currentValue = value;
                  if (value != null && instanceOf) {
                          chain.attach((C)value, subEditor);
                  }
          }
  }
  

• 现在,您可以创建一个Supply for Editor,包含两个子编辑器和两个AbstractSubTypeEditor(每个子类型一个):

  public class SupplyEditor extends Composite implements Editor<Supply> {
  
          public class ElecSupplyEditor implements Editor<ElecSupply> {
                  public final TextBox profile = new TextBox();
                  public final TextBox mtc = new TextBox();
                  public final TextBox llf = new TextBox();
                  public final TextBox area = new TextBox();
                  public final TextBox core = new TextBox();
          }
          @Ignore
          final ElecSupplyEditor elecSupplyEditor = new ElecSupplyEditor();
          @Path("")
          final AbstractSubTypeEditor<Supply, ElecSupply, ElecSupplyEditor> elecSupplyEditorWrapper = new AbstractSubTypeEditor<Supply, ElecSupply, SupplyEditor.ElecSupplyEditor>(elecSupplyEditor) {
                  @Override
                  public void setValue(final Supply value) {
                          setValue(value, value instanceof ElecSupply);
                          if (!(value instanceof ElecSupply)) {
                                  elecSupplyEditor.profile.setVisible(false);
                                  elecSupplyEditor.mtc.setVisible(false);
                                  elecSupplyEditor.llf.setVisible(false);
                                  elecSupplyEditor.area.setVisible(false);
                                  elecSupplyEditor.core.setVisible(false);
                          } else {
                                  elecSupplyEditor.profile.setVisible(true);
                                  elecSupplyEditor.mtc.setVisible(true);
                                  elecSupplyEditor.llf.setVisible(true);
                                  elecSupplyEditor.area.setVisible(true);
                                  elecSupplyEditor.core.setVisible(true);
                          }
                  }
          };
  
          public class GasSupplyEditor implements Editor<GasSupply> {
                  public final TextBox mpr = new TextBox();
          }
          @Ignore
          final GasSupplyEditor gasSupplyEditor = new GasSupplyEditor();
          @Path("")
          final AbstractSubTypeEditor<Supply, GasSupply, GasSupplyEditor> gasSupplyEditorWrapper = new AbstractSubTypeEditor<Supply, GasSupply, SupplyEditor.GasSupplyEditor>(gasSupplyEditor) {
                  @Override
                  public void setValue(final Supply value) {
                          setValue(value, value instanceof GasSupply);
                          if (!(value instanceof GasSupply)) {
                                  gasSupplyEditor.mpr.setVisible(false);
                          } else {
                                  gasSupplyEditor.mpr.setVisible(true);
                          }
                  }
          };
  
          public SupplyEditor () {
                  final VerticalPanel page = new VerticalPanel();
                  page.add(elecSupplyEditor.profile);
                  page.add(elecSupplyEditor.mtc);
                  page.add(elecSupplyEditor.llf);
                  page.add(elecSupplyEditor.area);
                  page.add(elecSupplyEditor.code);
                  page.add(gasSupplyEditor.mpr);
                  initWidget(page);
          }
  }
  

这应该根据您正在编辑的子类显示/隐藏您的字段,并将属性绑定到好字段.