Question

假设我有一个像这样的对象层次结构：

帐户＆gt;网站＆gt;供应

帐户是实际公司，网站是他们拥有的建筑物，而供应商是ElecSupply或GasSupply。供给从未实例化，理论上可能是一个抽象的类。

我正在使用Objectify进行持久性，并且有一个页面显示每个网站的耗材列表，无论它们是ElecSupply还是GasSupply。

现在我正在实现GWT Editor Framework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一组子编辑器？

@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？我尝试为ElecSupply和GasSupply制作单独的编辑器，然后在编辑页面中显示或隐藏它们。

我考虑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。

任何光线都会被感激地接受。

Answer 1

我已经遇到过这种情况，我已经实施了以下解决方案：

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。

Answer 2

您可以让您的SupplyEditor实施ValueAwareEditor<Supply>。

这样，编辑器框架会传递setValue(Supply supply)中正在编辑的实际值; 在setValue(Supply supply)的实施中，您可以检查供应类型并选择显示/隐藏任何其他相关字段。

如何为类型的子类实现GWT编辑器？

2 个答案: