继承+ RPC GWT

Question

看起来我不理解继承。我有这些类: PicaAsset，VideoAsset，它们继承自一个名为Assets的类名。这是Assets类声明：

public class Assets {
protected int book=0;
protected int fromChapter=0;
protected int toChapter=0;
protected int fromVerse=0;
protected int toVerse=0;
protected String creator=null;
protected String discription=null;
protected String source=null;
protected String title=null;
protected String duration=null;
protected String url=null;

public Assets(int book, int fromChapter, int toChapter, int fromVerse,
        int toVerse, String creator, String discription, String source,
        String title, String duration, String url) {

    this.book = book;
    this.fromChapter = fromChapter;
    this.toChapter = toChapter;
    this.fromVerse = fromVerse;
    this.toVerse = toVerse;
    this.creator = creator;
    this.discription = discription;
    this.source = source;
    this.title = title;
    this.duration = duration;
    this.url = url;
}

public Assets() {
}

public int getBook() {
    return book;
}

public void setBook(int book) {
    this.book = book;
}
public int getFromChapter() {
    return fromChapter;
}
public void setFromChapter(int fromChapter) {
    this.fromChapter = fromChapter;
}
public int getToChapter() {
    return toChapter;
}
public void setToChapter(int toChapter) {
    this.toChapter = toChapter;
}
public int getFromVerse() {
    return fromVerse;
}
public void setFromVerse(int fromVerse) {
    this.fromVerse = fromVerse;
}
public int getToVerse() {
    return toVerse;
}
public void setToVerse(int toVerse) {
    this.toVerse = toVerse;
}
public String getCreator() {
    return creator;
}
public void setCreator(String creator) {
    this.creator = creator;
}
public String getDiscription() {
    return discription;
}
public void setDiscription(String discription) {
    this.discription = discription;
}
public String getSource() {
    return source;
}
public void setSource(String source) {
    this.source = source;
}
public String getTitle() {
    return title;
}
public void setTitle(String title) {
    this.title = title;
}
public String getDuration() {
    return duration;
}
public void setDuration(String duration) {
    this.duration = duration;
}
public String getUrl() {
    return url;
}
public void setUrl(String url) {
    this.url = url;
}

PicAsset：

public class PicAsset extends Assets implements IsSerializable {

  private int picId=0;

  public PicAsset(){
  }

  public PicAsset(int picId, int book, int fromChapter, int toChapter,
        int fromVerse, int toVerse, String creator, String discription,
        String source, String title, String duration, String url) {
    super(  book,  fromChapter,  toChapter,
             fromVerse,  toVerse, creator,  discription,
            source,  title,  duration,  url);
    this.picId = picId;
  }

  public int getIdpic() {
    return picId;
  }
  public void setIdpic(int idpic) {
    this.picId = idpic;
  }
}

现在我使用一个RPC调用来使用在服务器端声明的方法来从我的数据库中获取信息，因为您可以看到该方法返回一个列表PicAsset，List。

 rpcService.getPicture((books.getSelectedIndex()+1), (chapters.getSelectedIndex()+1), new AsyncCallback<List<PicAsset>>(){
                    public void onFailure(Throwable caught) {
                        Window.alert("Can't connect to database" + books.getSelectedIndex() + chapters.getSelectedIndex());
                    }

                    public void onSuccess(List<PicAsset> result) {
                        int listSize = result.size();
                        int i;
                        int flag = 0;

                        assetPicPanel.clear();

                          Label frameTitle = new Label("Pictures");
                                for(i=0;i<listSize;i++)
                                {
                                    if(flag == 0)
                                    {
                                        assetPicPanel.add(frameTitle);
                                        flag = 1;
                                    }


                                    HorizontalPanel vPanelPic = new HorizontalPanel();

                                    System.out.print("heeeeey" +" " + result.get(i).getFromChapter());                                      
                                    Grid g = result.get(i).AssetGrid(result.get(i));

                                    vPanelPic.add(g);
                                    assetPicPanel.add(vPanelPic);
                                }
                    }
                });

现在，当我在服务器端打印..get().getFromChapter()时，它会带来正确的值。但是当我打印返回给RPC调用的值时，我得到了默认的构造函数值……而不是必须送回的东西。

这里还有服务器端的getPicture实现：

public List<PicAsset> getPicture(int book, int chapter) throws Exception

 {

    System.out.print("getPicture ok " + book +"," + chapter);
    Connection conn = null;
    PreparedStatement pstmt = null;
    ResultSet result = null;
    List<PicAsset> relevantAssets = new ArrayList<PicAsset>();
    PicAsset relAsset;


    try {
        conn = getConnection();
        pstmt = conn.prepareStatement("SELECT * FROM picasset WHERE book = ? AND fromChapter <= ? AND toChapter >= ?");

        //System.out.print("connection" + conn);
        pstmt.setInt(1, book);
        pstmt.setInt(2, chapter);
        pstmt.setInt(3, chapter);

        result = pstmt.executeQuery();

      //  System.out.print(result);
        while (result.next()) {

            //System.out.print("in while");
            relAsset = new PicAsset(result.getInt("picId"),result.getInt("book"), result.getInt("fromChapter"), result.getInt("toChapter"),result.getInt("fromVerse"),result.getInt("toVerse"),result.getString("creator"),result.getString("discription"),result.getString("source"),result.getString("title"),result.getString("duration"),result.getString("url"));
            relevantAssets.add(relAsset);

        }
    }

        catch (SQLException sqle) 
        {
            sqle.printStackTrace();
        } 
        finally
        {
            // Cleanup
            result.close();
            pstmt.close();
            conn.close();
        }

    System.out.print("In MySql get Chapter  " + relevantAssets.get(0).getFromChapter() + " " + relevantAssets.get(0).getIdpic());
    return relevantAssets;
}

Answer 1

在GWT中，使用原始数组比使用集合接口要好得多-从方法PicAsset[]返回，而不是List。这将允许您(a)解决您的问题，(b)避免将不必要的类编译为客户端代码。

请参阅gwtproject.org上的“原始类型”部分