GWT +序列化

Question

我很难尝试将我的类序列化(字面意思是3-4小时才能找到解决方案)。我将一个子类添加到现有的可序列化且正常运行的类中，然后得到以下错误消息：

 [ERROR] com.google.gwt.user.client.ui.DelegatingChangeListenerCollection is not default instantiable (it must have a zero-argument constructor or no constructors at all) and has no custom serializer. (reached via com.client.rpc.ItemRecRpc)
              [ERROR] com.google.gwt.user.client.ui.DelegatingClickListenerCollection is not default instantiable (it must have a zero-argument constructor or no constructors at all) and has no custom serializer. (reached via com.client.rpc.ItemRecRpc)
              [ERROR] com.google.gwt.user.client.ui.DelegatingFocusListenerCollection is not default instantiable (it must have a zero-argument constructor or no constructors at all) and has no custom serializer. (reached via com.client.rpc.ItemRecRpc)
              [ERROR] com.google.gwt.user.client.ui.DelegatingKeyboardListenerCollection is not default instantiable (it must have a zero-argument constructor or no constructors at all) and has no custom serializer. (reached via com.client.rpc.ItemRecRpc)
              [ERROR] com.google.gwt.view.client.ListDataProvider<T>.ListWrapper<> is not default instantiable (it must have a zero-argument constructor or no constructors at all) and has no custom serializer. (reached via com.client.rpc.ItemRecRpc)
              [ERROR] com.client.rpc.ItemRecRpc.LogCollection is not default instantiable (it must have a zero-argument constructor or no constructors at all) and has no custom serializer. (reached via com.client.rpc.ItemRecRpc)
              [ERROR] com.client.rpc.ItemRecRpc.LogCollection has no available instantiable subtypes. (reached via com.client.rpc.ItemRecRpc)
                 [ERROR]    subtype com.client.rpc.ItemRecRpc.LogCollection is not default instantiable (it must have a zero-argument constructor or no constructors at all) and has no custom serializer. (reached via com.client.rpc.ItemRecRpc)
              [ERROR] java.util.AbstractList.SubList<E> is not default instantiable (it must have a zero-argument constructor or no constructors at all) and has no custom serializer. (reached via com.client.rpc.ItemRecRpc)
              [ERROR] java.util.Collections.UnmodifiableList<T> is not default instantiable (it must have a zero-argument constructor or no constructors at all) and has no custom serializer. (reached via com.client.rpc.ItemRecRpc)
              [ERROR] java.util.Collections.UnmodifiableRandomAccessList<T> is not default instantiable (it must have a zero-argument 

我的类看起来像这样：

public class ItemRecRpc implements Serializable {

    private static final long serialVersionUID = -5828108890651522661L;
        .
        .

        private String rId;
    private LogCollection logColl;//if i comment this, no error message...

    public class LogCollection{ 

        public LogCollection(){

        }
        //public long creationTime = System.currentTimeMillis();
        //public LongVector times = new LongVector();
        //public ArrayList<Object> messages = new ArrayList<Object>();
        //public int nSkipped = 0; 
        //public int nExceptions = 0; 
        //public Exception firstException = null; 
        //public long endGcTime=0;
        public long endTime;
    }
.
.
.
}

当我注释"private LogCollection logColl“行时，它是正常的，但当我取消注释时，我再次得到错误消息。我试着使用static关键字，正如你所见，我注释了每个子类变量，但没有帮助……无论如何，如果我创建了一个新类：

public class LogCollectionRpc implements Serializable {

    public LogCollectionRpc() {
        //
    }
    public long creationTime = System.currentTimeMillis();
    public LongVector times = new LongVector();
    public ArrayList<Object> messages = new ArrayList<Object>();
    public int nSkipped = 0; // due to reaching the limit
    public int nExceptions = 0; // due to MyAppender-s
    public Exception firstException = null; // due to MyAppender-s
    public long endGcTime = 0;
    public long endTime;

}

然后尝试使用它作为我的功能类，这是可以的……但这件事真的让我头疼...

有什么想法吗？Gwt不支持子类序列化吗？还是我错过了什么。感谢你的回答。

致以最好的问候，彼得

Answer 1

此错误：

subtype com.client.rpc.ItemRecRpc.LogCollection is not default instantiable

表示默认情况下不能创建LogCollection的实例。这是真的。因为要创建LogCollection的实例，首先需要有一个ItemRecRpc的实例。将LogCollection声明为静态类应该会有所帮助。

基本上，当您希望通过gwt-rpc发送某个对象时，在此类对象中用作字段的所有类在缺省情况下都应该是可实例化的。(例如，没有特殊的技巧来创建它，只有新的和空的构造函数)。您还可以为任何类定义自定义字段序列化程序，默认情况下可以实例化这些序列化程序。