1

我想使用异步调用将 ArrayList 从我的服务器发送到我的客户端。调用成功，但 ArrayList 条目在此过程中重复。我完全迷路了。代码非常简单。我无法弄清楚这个错误发生的时间和地点。

共享类：

package com.posteurs.cine.shared;

import java.io.Serializable;
import java.util.ArrayList;

public class Codes extends ArrayList<Integer> implements Serializable{
private static final long serialVersionUID = 1L;
//insert 2 values
public Codes(){
    this.add(10);
    this.add(20);
}
}

接口：

package com.posteurs.cine.client;

import java.util.Set;

import com.google.gwt.user.client.rpc.RemoteService;
import com.google.gwt.user.client.rpc.RemoteServiceRelativePath;
import com.posteurs.cine.shared.Codes;

@RemoteServiceRelativePath("cineSvc")
public interface CineSvc extends RemoteService {
    public Codes getCodes();
}



package com.posteurs.cine.client;

import java.util.Set;

import com.google.gwt.user.client.rpc.AsyncCallback;
import com.posteurs.cine.shared.Codes;

public interface CineSvcAsync {
    public void getCodes(AsyncCallback<Codes> callback);
}

实施：

package com.posteurs.cine.server;

import java.util.Iterator;
import com.google.gwt.user.server.rpc.RemoteServiceServlet;
import com.posteurs.cine.client.CineSvc;
import com.posteurs.cine.shared.Codes;

public class CineSvcImpl extends RemoteServiceServlet implements CineSvc {
    private static final long serialVersionUID = 1L;

    public CineSvcImpl(){
    }

    public Codes getCodes(){
        Codes c = new Codes();
        System.out.println("On server -----------------");
        System.out.println("impl.getCodes: Codes size="+c.size());
        return c;
    }
}

来电：

package com.posteurs.cine.client;

import java.util.Iterator;
import com.google.gwt.core.client.EntryPoint;
import com.google.gwt.core.client.GWT;
import com.google.gwt.user.client.rpc.AsyncCallback;
import com.posteurs.cine.client.CineSvcAsync;
import com.posteurs.cine.shared.Codes;

public class Cine implements EntryPoint {
@Override
public void onModuleLoad() {
    CineSvcAsync svc = GWT.create(CineSvc.class);
    svc.getCodes( new AsyncCallback<Codes>() {
        public void onFailure(Throwable caught) {
            System.out.println("getCodes::callback: Async failed");
        }

        public void onSuccess(Codes result) {
            System.out.println("On client -----------------");
            System.out.println("Callback result size="+result.size());
            Iterator<Integer> it = result.iterator();
            while (it.hasNext()) 
                System.out.println(it.next());
        }
        });
}

追踪结果：

    On server -----------------
    impl.getCodes: Codes size=2
    On client -----------------
    Callback result size=4
    10
    20
    10
    20
4

1 回答 1

1

我强烈怀疑重复值是由它们在默认构造函数中的初始化引起的。默认构造函数在对象的“解组”期间在序列化中起着特殊的作用。在将序列化的字段值复制回它之前，调用它来重新创建一个“空”对象。

Try initializing the codes somewhere else. For example, you could have a init() method in the Codes class and call this method explicitly in CineSvcImpl.getCodes() after you create the instance.

于 2012-09-15T13:43:45.887 回答