如何用BlazeDS前后台数据交互

续上一篇文章如何用BlazeDS更改图片 之后，本篇文章介绍了如何在后台构建数据，并传送到前台。一般来讲有两种方式：构造XML数据，传送到前台后，通过XMLSerializer反序列化到DataBox中；后台构建Java对象，通过BlazeDS传送到前台后，映射成TWaver Flex的数据对象，然后直接添加到DataBox中。这里只介绍后面这种RemoteObject的方式，XML的方式将在后续文章中介绍。

先来看看技术点：BlazeDS的序列化机制。Flex的类只要指定[RemoteClass(alias="common.CNode")]，或者registerClassAlias(“common.CNode”, CNode)，就可以将Java类映射成Flex类。public的变量，或者有get和set方法的变量都将自动映射。但有些类型的变量映射就会出问题，比如Point：java和flex的Point类型无法自动映射。因此，自己控制哪些变量序列化，如何序列化相当关键。更多资料请参考官方文档。

Serializing between ActionScript and Java
Explicitly mapping ActionScript and Java objects

下面介绍如何自定义序列化
1. 创建Java数据类，这里将TWaver Flex的Data、Element和Node分开创建了，以便复用。其他数据类型，比如Link，Group等，大家可以类似创建，可以自己实现试试，练练手。

 

 

public class CData implements Externalizable {
    ...
    public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException {
        this.setIcon((String)in.readObject());
        this.setName((String)in.readObject());
        this.setToolTip((String)in.readObject());
    }

    public void writeExternal(ObjectOutput out) throws IOException {
        out.writeObject(this.getIcon());
        out.writeObject(this.getName());
        out.writeObject(this.getToolTip());
    }
}

public class CElememt extends CData implements Externalizable {
    ...
    public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException {
        super.readExternal(in);
        this.setLayerID(in.readObject());
    }

    public void writeExternal(ObjectOutput out) throws IOException {
        super.writeExternal(out);
        out.writeObject(this.getLayerID());
    }
}

public class CNode extends CElememt implements Externalizable {
    ...
    public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException {
        super.readExternal(in);

        this.setImage((String)in.readObject());
        this.setX(in.readDouble());
        this.setY(in.readDouble());
        this.setWidth(in.readDouble());
        this.setHeight(in.readDouble());
    }

    public void writeExternal(ObjectOutput out) throws IOException {
        super.writeExternal(out);

        out.writeObject(this.getImage());
        out.writeDouble(this.getX());
        out.writeDouble(this.getY());
        out.writeDouble(this.getWidth());
        out.writeDouble(this.getHeight());
    }
}

2. 生成数据，很简单，一个循环模拟了一些数据

public static CNode[] getNodes(){
    CNode[] result = new CNode[4];
    for(int i=0; i<result.length; i++){
        CNode node = new CNode();
        node.setName("Node"+i);
        node.setX(50*i);
        node.setY(50*i);
        node.setToolTip("toolTip"+i);
        node.setIcon("group_icon");
        node.setImage("group_image");
        node.setLayerID("Layer"+i);
        result[i] = node;
    }
    return result;
}

3. 创建Flex数据类，这里注意保持和Java序列化的顺序一致

 

public class CNode extends twaver.Node implements IExternalizable {
    ...
    public function readExternal(input:IDataInput):void {
        //Data
         super.icon = input.readObject() as String;
        super.name = input.readObject() as String;
        super.toolTip = input.readObject() as String;
        //parent

        //Element
        super.layerID = input.readObject();

        //Node
        super.image = input.readObject() as String;
        super.location = new Point(input.readDouble(), input.readDouble());
        var width:Number = input.readDouble();
        if(width >= 0){
            super.width = width;
        }
        var height:Number = input.readDouble();
        if(height >= 0){
            super.height = height;
        }
    }

    public function writeExternal(output:IDataOutput):void {
        //Data
        output.writeObject(super.icon);
        output.writeObject(super.name);
        output.writeObject(super.toolTip);
        //parent

        //Element
        output.writeObject(super.layerID);

        //Node
        output.writeObject(super.image);
        output.writeDouble(super.x);
        output.writeDouble(super.y);
        output.writeDouble(super.width);
        output.writeDouble(super.height);
    }
}

4. 加载数据，用上一篇文章封装好的方法一个调用就OK了，另外别忘了用registerClassAlias给Flex类指定别名

 

registerClassAlias("common.CNode", CNode);

private function loadDatas(event:MouseEvent):void {
    RemoteObjectUtil.invoke("DataUtil", "getNodes", function(result:Object):void{
        var nodes:Array = result as Array;
        for each(var node:CNode in nodes){
            box.add(node);
        }
    });
}

如需源码请留言