JHotDraw的IO问题

您好！请教一个问题：jhotdraw7.6中samples中draw实例中有个file菜单中有个“open”的功能，可以根据xml文件生成图形，请问这个功能的代码在哪儿？谢谢

 

 

你好，我用的是7.5的版本，我想应该是一样的。

实现机制：
draw的存储接口是DOMStorable，负责drawing的IO操作；所有继承或实现该接口的子类都必须实现了read和write方法，即实现具体类的读入和写出责任。AbstractAttributedFigure和Drawing都继承该接口。

读取文件的顺序为：

1. openAction读入文件，调用DrawView的read方法读取该文件；
2. DrawView中维护多个inputFormat，每个inputFormat负责读取特定的Figure；当调用read方法时，DrawView尝试让所有的inputFormat读取该文件，但只要有一个inputFormat读取成功就停止。

至于DrawView装载了多少InputFromat，可以参考 org.jhotdraw.samples.draw.DrawView.createDrawing()：

 

 

 

 protected Drawing createDrawing() {
        Drawing drawing = new QuadTreeDrawing();
        DOMStorableInputOutputFormat ioFormat =
                new DOMStorableInputOutputFormat(new DrawFigureFactory());
        
        drawing.addInputFormat(ioFormat);
        ImageFigure prototype = new ImageFigure();
        drawing.addInputFormat(new ImageInputFormat(prototype));
        drawing.addInputFormat(new TextInputFormat(new TextFigure()));
        TextAreaFigure taf = new TextAreaFigure();
        taf.setBounds(new Point2D.Double(10,10), new Point2D.Double(60,40));
        drawing.addInputFormat(new TextInputFormat(taf));
        
        drawing.addOutputFormat(ioFormat);
        drawing.addOutputFormat(new ImageOutputFormat());
        return drawing;
    }

 


参考org.jhotdraw.draw.LineConnectionFigure对write()和read()的实现：

 

//org.jhotdraw.draw.LineConnectionFigure.read
public void read(DOMInput in) throws IOException {
        readAttributes(in);
        readLiner(in);

        // Note: Points must be read after Liner, because Liner influences
        // the location of the points.
        readPoints(in);
    }

//org.jhotdraw.draw.AbstractAttributedFigure.readAttributes
 protected void readAttributes(DOMInput in) throws IOException {
        if (in.getElementCount("a") > 0) {
            in.openElement("a");
            for (int i=in.getElementCount() - 1; i >= 0; i-- ) {
                in.openElement(i);
                String name = in.getTagName();
                Object value = in.readObject();
                AttributeKey key = getAttributeKey(name);
                if (key != null && key.isAssignable(value)) {
                    if (forbiddenAttributes == null
                            || ! forbiddenAttributes.contains(key)) {
                        set(key, value);
                    }
                }
                in.closeElement();
            }
            in.closeElement();
        }
    }




 protected void readLiner(DOMInput in) throws IOException {
        if (in.getElementCount("liner") > 0) {
            in.openElement("liner");
            liner = (Liner) in.readObject();
            in.closeElement();
        } else {
            liner = null;
        }

    }


//org.jhotdraw.draw.LineConnectionFigure.readPoints
 protected void readPoints(DOMInput in) throws IOException {
        super.readPoints(in);
        in.openElement("startConnector");
        setStartConnector((Connector) in.readObject());
        in.closeElement();
        in.openElement("endConnector");
        setEndConnector((Connector) in.readObject());
        in.closeElement();
    }

 

读入机制参见：
org.jhotdraw.app.action.file.OpenFileAction#openViewFromURI() line 105
org.jhotdraw.samples.draw.DrawView#read()
org.jhotdraw.xml.DOMFactory