Java: Accessing Private Members

Silveira — Sat, 14 Nov 2009 07:27:14 +0000

Using reflection to change the accessibility of a private object field and access it at runtime.

import java.lang.reflect.Field;
 
class Life {
    private int meaning = 42;
}
 
class Hack {
    public static void main(String args[]){
        Life life = new Life();
        try {
            Field field = life.getClass().getDeclaredField("meaning");
            field.setAccessible(true);
            System.out.println(field.get(life));
        } catch (NoSuchFieldException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e){
            e.printStackTrace();
        }
    }
}

Output:

42

JavaFX, getting resources of inside your JAR

Silveira — Fri, 10 Apr 2009 19:51:54 +0000

Tradução: há uma versão em Português desse artigo.

For some classes like javafx.scene.image.Image is easy load an image from a external resource like:

ImageView {
    image: Image {
        url: "http://example.com/myPicture.png"
    }
}

or a resource inside your own Jar file with the __DIR__ constant:

ImageView {
    image: Image {
        url: "{__DIR__}/myPicture.png"
    }
}

But for other classes loading a internal resource (inside your own jarfile) is not so direct. For example, in the article Parsing a XML Sandwich with JavaFX I had to place the XML file in a temp directory. A more elegant way would be:

package handlexml;
 
import java.io.FileInputStream;
import javafx.data.pull.*;
import javafx.ext.swing.*;
import javafx.scene.Scene;
import javafx.stage.Stage;
 
class Resource{
    function getUrl(name:String){
        return this.getClass().getResource(name);
    }
 
    function getStream(name:String){
        return this.getClass().getResourceAsStream(name);
    }
}
 
var list = SwingList { width: 600, height: 300}
 
var myparser = PullParser {
    documentType: PullParser.XML;
    onEvent: function (e: Event) {
        var item = SwingListItem {text: "event {e}"};
        insert item into list.items;
    }
    input: Resource{}.getStream("my.xml");
}
myparser.parse();
 
Stage {
    title: "Map"
    scene: Scene {
        content: list
    }
}

With a simple XML file called my.xml inside your package.

 version="1.0" encoding="UTF-8"?>
 sesame="true">
   />
   />
    type="chedar"/>
   />
   />
>

And we get the same result as before, but all files inside our Jars.

References:

Acessing Resources Inside of JAR Files

JavaFX Core Tutorial

this

Silveira Neto » getclass

Java: Accessing Private Members

JavaFX, getting resources of inside your JAR