Sunday, November 30, 2008

Set up blazeds on tomcat with eclipse for FLEX .

Alright,

This is a quick post on how to setup your first blazeds environment for eclipse on your existing tomcat installation.

By the end of this short tutorial you will be able to have a simple flex page that can call your remote object using blazeds on tomcat.

Note:I use eclipse 3.3 with the flex builder plugin installed. Steps will probably remain the same for flex builder with wtp installed too.

1.Download blazeds from adobe.com. Extract the blazeds.war file onto a folder.I will tell you how to use this in a few steps.

2.Create your tomcat server on eclipse. If you had not added your existing tomcat as a runtime in eclipse , this is a good time to do so.

3.Create a new "Dynamic web project " on eclipse. Call it BlazeAllinOne. Now go back to the folder where you had extracted blazeds.war and copy the META-INF and WEB-INF folders from there to the "Webcontent" folder that eclipse had created in the project. The WEB-INF should include lib,flex,classes,src folders. And most importantly the new web.xml file.

4.Right click on the project and change the build path such that the java classes will be compiled into the classes folder.RightClick->properties->java build path->Source tab.


NOtice the "Default output folder" entry that is pointing to the classes folder we copied from blazeds.war

5.Open the services-config.xml file within WEB-INF/Flex folder and change entries from this

endpoint url="http://{host}:{port}/{context-root}/messagebroker/amf" class="flex.messaging.endpoints.AMFEndpoint"

TO

endpoint url="http://localhost:8080/BlazeAllinOne/messagebroker/amf" class="flex.messaging.endpoints.AMFEndpoint"

Note BlazeAllinOne was how my project was deployed. Note.Do not WebContent or anythng after your project's name.

6.Build your project, if you have not set Build-Automatically on the project menu.By this point you have generic blazeds-tomcat setup that can invoke remote objects.

Verify your setup by testing if the amf links are active . Paste the endpoint url you changed on services.xml onto your browser. something like this http://localhost:8080/BlazeAllinOne/messagebroker/amf should return you a blank page and not a 404 or 500 error.

If you get 404 error,Somethings wrong!

Now some clarifications. Why did I create a dynamic web project and copy my blazeds files? Because only of its a DWP , eclipse will deploy it in tomcat container. If you had created a simple java project and pointed to your blazeds WEB-INF folder, eclpse will not deploy the app, everytime you start the server through eclipse.

7.Let us now see how we tie up flex to the server side environment we just created..

8.Create a simple java classes on your blaze-server project .Something like this

package test;

public class tester {
public String getData() {
return "hi";
}
}

9.Build the project again. The test.tester.class file should now be generated within the WEB-INF/classes folder.

10.Open your remoting-config.xml file and create a new destination pointing to the new class.
the entry goes like this

<destination id="testremote">
<properties>
<source>test.tester</source>
</properties>
</destination>

Now Lets create the client

11.NewProject-Flex-select J2ee in application server type.Unselect "Create combined flex/java src folder".Click next

12.Deselect the "Use default location for LCDS " and enter the following.

RootFolder :{youreclipseworkspace}\BlazeAllinOne\WebContent\
Root URL:http://localhost:8080/BlazeAllinOne/
Context_Root:BlazeAllinOne/. Click finish

13.Create a simple mxml and paste this code

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute">
<mx:RemoteObject id="test" destination="testremote">

</mx:RemoteObject>
<mx:Script>
<![CDATA[
import mx.controls.Alert;
import mx.rpc.events.FaultEvent;
import mx.rpc.events.ResultEvent;
private function getData():void {
test.addEventListener(ResultEvent.RESULT,resultHandler);
test.addEventListener(FaultEvent.FAULT,faultHandler);
test.getData();
}
private function resultHandler(eve:ResultEvent):void{
Alert.show(eve.message.body.toString());
}
private function faultHandler(eve:FaultEvent):void{
Alert.show(eve.message.toString());
}

]]>
</mx:Script>
<mx:Button label="click" click="getData()">

</mx:Button>
</mx:Application>

Note:The remote object destination I use is testremote.The one I created in remoting-config.xml file.

14.Build all and restart the server if its neccessary. RIght click on your mxml and select "Run as Flex application"

15.Click on the button. You should be getting a pleasant "hi" from your server setup :-)

16.Note that you can setup break points on flex and java and debug them parallely.

There you go. You have the power of flex,blazeds,tomcat on your hands.

Make the world a better place :-)

Hope it helps!


Bookmark and Share

Tuesday, November 25, 2008

What Adobe Air Should be able to do but does'nt!

Alright, after working with adobe air for sometime, I find myself longing for the following features.

 

1.Ability to execute system processes -  I do understand that this poses a security riskl, but what the hell.? The user is installing AIR as an administrator after all. Adobe should learn from SUN here and do what java does best. Even though java is meant to be cross platform, it does provide developers with options like JNI API to use native code whenever required.

 

2.Ability to add options to context menu on file/folder icons – Remember how svn or winzip can add multiple options to context menus that comes when you right click on a file?? This is something I would really love to have in my air application . And no its not there! Cant believe they missed it.

 

3.AIR can have an API to parse EXCEL/WORD files – What I am trying to say is something like apache POI that helps AIR apps to read and write binary data from files in the files ystem and make sense out of it. Even a bridge between Apache POI and air might do the trick

 

4.Auto Sync API – Synching the built in sqlite database can be simpler. Some kind of an auto sync api to update the local db will be very helpful .Right now its just possible to detect a change in network connectivity and you are on your own to do what is to be done.

 

That’s it for now. I will add as soon as I find myself wanting more. Still love AIR/FLEX though! J

 

 

 




Bookmark and Share

Wednesday, November 19, 2008

Flex Specific security considerations

When it comes to security there is no end to what one can do , but the basic techniques that an attacker remains the same. In case of a RIA built with flex, there are a

few important and unique considerations.

 

  • It’s very very simple to decompile a Flex or Flash file. The file format is public and many decompilers are already in place. The Same can be said about javascript too, but the thing is that with flex based RIA’s a lot of  context and logic is saved on the client side. If you are a fan of saving sensitive data on client side,watch out! Its too easy to know what you are doing on the client.
  • It’s equally easy to monitor requests and results from a Flex app to and from the server. This and the above make it a breeze to get the URI’s and expected parameters for your PHP scripts.Softwarre like ETHEREAL do a great job in finding out what is being sent and received.
  • Most Flex/PHP/JSP architected applications will expect and return clean, simple XML data. This data can be parsed easily to see if any security holes can be exploited.Thats why you will have to seriously consider the binary protocol AMF and start using its implementation in the form of Blazeds.LCDS or AMFPHP

 

Hope it helps!





Bookmark and Share

Tuesday, November 18, 2008

How to test if an object is of a given type?

When dealing with typeCasting its essential to test if the objects are compatible before having a
typecast statement.Forgetting to do this results in fragile code that might throw a type cast error anytime.
Here is an example that shows you how to test this.
Note:A child is a type of parent and the vice versa is not true.


<?xml version="1.0" encoding="utf-8"?>

<mx:Application

creationComplete="test()"

xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute">

<mx:Script>

<![CDATA[

import mx.controls.Alert;

import mx.events.CollectionEvent;

import mx.collections.ArrayCollection;

private function test():void {

var parent:Parent = new Parent();

var child:Child = new Child();

if (child is Parent) {

Alert.show("Yes");

} else {

Alert.show("No");

}

}

]]>

</mx:Script>

</mx:Application>

}




Bookmark and Share

Flex - Check if a property exists in an Object

When dealing with typeCasting its essential to test if the objects are compatible before having a
typecast statement.Forgetting to do this results in fragile code that might throw a type cast error anytime.
Here is an example that shows you how to test this.

Note:A child is a type of parent and the vice versa is not true.

<?xml version="1.0" encoding="utf-8"?>
<mx:Application
creationComplete="test()"
xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute">
<mx:Script>
<![CDATA[
import mx.controls.Alert;
import mx.events.CollectionEvent;
import mx.collections.ArrayCollection;

private function test():void {
var parent:Parent = new Parent();
var child:Child = new Child();

if (child is Parent) {

Alert.show("Yes");

} else {

Alert.show("No");

}

}

]]>

</mx:Script>

</mx:Application>

}



Bookmark and Share

Monday, November 17, 2008

Understanding [Bindable]

One of the most tricky and less understood features of flex is Binding.

Sure binding on first sight, is a very simple concept to grasp , but when one tries to apply it practically , one can have himself pulling his hair out.

Read this before you become a virendar sehwag look alike J.

 

My first doubts on the way [Bindable] arouse when I tried to use the bindable variable on an expression .

I was just wondering if having an expression based on a bindable variable would recompute itself , whenever the variable changed?

I had something like this

 

[Bindable]

private var test:Number = new Number();

 

private function changeText():void {

            this.test=new Number(nameInput.text);

                 }

 

And I set the value of the bindable variable on button click

 

<mx:HBox width="100%">

                        <mx:Form>

                                   <mx:FormItem label="valueOfTest">

                                                <mx:TextInput id="nameInput" width="100"/>

                                    </mx:FormItem>

 

                                    <mx:FormItem label="Check the Binding effect here">     

                                                <mx:TextInput id="valueAfterChange" text="{test > 1}" width="100"/>

                                    </mx:FormItem>

 

                                    <mx:FormItem>

                                                            <mx:Button label="Set" click="changeText()"/>

                                    </mx:FormItem>

 

The value of the second text input did change and the expression was recomputed.

Cool enough. When I removed the [Bindable] metatag the value did not change.That was expected~.

The fact is that the events are not triggered on components that use the variable.Simple.

 

Now, what if you have an function that is assigned to the text attribute of the second text input?

 

See this,

I changed the second text inputs definition to

 

<mx:TextInput id="valueAfterChange" text="{getTextForMe() }" width="100"/>

 

And I added the function which goes like this

                                    private function getTextForMe():Number {

 

                                                return test + 10;

 

                                    }

 

My first instinct was that the value would automatically be recomputed , but it did not.

It turns out that the function should be declared as [Bindable] too, so that the property would be recomputed too.

                                   

                                    [Bindable]

                                    private function getTextForMe():Number {

                                                return test + 10;

                                    }

 

 

 

Alright so here is the moral of the story.

 

Have your variables annotated with [Bindable] meta tag whenever the changes to it has to reflect elsewhere.

Changes to variables that are bindable will reflect even if the variable was used in an arithematic expression. I mean any property that uses the bindable variable to compute, its value will be recomputed.

If you are using functions to determine value for  any property that uses the bindable variable , have the function declared as bindable.

 

 

Hope it helps I did actually stop you from becoming a virendar sehwag llok alike J




Bookmark and Share

Friday, November 14, 2008

Watch for Changes in an ArrayCollection

ArrayCollection is one of the most beautiful aspects of flex which makes it what it is. When dealing with ArrayCollections, one may want to have some kind of a callback when the items are changed.

This is how you can do it.

The magic lies in  flash.events.Event.CollectionEvent. To detect a change just add a listener to the CollectionEvent.COLLECTION_CHANGE on the arrayCollection.

Even if your array collection is not bindable, this is a sure shot way to get notified of changes made to the array collection.

NOTE:The event will be triggered only when you add or delete items from the array collection and not when it is re assigned or re initialized  and not when you change the values of item within.

 

Here is the example:

 

<?xml version="1.0" encoding="utf-8"?>
<mx:Application
    creationComplete="setUpListeners()"
     xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute">
    <mx:Script>
        <![CDATA[
            import mx.controls.Alert;
            import mx.events.CollectionEvent;
            import mx.collections.ArrayCollection;
            private var testAC:ArrayCollection = new ArrayCollection();
           
            private function setUpListeners():void {
                testAC.addEventListener(CollectionEvent.COLLECTION_CHANGE,showChange);
            }
            private function changeArrayCollection():void{               
                var obj:Object = new Object();
                obj.name=nameInput.text;
                obj.age=ageInput.text;
                testAC.addItem(obj);
                //var temp:ArrayCollection = new ArrayCollection();
                //temp.addItem(new Object());               
                //testAC=temp; Will not trigger!
                //Note:testAC=new ArrayCollection(); Will not trigger!
               
            }
            private function showChange(eve:CollectionEvent):void {
                Alert.show("Collection Changed.Operation was of type->"+ eve.kind
                + "at location-> " + eve.location);
               
            }
        ]]>
    </mx:Script>   
    <mx:HBox width="100%">
        <mx:Form>
            <mx:FormItem label="name">
                <mx:TextInput id="nameInput" width="100">
                   
                </mx:TextInput>               
            </mx:FormItem>
            <mx:FormItem label="age">
                <mx:TextInput id="ageInput" width="100">
                   
                </mx:TextInput>               
            </mx:FormItem>
            <mx:FormItem>
                <mx:Button label="change" click="changeArrayCollection()">
                   
                </mx:Button>
            </mx:FormItem>
        </mx:Form>
       
    </mx:HBox>
</mx:Application>
 

Hope it helps!!       

        

 

 

 

 





Bookmark and Share

Thursday, November 13, 2008

Hide Show a Tab on Tab Navigator

Right, just a short code-snippet I'd like to share for those who have been searching for a solution for ages (like I have). I was looking for a way to hide specific tabs in a TabNavigator in Flex 3 without removing a child form the ViewStack

This is not possible by simply hiding a child in the viewstack (child.hide = true) or by setting its visibility to false (child.visible = false). 

With an easy workaround you can set the visiblity of a specific tab to false: 

tabNavigator.getTabAt(1).visible = false;

Probably more people have found this solution, but I couldn't find it on the web so here it is.

 





Bookmark and Share

How to copy an ArrayCollection

 

There are many ways to copy an arrayCOllection to another one.Here is a couple of them

Initialize the new array with the older arrayCollection's source.

Example :var a : ArrayCollection = new ArrayCollection(array);   var b : ArrayCollection = new ArrayCollection(a.source);

Use mx.utls.ObjectUtil.Copy

Example :var arrayCollection1 : ArrayCollection = ObjectUtil.copy(arrayCollection2)

Hope it helps!





Bookmark and Share

Proper Form Validation in flex

Validators in flex have always been a mystery and I happened to encounter one of those really upsetting quirks in one of my projects.What I am talking about is the un invited red borders that get visible when you tab out of fields which have validators assigned.One would expect that the error tooltip would also appear when the red borders come.But you know, flex throws some unpleasant surprises at you at times and this is one such thing.Don't contemplate harrikiri yet :-). Every problem has a solution hidden inside it.

 

This is how it looks

 

 

 

            Turns out that the ToolTipManager can help one hiding and showing tooltips as and when requried.

           

            Here is some sample code.

 

            <mx:FormItem label="Your name">

                <mx:HBox>

                    <mx:TextInput id="yourName" change="onChangeText(event);" focusOut="onChangeText(event);"/>                

                </mx:HBox>

            </mx:FormItem>

 

            private function onChangeText(eve:Event):void {

                       

          var target:TextInput = eve.currentTarget as TextInput;

if (target.text == "")

                        {

            // Has the error message ToolTip already been created?

            // (A reference to created ToolTip instances is saved in a hash called errorMessageToolTips.)

                   // Create the ToolTip instance.

        var pt:Point = new Point(target.x, target.y);

        pt = target.contentToGlobal(pt);

        var errorTip:ToolTip = ToolTipManager.createToolTip(errorMessages[target.name] + " cannot be empty", pt.x + target.width + 5, pt.y) as ToolTip;

        errorTip.setStyle("styleName", "errorTip");

        errorTip.visible=true;      

                        }

            }

 

           

 

            Comments Welcome .. As always.       

 





Bookmark and Share