Dynamic creation of class at runtime

I need to be able to dynamically create an instance of a
class that isn't known until runtime - actually based on the
filename
so in my fla:
var className:String="Test"; /* code to get a class name
derived from the filename */
var obj = new [className]();
trace(obj);
the code above only works if i put the literal directly in [
like so:
var obj = new ["Test"]();
is there a way to do this???
Any help much appreciated
cheers Steve

This might help you out:
http://dynamicflash.com/2005/03/class-finder/
"steveanson" <[email protected]> wrote in
message
news:e3fcnv$6c7$[email protected]..
> I need to be able to dynamically create an instance of a
class that isn't
known
> until runtime - actually based on the filename
>
> so in my fla:
> var className:String="Test"; /* code to get a class name
derived from
the
> filename */
> var obj = new ();
> trace(obj);
>
> the code above only works if i put the literal directly
in
> like so:
> var obj = new ();
>
> is there a way to do this???
> Any help much appreciated
> cheers Steve
>
>
>

Similar Messages

Dynamic creation of classes

hi there
i was wondering if it was possible to create an instance of a
class (AS 2.0) at runtime, given just a string value for the class
name
eg, my first attempt was something like
var class_str:String = "MyClass1";
var inst
bject = new eval(class_str)();
now, "eval(class_str)" returns an object of type "function",
ie the function reference to the class constructor, and so all i
get is a new "function object"
any clues, or am i p***ing in the wind?
tia
bhu

I'm afraid "eval()" can't be used this way:
LiveDocs

Dynamic creation of class objects?

I have a requirement where in at runtime I would know the class name, method name, properties, interface..and coding lines to be put into a method?
Can anyone suggest a way to create the consumable central class object with these details, activate it and without any manual intervention create this object in backend?

From other thread...use SEO* package

Dynamic creation of objects at runtime

supposed i want to create a tree structure and i use objects to represent the nodes...but i need the user to specify the number of nodes in the tree...so the user will enter 10 or 13 whatever.So how do we create those nodes dynamically...i know how to add nodes ...umm Example
Node A=new node('A');
Node B=new node('B');
//this creates a new node A of type node(user defined class)
but how to create it dynamicaaly
eg
for(i=1;i<=Totalnodes;i++)
Node A= new node('A');
} //well obviously this code is wrong .
Here is a copy of the main program where nodes are added to the code and not specified by the user
public class Main {
     public static void main(String[] args)
          //Lets create nodes as given as an example in the article
          Node nA=new Node('A');
          Node nB=new Node('B');
          Node nC=new Node('C');
          Node nD=new Node('D');
          Node nE=new Node('E');
          Node nF=new Node('F');
          //Create the graph, add nodes, create edges between nodes
          Graph g=new Graph();
          g.addNode(nA);
          g.addNode(nB);
          g.addNode(nC);
          g.addNode(nD);
          g.addNode(nE);
          g.addNode(nF);
          g.setRootNode(nA);
          g.connectNode(nA,nB);
          g.connectNode(nA,nC);
          g.connectNode(nA,nD);
          g.connectNode(nB,nE);
          g.connectNode(nB,nF);
          g.connectNode(nC,nF);
.

Ugh i so messed up..ok ok im gonna explain clearly now coz i just kinda blurted out stuff before :P
ok So here is the main program :
public class Main {
     public static void main(String[] args)
          //Lets create nodes as given as an example in the article
          Node nA=new Node('A');
          Node nB=new Node('B');
          Node nC=new Node('C');
          Node nD=new Node('D');
          Node nE=new Node('E');
          Node nF=new Node('F');
          //Create the graph, add nodes, create edges between nodes
          Graph g=new Graph();
          g.addNode(nA);
          g.addNode(nB);
          g.addNode(nC);
          g.addNode(nD);
          g.addNode(nE);
          g.addNode(nF);
          g.setRootNode(nA);
          g.connectNode(nA,nB);
          g.connectNode(nA,nC);
          g.connectNode(nA,nD);
          g.connectNode(nB,nE);
          g.connectNode(nB,nF);
          g.connectNode(nC,nF);
          //Perform the traversal of the graph
          System.out.println("DFS Traversal of a tree is ------------->");
          g.dfs();
          System.out.println("\nBFS Traversal of a tree is ------------->");
          g.bfs();
And this is the Graph module:
import java.util.ArrayList;
import java.util.LinkedList;
import java.util.Queue;
import java.util.Stack;
public class Graph
     public Node rootNode;
     public ArrayList nodes=new ArrayList();
     public int[][] adjMatrix;//Edges will be represented as adjacency Matrix
     int size;
     public void setRootNode(Node n)
          this.rootNode=n;
     public Node getRootNode()
          return this.rootNode;
     public void addNode(Node n)
          nodes.add(n);
     //This method will be called to make connect two nodes
     public void connectNode(Node start,Node end)
          if(adjMatrix==null)
               size=nodes.size();
               adjMatrix=new int[size][size];
          int startIndex=nodes.indexOf(start);
          int endIndex=nodes.indexOf(end);
          adjMatrix[startIndex][endIndex]=1;
          adjMatrix[endIndex][startIndex]=1;
     private Node getUnvisitedChildNode(Node n)
          int index=nodes.indexOf(n);
          int j=0;
          while(j<size)
               if(adjMatrix[index][j]==1 && ((Node)nodes.get(j)).visited==false)
                    return (Node)nodes.get(j);
               j++;
          return null;
     //BFS traversal of a tree is performed by the bfs() function
     public void bfs()
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          Queue q=new LinkedList();
          q.add(this.rootNode);
          printNode(this.rootNode);
          rootNode.visited=true;
          while(!q.isEmpty())
               Node n=(Node)q.remove();
               Node child=null;
               while((child=getUnvisitedChildNode(n))!=null)
                    child.visited=true;
                    printNode(child);
                    q.add(child);
          //Clear visited property of nodes
          clearNodes();
     //DFS traversal of a tree is performed by the dfs() function
     public void dfs()
          //DFS uses Stack data structure
          Stack s=new Stack();
          s.push(this.rootNode);
          rootNode.visited=true;
          printNode(rootNode);
          while(!s.isEmpty())
               Node n=(Node)s.peek();
               Node child=getUnvisitedChildNode(n);
               if(child!=null)
                    child.visited=true;
                    printNode(child);
                    s.push(child);
               else
                    s.pop();
          //Clear visited property of nodes
          clearNodes();
     //Utility methods for clearing visited property of node
     private void clearNodes()
          int i=0;
          while(i<size)
               Node n=(Node)nodes.get(i);
               n.visited=false;
               i++;
     //Utility methods for printing the node's label
     private void printNode(Node n)
          System.out.print(n.label+" ");
And this is the node module:
public class Node
     public char label;
     public boolean visited=false;
     public Node(char l)
          this.label=l;
So my question is: How do i get the user to specify the number of nodes..i.e take input the number of nodes...add them to a tree....and how do i convert this graph into a tree

Help with dynamic creation of class object names

Hi all
Wonder if you can help. I have a class player.java. I want to be able to create objects from this class depending on a int counter variable.
So, for example,
int counter = 1;
Player p+counter = new Player ("Sam","Smith");the counter increments by 1 each time the method this sits within is called. The syntax for Player name creation is incorrect. What I am looking to create is Player p1, Player p2, Player p3.... depending on value of i.
Basically I think this is just a question of syntax, but I can't quite get there.
Please help if you can.
Thanks.
Sam

here is the method:
//add member
public void addMember() {
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    long phoneNumber;
    boolean isMember=true;
    this.memberCounter++;
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    firstName=askUser("Enter First Name: ");
    secondName=askUser("Enter Second Name: ");
    address1=askUser("Enter Street Name and Number: ");
    address2=askUser("Enter Town: ");
    phoneNumberAsString=askUser("Enter Phone Number: ");
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    while(members.hasNext()) {
      temp = (Player)members.next();
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      output=output + temp.getSecondName() + "\n";
      output=output + temp.getAddress1() + "\n";
      output=output + temp.getAddress2() + "\n";
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}//end addMemberOn running this, no matter how many details are input, the HashMap only gives me the first one back....
Any ideas?
Sam

Dynamic Creation of Class Name

I just want to create the class name on the fly.
Look the example below.
String className = "gui.Header";
className header = new className;
Let's assume that there is a Header class somewhere.
Is this possible? or is there a way to do this?

From what i understand, u wish to create an instance of a class whose name is known to you at runtime - correct me if i'm wrong - i'll answer based on my assumption. You can basically do that using Reflection in Java. I'm pasting sample code which shows how you do this:
The following sample program creates an instance of the Rectangle class using the no-argument constructor by calling the newInstance method:
import java.lang.reflect.*;
import java.awt.*;
class SampleNoArg {
public static void main(String[] args) {
Rectangle r = (Rectangle) createObject("java.awt.Rectangle");
System.out.println(r.toString());
static Object createObject(String className) {
Object object = null;
try {
Class classDefinition = Class.forName(className);
object = classDefinition.newInstance();
} catch (InstantiationException e) {
System.out.println(e);
} catch (IllegalAccessException e) {
System.out.println(e);
} catch (ClassNotFoundException e) {
System.out.println(e);
return object;
Hope the above helps.
John Morrison

Dynamic Creation of Items in Runtime through Application UI

We have a requirement where the Users wanted to have an option of creating an item dynamically. We developed and deployed a very simple application but the users want to have the flexibility of adding new columns (without vaildations and processing - just data) to some of the existing regions. They are not IT people and want a simple interface to add columns without IT involvement.
I thought of two options.
(a) To pre-create around 10 items in the table with column names as customize1...customize10 with varchar2(1000). Have a configuration table which stores the column names and Label. Create a Report based on a Pl/SQL function returning query, and using HTMLDB_ITEM to dynamically populate them. Iam not very keen about this approach as do not want to create unnecessary columns and have to do a lot of manual processing for the data manipulation.
a.1. Can we create a form (not a report) based on a pl/Sql function returning query.
(b) To have an interface which does an "Alter Table .... add column ...." to create the new column. In this case how can we include this column to an existing form. Can we use HTMLDB_ITEM to add (create) columns to an existing region?
(c) Any other suggestion ?
Would appreciate an answer on the way to go forward to this, and also to a.1.
Thanks

Hi Marc,
Thanks. I just tried something like this. Taking the EMP table example, (it doesn't matter which table), I created a region based on a Pl/Sql function returning SQL query
( I selected the vertical report template including nulls to display it like a form ) :
DECLARE
v_sql VARCHAR2(3000) ;
mn_idx NUMBER := 1 ;
BEGIN
v_sql := 'SELECT ' ;
FOR recs IN (SELECT * FROM ALL_TAB_COLUMNS WHERE TABLE_NAME = 'EMP' ORDER BY COLUMN_ID)
LOOP
v_sql := v_sql || 'HTMLDB_ITEM.TEXT(' || mn_idx || ',' ||
recs.column_name || ') ' || recs.column_name || ', ' ;
mn_idx := mn_idx + 1 ;
END LOOP ;
v_sql := SUBSTR(v_sql, 1, LENGTH(v_sql) -2) ;
v_sql := v_sql || ' FROM EMP WHERE EMPNO = 7369 ORDER BY 1 ' ;
RETURN v_sql ;
END ;
This allowed me to do my updates etc.., Then I created a button called 'Apply' and a process called 'update_changes' on button click and defined this:
DECLARE
v_sql varchar2(1000) ;
mn_ctr NUMBER := 1 ;
BEGIN
v_sql := 'BEGIN UPDATE EMP SET ' ;
FOR recs IN (select COLUMN_ID, COLUMN_NAME, DATA_TYPE
from all_tab_columns where table_name = 'EMP'
ORDER BY COLUMN_ID) loop
-- Make changes here if required- this is assuming 9 columns --
v_sql := v_sql || recs.column_name || ' = HTMLDB_APPLICATION.G_F0' || mn_ctr || '(1),' ;
mn_ctr := mn_ctr + 1;
end loop ;
v_sql := substr(v_sql, 1, length(v_sql) - 1) ;
v_sql := v_sql || ' WHERE EMPNO = 7369; END ;' ;
execute immediate (v_sql) ;
END ;
Since this is for example, I didn't include code for Checksum and hardcoded empno = condition and have provision for 9 columns. I made some changes and tried saving it and I was able to do it.
I altered the table to add a column / drop a column and when I relogin, Iam able to see the changes.
Can you tell me if there could be any drawbacks in this approach ?.

Dynamic creation of class and calling methods

I've got and interface called Transformation and then two implementations called TxA and TxB, where TxA and TxB have their own attribtues and setter and getters for these attributes.
The question is, I need to create instances of TxA and TxB and called the setter and getters where I at runtime I only know the attribute to set, how can I create and instance and call the right getters and setters methods?
Thanks in advance

Smart money says your design sucks and needs to be rethought entirely. Can we get specifics?
Drake

Dynamic loading of a class at runtime with known inheritance

Hi,
I am trying to dynamically load a class during runtime where I know that the class implements a particular interface 'AInterface'. Also, this class may be linked to other classes in the same package as that class, with their implementations/extensions given in their particular definitions.
The class is found by using a JFileChooser to select the class that implements 'AInterface', and loaded up.
Because the name of the class can be practically anything, my current approach only works for certain classes under the package 'Foo' with classname 'Bar'. Some names have been changed to keep it abstract.
private AInterface loadAInterface(URL url) throws Exception {
     URL[] urls = { url };
     // Create a new class loader with the directory
     URLClassLoader cl = new URLClassLoader(urls);
     // Load in the class
     Class<?> cls = cl.loadClass("Foo.Bar");
     return (AInterface) cls.newInstance();
}As you can see, all that is being returned is the interface of the class so that the interface methods can be accessed. My problem is that I don't know what the class or package is called, I just know that the class implements AInterface. Also note that with this approach, the class itself isn't selected in the JFileChooser, rather the folder containing Foo/Bar.class is.

ejp wrote:
The class is found by using a JFileChooser to select the class that implements 'AInterface', and loaded up.
Also note that with this approach, the class itself isn't selected in the JFileChooser, rather the folder containing Foo/Bar.class is.These two statements are mutually contradictory...My apologies, I worded that wrong. My current approach (the one given in the code) selects the root package folder. However, what I want to be able to do, is to simply select a single class file. The current code just makes some assumptions so that I can at least see results in the program.
As you said, if the root of the package hierarchy is known, then this could be achieved. The problem is that the user either selects the package root or the AInterface class, but not both.
Is there a way to get package details from a .class file to be used in the actual loading of the class?

Dynamic or Static Class

Dynamic or Static Objects
It seems to me there is a big cliff at the point of deciding to instantiate your class at runtime or static load
on start-up.
My swf apps have a pent-up burst that happens a couple seconds into the run. I think I get this on most
web pages that have flash banners.
Flash apps that have a loader bar can take 60 secs. These ones usually come on with a bang with a lot of
high quality graphics.
Therer is a big processor spike at start-up with the browser loading http page. Flash seems to want a big spike
with its initial load. The javascript embed doesn't help either.
How to get a smooth start-up? Me English good.

This seems like a matter of correctness, only indirectly relating to speed.
The speed that a SWF loads from a web page is determined by many things, like server connection speed, client connection speed, browser cache size, client RAM, etc. Having static vs. dynamic classes would not impact this very much.
First of all, "static objects" is kind of an oxymoron because you can't instantiate (create an object) of a static class. I would say that having static variables/methods in a class is usually when you want some shared values/functionality without requiring an actual object (taking up memory) -- although static practices certainly extend beyond just this. I always try to think of a Math class. You wouldn't have to have to say m = new Math() just to use some common methods (square, sin, cos, etc.) or values (pi, e, etc.). They become kind of like "global constants/methods" in a sense (not to invoke the debate over correctness of that wording).
In short, it's more of a memory issue, which will like not have much influence over loading speed. If you want to improve your loading speed, you can try to delay the creation of your objects based on certain events instead of having them all load at startup.
How to get a smooth start-up? Me English good.

Dynamic creation of TabStrip

Hi,
I want to create a tabstrip dynamically.The tabstrip should have 3 tabs, and in each of the tabs i want to put some UI elements like a label, input field, dropdown, tables.........etc.
Im able to create the tabstrip and add tabs to it dynamically.
I've even created the UI elements which i wanted to put in the tabs.............But im not able to proceed as i dont know how to add the UI elements to the tabs.......
Can anyone tell me how to add UI elements to a tab in a tabstrip?
Regards,
Padmalatha.K
Points will be rewarded.

Hi,
Following code will help you to understand the dynamic creation and adding them
//Tabstrip
       IWDTabStrip tabStrip = view.createElement(IWDTabStrip.class);
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       IWDTab tab = view.createElement(IWDTab.class);
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//Finally add this tabstip to either your root container or some other container.
Regards
Ayyapparaj

Dynamic creation of ComponentUsage

Hi people,
I want to reuse a view (ViewA) in different views (ViewB, ViewC, ViewD).ViewA has a quite complex logic, so it is necessary to outsource this view. Not only the logic, but also the count of UIElements and contextelements is quite large, for this I don't want to implement this part redundant in the views A, C and D.
I have to use ViewA in a table in the TablePopin UIElement. Every line of the table should have its own instance of ViewA. Is that possible?
My idea is it, to put the view in an own component. For every tableline I need an instance of the componentUsage. My problem is now, that I'm not able to create at runtime a ComponentUsage and at designtime I don't know how many instances I need. Is it possible in webdynpro to create dynamic instances of ComponentUsage?
If you know an other way, that prevents me from implementing the view and its logic more times, please tell me!
Thanks in advance,
Thomas Morandell

Hi Thomas,
just for clarification. Principally it is possible in Web Dynpro to dynamically create new component usages of the same type like an existing, statically declared one. This means after having defined a component usage of type ISomeComp (component interface definition) you can dynamically create new component usages which all point to the same component interface definition ISomeComp:
wdThis.wdGetISomeCompUsage().createComponentUsageOfSameType();
But this dynamic creation approach implies, that you must also embed the component interface view of this component usage to the view composition dynamically; and this is (unfortunately) quite cumbersome and complicated based on the existing Web Dynpro Java API (it is not yet optimized for a simple dynamic view composition modification.
Additionally, like Valery pointed out, the dynamic creation of new component usages is not compatible with table popins.
Regards, Bertram

Dynamic Java bean classes for XSD using JAVA (not any external batch or sh)

Hi,
How can we generate dynamic Java bean classes for XSD (dynamically support All XSD at runtime)?
Note: - Through java code via only needs to generate this process. (Not using any xjc.bat or xjc.sh from JAXB).
Thanks

Muthu wrote:
How can we generate dynamic Java bean classes for XSD (dynamically support All XSD at runtime)?
Pretty sure you can't. Probably can do a lot of them with years of work.
And can probably can do a resonable subset suitable for the business at hand with only a moderate effort.
Note: - Through java code via only needs to generate this process. (Not using any xjc.bat or xjc.sh from JAXB).The Sun jdk, not jre, comes with the java compiler as part of it. You can create in memory class (I believe in memory) based on java code you create.
I believe BCEL alllows the same thing (in memory) but you start with byte codes.
You could just create a dynamic meta data solution as well, via maps and generic methods. Not as fast though.

Dynamic creation of business graphics.

Hi,
i have a piece of code which dynamically create a business graphics. If i use the same node data and create BG in statically.. i am able to view the graph. In case of dynamic creation , i am getting graphical rendering error. Have i missed something here..
The piece of code i had used is..
     IWDBusinessGraphics bg = (IWDBusinessGraphics)view.createElement(IWDBusinessGraphics.class,null);
          IWDCategory c = (IWDCategory)view.createElement(IWDCategory.class,null);
     //     c.setDescription("tableutility");
          c.bindDescription(wdContext.getNodeInfo().getAttribute(IPrivateSDNUtilityView.IContextElement.TEST));
bg.setCategory(c);
          bg.setDimension(WDBusinessGraphicsDimension.PSEUDO_THREE);
          IWDSimpleSeries ss = (IWDSimpleSeries)view.createElement(IWDSimpleSeries.class,null);
          ss.bindValue(wdContext.nodeDepartments().getNodeInfo().getAttribute(IPrivateSDNUtilityView.IDepartmentsElement.NO_OF_PEOPLE));
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          bg.setChartType(WDBusinessGraphicsType.COLUMNS);
          bg.bindSeriesSource(wdContext.nodeDepartments().getNodeInfo());
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Please help.
Regards
Bharathwaj

Please got through following link
<a href="/people/sap.user72/blog/2006/05/04/enhancing-tables-in-webdynpro-java-150-custom-built-table-utilities:///people/sap.user72/blog/2006/05/04/enhancing-tables-in-webdynpro-java-150-custom-built-table-utilities

Dynamic Creation of Buttons and Actions HELP

Hi there,
I have got a problem (or maybe even two) with the dynamic Creation of buttons. The code below creates the buttons.
My main problem is, that the parameter created for the button's action isn't propagated to the assigned event handler. I get a null, though the name of the parameter in the event handler and the name of the parameter added to the action are the same.
Could it also be that I'm always using the same action? I.e. does wdThis.wdGetAddElementAction() always return the same action instance? If yes, how can I create individual actions for each button?
Any help is appreciated!
Cheers,
Heiko
"    for(int i=rootContainer.getChildren().length; i<wdContext.nodeFeature().size();i++)
               IPrivateVCT_Feature.IFeatureElement featureElement = wdContext.nodeFeature().getFeatureElementAt(i);
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               IWDCaption header = (IWDCaption) view.createElement(IWDCaption.class, featureElement.getName()+"_Header");
               header.setText(featureElement.getName());
               featureTray.setHeader(header);
               featureTray.setExpanded(false);
               rootContainer.addChild(featureTray);
               IWDButton button = (IWDButton) view.createElement(IWDButton.class, featureElement.getName()+"_Button_AddElement");
               IWDAction actionAddElement = wdThis.wdGetAddElementAction();
               actionAddElement.getActionParameters().addParameter("featureIndex", new Integer(i).toString());
               button.setOnAction(actionAddElement);
               button.setText("Add Element");
               featureTray.addChild(button);

Hi Heiko,
You have done everything correctly....except for 1 line
in the code...
Replace the following line in your code:
actionAddElement.getActionParameters().addParameter("featureIndex", new Integer(i).toString());
Replace the above line with this code:
button.mappingOfOnAction().addParameter("featureIndex",i);
Actually in your code, you are not associating the parameter with the button...
Note that addParameter(...) comes with two signatures: addParameter(String param, String value) and addParameter(String param, int value). You can use any of them based on yuor need.
Hope it helps,
Thanks and Regards,
Vishnu Prasad Hegde

Dynamic creation of class at runtime

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