using Vector and Hashtable as a bean for dwr

Question

I want to write a DWR function that prepares a Vector of Hashtable's and returns to the javascript and there in javascript i need to iterate a Vector and print the content of Hashtable.

My DWR function is:

public Vector getEmployeeData() {
   Vector employeeData = new Vector();
   // some other content to prepare vector

   return employeeData;
}

And i have configured dwr-servlet in web.xml properly and content in dwr.xml is:

<create creator="new" javascript="Employee" scope="script">
  <param name="class" value="com.test.DWREmployeeManager"/>
</create>
<convert match="java.util.Hashtable" converter="bean"/>
<convert match="java.util.Vector" converter="bean"/>  

But my problem is when i called this dwr method from javascrit i am getting empty array as a result to the dwr call-back function.

Can anybody suggest the solution for this problem..

Answer 1

Instead of using the two tags,

<convert match="java.util.Hashtable" converter="bean"/>
<convert match="java.util.Vector" converter="bean"/>  

I used the below convert tag:

<convert converter="collection" match="java.util.Collection"/>

Now its working fine.

Thanx

Answer 2

I suspect your problem here is that you're telling DWR to convert the Collection objects as beans. You shouldn't need to do this, nor do you want to -- they're not beans, they're collections.

See: http://directwebremoting.org/dwr/server/dwrxml/converters/collection.html

Moreover, as in my comment above, you probably want to use a List (Array or Linked), and a HashMap. If you're using Java 5 or newer, you probably should add type declarations.

Here's what I suggest: (You didn't specifically show your hashtable code, so I'm just assuming a map keyed off some string.)

public List<Map<String,EmployeeData>> getEmployeeData() {
    List<Map<String,EmployeeData>> employeeData = new ArrayList<Map<String,EmployeeData>>();
    // some other content to prepare list

    return employeeData;
}

In dwr.xml, you need to remove the two converter lines, and add one:

<convert match="com.test.EmployeeData" converter="bean"/>

(and make sure there are proper getter and setter methods for that bean).