JSON and HashMap

DWR is used for easy 'AJAX for JAVA' and is employed to call Java methods from Javascript (version 2.0 + supports reverse-AJAX too).

Working on the ShopprStream(earlier known as WEB122) has helped me get acquainted with many facets of web-development.


Now I have a Java method that returns a generic HashMap object ;
For this example lets consider that the key is of type String
And the elements are instances of the class CustomClass with name (of type String) as instance variable

The DWR call will return a JSON object. This is how we can access the data

for (var key in hashMap)
{
     //if not using Firebug, comment out console.log statements
                        
     //'key' is the key in the HashMap
     console.log("key : "+ key);
          
    //this will give the no. of elements stored corresponding to the 'key'
    console.log("hashMap[key].length: "+ hashMap[key].length);
                 
    //Access individual elements corresponding to the 'key'
    for(var i=0; i<hashMap[key].length; i++)
    {
    console.log("hashMap[key][i].name: " + hashMap[key][i].name);
    }
}

If the HashMap contains custom objects, make sure it has a corresponding converter entry in the dwr.xml file

for example, if my class is called CustomClass, then write as

<convert converter="bean" match="com.pramati.web122.imsupport.ContactDetail"/>

Here, abc.xyz is the package structure

If object returned is hashmap, then values can be accessed as:
hasMap[key]

If object returned is hashmap, then values can be accessed as:
hasMap[key][0], hasMap[key][1], hasMap[key][2] . . . . .

Helpful JavaScripts

To bring focus to a text box / button or any other element

just add this javascript in the HTML code:

<script type="text/javascript">
   document.getElementById("elementId").focus();
</script>

where elementId the id of the element on which the focus is to be set

for example, the following code will bring focus to the textbox that has the id email

<input type="text" id="email" />
<script type="text/javascript">
   document.getElementById("email").focus();
</script>