Access to model object by EL in javascript function?

Question

Here is my markup, I am using jtsl core tag

<c:forEach var="attr" items="${attributes}">
    <c:when test='${attr.controlType == "textField"}'>
        <script>createTextField("${attr}");</script>
        </c:when>
</c:forEach>

So the "attributes" is a list of objects which resides in the model.

I want to call the createTextField function and I want access to the "attr" in that function.

Here is my function, but I can't get access to the object, says it is undefined.

function createTextField(object) {
    document.write(object.name);        
}

Any ideas? would be appreciated.

BalusC · Accepted Answer · 2012-01-31 19:28:58Z

4

This is not going to work. Java and JavaScript doesn't run in the same environment. You're basically passing attr.toString() to the JavaScript function which look by default like com.example.ClassName@hashcode. The JavaScript String object doesn't have a name property.

There are basically two ways to get it to work:

You need to convert the Java object as represented by #{attr} to a string which conforms the JavaScript object notation (also known as JSON). E.g.
```
<script>createTextField(${attr.asJson});</script>
```
with something like (with little help of Gson):
```
public String getAsJson() {
    return new Gson().toJson(this);
}
```
You can of course also manually build it using StringBuilder or something. JSON format isn't that hard.

Pass only the property/properties of interest as long as they can be represented as String. E.g.

<script>createTextField("${attr.name}");</script>

with

function createTextField(name) {
    document.write(name);        
}

answered Jan 31, 2012 at 19:28

BalusC

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4 Comments

Shehryar Farooq Over a year ago

Thanks, in this case option 2 will not work because I have a lot of fields in the object that I need in the function so, I have to use option one, but I am confused, I know what JSON is but dont understand what you meant by number 1. Can you please explain in a bit more detail?

BalusC Over a year ago

What part exactly don't you understand? Option 1 just tells you that you should convert the Java object to JSON so that you can easily print it as a valid JS function argument.

Shehryar Farooq Over a year ago

how to convert that object to a JSON, and then how to extract the values from that JSON within that JS function

BalusC Over a year ago

Uh, just use Gson or any arbirary Java based JSON parser API to convert a Java object to JSON string, or create a String in JSON format yourself with StringBuilder. The format should ultimately end up something like {"name":"somevalue", "otherproperty":"othervalue"} etc. Your JS createTextField() function can be kept untouched as it already retrieves a valid JS object when using JSON. You said that you know what JSON is, but after all you apparently don't understand JSON at all. What exactly is your problem?

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