Pass list of strings to custom DMI

[kevboy]

I'm trying to pass a List of Strings to our custom DMI. I keep getting "cannot cast String to Collection" exceptions.

The DSRequest payload debug output shows something like:

...
values:{
    stringList:"[string A, string B, string 0, string 3, string 6]",
}
...

Below are the relevant code snippets...

Code to set attribute:

// otherList is an ArrayList<String>
valuesManager.setValue("stringList", record.getAttribute("otherList"));

Custom DMI:

public DSResponse add(DSRequest dsRequest) throws Exception {
    Map<String,Object> map = dsRequest.getValues();
    
    List<String> coiRecords = ((List<List<String>>) map.remove("stringList")).get(0);

...

ds.xml:

<field multiple="true" name="stringList" type="text" />

...not sure if multiple should be set for in the ds file.

I tried changing it to a string array then calling ValuesManager.setAttributeAsStringArray but I didn't have much luck there.

Thanks for your help in advance!

[Isomorphic]

Seeing this in the Dev Console:

...
values:{
    stringList:"[string A, string B, string 0, string 3, string 6]",
}
...

.. means you've passed a single String, and not a List or Array of Strings. So, yes, use ValuesManager.setAttributeAsStringArray() to provide the value - once you see it leave the browser as an actual String[], your server-side code looks fine.

[kevboy]

I changed the client-side code to use setAttributeAsArray. I also had to change the type of what I was passing from List<String> to String[] because it was causing JavaScriptObject conversion exceptions.

Now I get this in the output:

stringList:"[Ljava.lang.String;@3d342e"

and this exception:

java.lang.ClassCastException: java.lang.String cannot be cast to java.util.List

I then try to change my server code to:

String[] stringList = ((List<String[]>) map.remove("stringList")).get(0);

then I get this exception:

java.lang.ClassCastException: java.lang.String cannot be cast to [Ljava.lang.String;

[kevboy]

I also tried changing the server code to

String[] stringList= (String[]) map.remove("stringList");

But then I got:

java.lang.ClassCastException: java.util.ArrayList cannot be cast to [Ljava.lang.String;

[Isomorphic]

Never mind the various server consequences until you see an actual String Array being transmitted, which will look like this:

...
values:{
    stringList:["string A","string B","string 0","string 3","string 6"],
}
...

The question is how your string array is getting mangled before getting to the server. Can you show complete code for applying a String[] as a value on a ValuesManager such that it ends up somehow not as a String[] in the RPC tab? Also please indicate exact version, browser, etc.

[kevboy]

Thanks for the tip. I just noticed we call the setValue method (I know it's not recommended but it's for MVP purposes) that takes a String and an Object then it calls the specific setValue method with the specific type.

Here's the code for that:

/**
 * Takes a general Object and calls a specialized setValue method
 * 
 * @param key   key of value to set
 * @param value value to set
 */
@SuppressWarnings("rawtypes")
@Override
public void setValue(String key, Object value) {
    if (key == null) {
        throw new IllegalArgumentException("Attempting to set null key with value: " + value);
    }
    
    if (value == null) {
        throw new IllegalArgumentException("Attempting to set null value for key: " + key);
    }
    
    if (value instanceof Boolean) {
        super.setValue(key, (Boolean) value); 
    } else if (value instanceof DataClass) {
        super.setValue(key, (DataClass) value); 
    } else if (value instanceof DataClass[]) {
        super.setValue(key, (DataClass[]) value); 
    } else if (value instanceof Date) {
        this.setValue(key, (Date) value); 
    } else if (value instanceof Double) {
        super.setValue(key, (Double) value); 
    } else if (value instanceof JavaScriptObject) {
        super.setValue(key, (JavaScriptObject) value);
    } else if (value instanceof Map) {
        super.setValue(key, (Map) value); 
    } else if (value instanceof Record) {
        super.setValue(key, (Record) value); 
    } else if (value instanceof Record[]) {
        super.setValue(key, (Record[]) value);
    } else if (value instanceof String){
        // Do not call toString() on a String. GWT contains a bug when casting a String to a String
        super.setValue(key, (String) value);
    } else {
        super.setValue(key, value.toString());
    }
}

This would explain the result from the debug output as a toString() of a String[] would output something like that.

I looked at the javadoc for ValuesManager and didn't see a setValues(String,String[]) so I was wondering how we should call setValues with the String array.

We're using a nightly build from 9/28/10 of 2.3 (waiting for schedule to allow to upgrade to 2.4) in IE7.

[Isomorphic]

Not sure which setValue() this is, but this should be corrected in 2.4. If you need a workaround for 2.3 (seems like upgrading now is the best workaround) you can create a JavaScriptObject representing a JavaScript Array of String and use that with the setValue() method.

[kevboy]

I'm sorry--I meant to say that was a setValue method we wrote on our end to facilitate MVP pattern.

I added a new case to the method and was able to convert the String[] argument to a JavaScriptObject:

...
} else if (value instanceof Object[]) {
    // Convert to JavaScriptObject
    super.setValue(key, JSOHelper.arrayConvert((Object[]) value));
}
...

It then showed up on the server side as a List<String>. Thanks for all your help!