JT’s Blog

Using bindData Method in a Grails Service

Grails controllers get a method called bindData which allows you to take the parameters map and bind the values to the properties of a domain object.  The method works nicely because it handles a lot of the type conversions for you.  This method works similar in fashion to the properties method, but it offers you more control.  Using bindData, you can include or exclude properties.   Here is the complete documentation for the bindData method.

I have a service which parses xml to domain objects.  I originally was walking the xml, casting the name value pairs to a map, and then using the properties method.  This was working well for me, until I needed the control offered by the bindData method.  When I tired to switch, I ran into a small gotcha.  Grails was throwing a method not found error.  Turns out bindData is a dynamic method that the Grails framework adds to controllers for you, but not services.

After a little digging through the Grails source code, I found the class used for the bindData dynamic method.  To add it to your services you will need to import the following:

import org.codehaus.groovy.grails.web.metaclass.BindDynamicMethod

I’m not going to get too fancy for a one off usage.  I just need to create an instance and call the invoke method. The method signature of invoke is Object, string, Object[]. I originally wrote my call as follows:

        BindDynamicMethod bind = new BindDynamicMethod()
 
        def args =  [ po, params, [exclude:['supplierAddress', 'shipToAddress', 'billToAddress', 'purchaseOrderDetail' ]] ]
 
        bind.invoke( po, 'bind', args)

But this was not happy in crossing the Goovy/Java barrier.  Groovy was treating my ‘args’ object as an ArrayList, not an array of Objects.  ANd Java was not happy about this.  Easy enough to fix with a cast.

        bind.invoke( po, 'bind', (Object[])args)

Looking at the source code of BindDynamicMethod, it seems that the first two parameters are just along for the ride.  All the program logic is applied to the third parameter, the Object array.  The object array is pretty much the call you would have done in a controller to the actual bindData() dynamic method.

So far this seems to be working ok for me.  Hopefully, this post gets someone over a little speed bump in the future.

This entry was posted on Tuesday, January 5th, 2010 at 6:43 pm and is filed under Uncategorized. The entry is tagged under Grails, Groovy. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.