Java Hair

One of the cool features of the ADF Business Components layer in 11g is the ability to add custom properties to Entity or View objects. It’s a neat feataure but up until this point I hadn’t really any need to use them.

Then, when I was trying to implement a View object as only allowing updates, not inserts or deletes, I learned that there isn’t really a way to declaritively do this in ADF 11g. It seemed like one of those things that should be available, but the help says this:
“Some 4GL tools like Oracle Forms provide declarative properties that control whether a given data collection allows inserts, updates, or deletes. While the view object does not yet support this as a built-in feature in the current release, it’s easy to add this facility using a framework extension class that exploits custom metadata properties as the developer-supplied flags to control insert, update, or delete on a view object.”

The above quote is from section 37.11 of the Fusion Developer’s Guide for Oracle ADF. The section is actually titled “Declaratively Preventing Insert, Update, and Delete” which sounded like exactly what I wanted, but when i read the section I found that little bit of discouraging news. The last few words were encouraging, I thought using custom proerties to control insert, update, or deletes would be perfect, then I read on.

The next couple paragraphs seem to indicate that it would be a good idea to create instances of the view object that are called ViewObjectInsert, ViewObjectUpdate, and ViewObjectDelete, generic framework code could be used to look for these View instances and based on if a custom property is set then blah, blah, blah. I think it actually said something about looking up the phase of the moon also.

I’m not sure why you would want to have custom instances to determine whether or not customer properties should be looked up or not, why not just use custom properties? Anyway, that is the route I decided to take and it turned out to be pretty simple.

Chirs Muir had written an article on using custom properties to automatically convert the case of input and I used his article along with the help section of the Fusion Developer’s guide to come up with this solution. Thanks Chris!

1. Create a custom ViewObject implementation class.
This is done by creating a class that extends the Oracle View Object.

1a. Right click on the package you would like your custom class to reside in.
1b. Click on Simple File in the left pane and Java Class on the right pane.
1c. Name the file and make sure it extends the ViewObjectImpl class.

2. Create a method to check the custom property.

     private boolean isAllowed(String action) {
         boolean result = true;
         if (getViewDef() != null) {
             if (getViewDef().getProperty(action) != null) {
                String actionProperty = (String) getViewDef().getProperty(action);
                if (actionProperty != null) {
                    if ("false".equals(actionProperty)) {
                        result = false;
                    }
                }
             }
         }
         return result;
     }

3. Override the appropriate methods.
3a. Override the createRow method to check if Create is allowed, and if it isn’t throw an exception.

    public Row createRow() {
        if (isAllowed("insert")) {
            return super.createRow();
         } else {
            throw new JboException("Create not allowed in this view");
         }
    }

3b. Override the removeCurrentRow method in the same way.

    public void removeCurrentRow() {
        if (isAllowed("delete")) {
             super.remove();
         } else {
            throw new JboException("Delete not allowed in this view");
         }
    }

4. Add the necessary declarations to the View Object you wish to have these features.
4a. Add the following line to the attributes of the View Object to have it implement the framework class.

	ComponentClass="com.vgo.demo.framework.MyCustomViewObjectImpl"

4b. Add the necessary custom properties to the View Ojbect. Click on the General section of the Overview tab of the view object. Open the section for Custom Properties and click the green plus. Change the name to “insert” and the value to “false”. Click on the green plus to add another cusom property, name this one “delete” and set the value to “false”.

5. That’s it, it is that simple. Now run an Application Module that contains that View and try to insert or delete, when you do, you should see the exception that is thrown to inform the user that the action is not permitted.

As you can see, custom properties in ADF 11g are sure to prove extremely useful in the future, I am sure this is but one potential use for them.