Common ADF Mistakes - Conversion pages to page fragments

Suppose you have developed ADF task flow with pages (not page fragments) and later on you decide that these pages should be page fragments, and you convert that taskflow to support page fragments. After conversion, if you get this error

java.lang.IllegalStateException: Attempt to validate an already invalid RegionSite:

Check whether you have used PageController for page or not. If you used then convert it to RegionController. ADF does not give you indication of this. If you want to debug error, do the following:

• Goto bindings of page on which you dropped taskflow containing page fragments.
• In Executables, click the taskflow and set its property "activation" to "immediate"
• Now run and you will get detailed error.

Update

It can also occur if your taskflow is calling any method before page loading and that method is throwing some error.

Setting datasource name programmatically for ADF Application

While working on an enterprise application for my client, i received a request from the client that data source name should not be hardcoded in the application and it should be configurable because client wants to deploy it more than one instance of application on the same server for different purposes like preview, production etc. So i googled it, and found excellent article 11g Dynamic JDBC Credentials for Model 1, Struts, Trinidad, and ADF Faces Rich Client
Here it is simplified version:
You will have to extend two following classes:

• EnvInfoProvider
• DefaultSessionCookieFactory

EnvInfoProvider
This is main interface and datasource name will be set in the implementation of this interace. You will have to implement following three methods:

• public Object getInfo(String propName, Object object)
• public void modifyInitialContext(Object initialContext)
• public int getNumOfRetries()

Only important method for our scenario is getInfo method. It is used to set new datasource name. Sample implementation is given below:

public Object getInfo(String propName, Object object) {
        String myDataSourceName = "test"; // You can set it through your logic
        if (object instanceof Hashtable) {
            Hashtable connectionEnv = (Hashtable)object;
          System.out.println(connectionEnv.get(Configuration.JDBC_CONNECTION_NAME));
          String contextPath = (String)ADFContext.getCurrent().getSessionScope().get("contextPath");
              connectionEnv.put(Configuration.JDBC_DS_NAME,"java:comp/env/jdbc/"+myDataSourceName );
        }
        return null;
    }

    public void modifyInitialContext(Object initialContext) {
    }

    public int getNumOfRetries() {
        return 0;
    }

DefaultSessionCookieFactory

In order to configure custom implementation of EnvInfoProvider, you will have to extend DefaultSessionCookieFactory and override createSessionCookie method. Sample implementation is given below:

public SessionCookie createSessionCookie(String name,

String value,

ApplicationPool pool,

Properties properties) {




SessionCookie cookie = super.createSessionCookie(name, value, pool, properties);

Hashtable env = pool.getEnvironment();




env.remove(Configuration.JDBC_CONNECTION_NAME);

EnvInfoProvider provider = new MyEnvInfoProvider();

cookie.setEnvInfoProvider(provider);

return cookie;

}

Now last step is to configure this custom SessionCookieFactory. Open bc4j.xcfg of application module and add following element as a child of respected AppModuleConfig element

Accessing Runtime metadata for ViewObject and EntityObject

In Oracle ADF, ViewObject and EntityObject are two basic concepts and whole application revolves around these two type of objects. EntityObject corresponds to database table while ViewObject corresponds to Database View. ViewObject can be based on EntityObject, SQL or on transient attributes. Normally you create and design these two objects throug drag and drop in JDeveloper but sometimes you need some meta information about these two objects in business logic. In order to get metainfo, some understanding of underlying structure of these two objects should be.

Figure shown above illustrates the three primary interfaces ADF provides for accessing runtime metadata about view objects and entity objects. The ViewObject interface extends the StructureDef interface. The class representing the entity definition (EntityDefImpl) also implements this interface. As its name implies, the StructureDef defines the structure and the component and provides access to a collection of AttributeDef objects that offer runtime metadata about each attribute in the view object row or entity row. Using an AttributeDef, you can access its companion AttributeHints object to reference hints like the display label, format mask, tooltip, etc.

Now you can use this understanding to get runtime meta info about view object or entity object e.g. if i want to find whether a ViewObject is readonly non entity based object or not. i can find it by:

• isFullSql() is true

  This method returns true if the view object's SQL query is completely specified by the developer, as opposed to having the select list derived automatically based on the participating entity usages.

• getEntityDefs() is null

  This method returns an array of EntityDefImpl objects representing the view object's entity usages. If it returns null, then the view object has no entity usages.

Programmatically Navigating to another page in adf / jsf

Here is the sample code which can be used to programmatically navigating to another page in jsf or adf

FacesContext fctx = FacesContext.getCurrentInstance();
Application application = fctx.getApplication();
NavigationHandler navHandler = application.getNavigationHandler();
navHandler.handleNavigation(fctx,null, "name of navigation case");

Doing some work before showing Popup in ADF

Here is the way to do any processing before calling popup. First of all create a method in backing bean and assign this to action of "commandButton" or "commandLink". Sample signature for you method is as follows:

public void myMethod()
{
/**
* Place your processing logic here and then call showPoup method
**/
showPopup(popupId);
}

Signature of showPopup is:

public static void showPopup(String popupId)
{
FacesContext context = FacesContext.getCurrentInstance();

ExtendedRenderKitService extRenderKitSrvc =
Service.getRenderKitService(context, ExtendedRenderKitService.class);
extRenderKitSrvc.addScript(context,
"AdfPage.PAGE.findComponent('" + popupId + "').show();");
}

Pros and Cons of JDeveloper 11g and ADF from begginers Point of View

I have started to use JDeveloper 11g and ADF for one of my enterprise level project. I didn't use any part of ADF before. Its now one month and i want to share with world what i found in ADF with JDeveloper 11g.

Pros:
- It is based on MVC pattern and cleanly separates your business logic from presentation layer.
- It has built in support for AJAX
- Very rapid development because most of the development one can do declaratively by just drag and drop components on pages and like that
- Most important and exciting feature from me was very good support of LOV. LOV is required in almost every business application and with ADF i don't have to do any code for LOV just a query and some very small configurations and that's it.
- Rich Tables supporting LOV, combo box and others.
- It provides good hooks to develop own framework or utility classes to suit development e.g. I want to extend all entities from my own class and i can do it very easily.
- One of the unique feature of ADF 11g is ADF Task flow which faciliates developer to define reusable navigation and avoid cluttering of all navigation rules in one file which happens in JSF

Cons
Now we discuss cons of ADF and JDeveloper 11g
- JDeveloper is buggy and crashes many times espeically when one does refactoring or deleting some resources
- You will have to spend good time to learn ADF if you didn't have prior experience with Oracle technologies
- Query component in ADF Faces which is used to build criteria does not have option to change the layout of fields like grouping etc.
- LOV which are generated are also buggy. I am still facing one problem and no one still gave me solution for that.
- You will have to do lot of hit and trials to understand the behaviour of layout components

ADF Error timezone region not found

When i deploy/run adf applications, i receive error:

timezone region  not found

In order to solve this, right click on Model project and select Project properties. In "Run/Debug/Profile" select "Edit" in "Run Configurations" and add "-Duser.timezone=UTC" in JavaOptions. Repeat same steps for ViewController Project.