Sunday, August 30, 2009

Showing a Confirmation Message

Faces Message can have there severity specified. Inbuilt severity are for fatal,error,warning and information.

To get a confirmation message we can use FacesMessageUtils.getConfirmationMessage which takes a FacesMessage as input.

This is the managed bean code

public void onClick(ActionEvent actionEvent) {
// Add event code here...
String sb = "My Confirmation Message";
FacesContext ctx = FacesContext.getCurrentInstance();
FacesMessage msg =
FacesMessageUtils.getConfirmationMessage(new FacesMessage(sb.toString()));
ctx.addMessage(null, msg);

I have bounded the Action listener of command button to above code

Now lets see if you want to format the message, how to do it.

public void onClick(ActionEvent actionEvent) {
// Add event code here...
StringBuilder sb = new StringBuilder();
sb.append(" <br> is cool! </br>");
sb.append("<hr> So is <b> Jdevloper</b>");
FacesContext ctx = FacesContext.getCurrentInstance();
FacesMessage msg =
FacesMessageUtils.getConfirmationMessage(new FacesMessage(sb.toString()));
ctx.addMessage(null, msg);


Integrated WLS Server Instance Conflict

If Integrated WLS server in jdeveloper is not shutdown properly, then sometimes you see the following error message.

To resolve the issue , simply end java.exe process from task Manager -> process tab

A List of TODO's

How often in development , do we leave things for future, when we intend to visit back, but alas we forget.

Like I Need to do a NPE checking, Handle the error, Remove SOP, Make it robust etc.

We might write comments for that in the source code, but again if we don't go through the code diligently either we might not find them, or oops! forgot.

Jdev comes with a very good utility called TODO.Have been using this in my current project a lot where requirements are developing/changing by the day.

You can create a TODO , just by typing TODO after // in source file. Later through Task window, you can view all the TODO's in your project/application. TODO's can also be created for entire project or application.

You can view tasks window through View-->Tasks and it would list all the TODO's in your application.

Thursday, August 20, 2009

ADF Table and QBE

Query By Example(QBE) is a powerful feature in ADF, using which user can filter results at runtime.

In this article , we'll see few cases on how to use QBE

An entity, view object and Am based on HR schema, Employee is created.

Create a jsf page, and insert a panel collection inside jsp root tag.

Inside the panel collection drop the View Object from data control as a table.

To turn on QBE, select the check the filter option.

Select the table in structure window, go to properties panel, and from the Appearance section, for the property "Filter visible" , turn it to false.

Run the page. You'll observe a QBE(filter) icon, at the top in toolbar.
Click on it and filterable fields will appear over each column. Key in your filter criteria and hit enter. Table results get filtered.

Explore the table properties, and you'll see FilterModel and QueryListener properties set, which are used internally by the framework to filter results.

Open the pagedef for the above page, and you'll notice a Search Region under the executables which Filter Model and QueryListener points too.

Now say, when user visits the page for the first time, he wants to see only those employee whose salary is greater then 6000.

For this, we need to create a new view criteria in the VO(with Salary > 6000). Mark the auto execute property of the view criteria to true.

Open the above Search Region under the executables in page def, and for the Criteria Attribute, set the value to the name of the view criteria created above.

Now , when you run the page, you'll see all employees with salary greater then 6000 automatically filtered, when you land on the page. You can create any such complex criteria, and filter the table results.

Now lets suppose, you want a choice list at the top, with all departments, and you want to give user a choice to filter using that choice list.

We can use QBE feature to implement this pattern.

First lets create a JobsVO( Read only VO, based on a SQL query).
My query looks like this.

ORDER BY Job_id nulls FIRST

I have a null option, so that i can filter for all departments, when user selects a blank value.

Attach this Vo(JobVO) in AM, and then through data control, drop this view in Panel Collection toolbar facet as a choice list.

For the choicelist, set AutoSubmit to true. Give a proper label,set Required property to false.
Under Adavanced section, you'll find ValueChangeListener. Bind the valuechangeListener to a method in managed bean.

Also bind the table to managed bean.

public void onJobChange(ValueChangeEvent valueChangeEvent) {
// Add event code here...
FacesContext fc = FacesContext.getCurrentInstance();
String job =
(String)fc.getApplication().evaluateExpressionGet(fc, "#{bindings.JobId.inputValue}",
RichTable tbl = this.getMyTable();
FilterableQueryDescriptor filterQD =
Map filterCriteria = filterQD.getFilterCriteria();
if (filterCriteria == null) {
filterCriteria = new HashMap<String, Object>();
filterCriteria.put("JobId", job);
QueryEvent queryEvent = new QueryEvent(tbl, filterQD);
MethodBinding queryListener = tbl.getQueryListener();
queryListener.invoke(fc, new Object[] { queryEvent });


Choice list returns index, if i directly access, the valueChangeEvent.getNewValue()
However we want the real Job and not index. Therefore the easiest way to get is through attribute binding.

For this first i created a Attribute Binding in page def, for the attribute JobId from JobsVO

Now, since ValueChangeListener is fired before model gets a chance to update its value to the new Job selected, therefore as a first line in method above, we are updating the model, with selected value.

Once this is done, we retrieve the selected job though the EL expression . Now we get hold of Query Descriptor , and in the filter criteria, set the appropriate field and its value. After which we fire the Query event.

Table is filtered and returns the rows with selected job only.

Uploaded project is at

Run the untitled1.jspx and experiment.

Sunday, August 16, 2009

Quick Byte Series - Structural Patterns

Continuining with the Quick Byte Series, Lets go through the structural patterns :

Adaptor : converts the existing interface to a new interface that provides compatibility between unrelated classes and can act as wrapper

Bridge : Decouple an abstraction from its implementation so that the two can vary independently.

Composite : Compose objects into tree structures to represent part-whole hierarchies.

Decorator : Attach additional responsibilities to an object dynamically keeping the same interface. Decorators provide a flexible alternative to subclassing for extending functionality.

Facade : Make a complex system simpler by providing a general interface.

Flyweight : Use sharing to support large numbers of fine-grained objects efficiently.

Proxy : Provide a placeholder for another object to control access to it.

Thursday, August 13, 2009

Quick Byte Series - Creational Patterns

We starting a series of Quick Byte sessions where in we will try to get a quick grab of things we already know or atleast are supposed to know. In this first post, Lets get a quick view of Creational Patterns (the ones where in we are more concerned about object creation) :

Singleton : Provides single instance of the class, which is accessible throught out the application. We need to ensure that this is thread safe.

Factory Method : Provides an abstraction and let subclasses decide which class needs to be instantiated based on the provided parameters.

Abstract Factory Method : Layer above the Factory menthod. While in Factory method, we are covering for single object – here in Abstract Factory Method, we cater for multiple products.

Builder : Builder Pattern is used for creating a complex object from simple objects in a step-by-step process.

Prototype : When object creation comes with a cost, Prototype pattern comes to the rescue where in objects are cloned.