Writing a Method to Handle Navigation

A backing bean method that handles navigation processing, called an action method, must be a public method that takes no parameters and returns an Object, which is the logical outcome that the navigation system uses to determine the page to display next. This method is referenced using the component tag’s action attribute.

The following action method is from a backing bean named CashierBean, which is invoked when a user clicks the Submit button on the page. If the user has ordered more than $100 worth of books, this method sets the rendered properties of the fanClub and specialOffer components to true, causing them to be displayed on the page the next time that page is rendered.

After setting the components’ rendered properties to true, this method returns the logical outcome null. This causes the JavaServer Faces implementation to re-render the page without creating a new view of the page, retaining the customer’s input. If this method were to return purchase which is the logical outcome to use to advance to a payment page, the page would re-render without retaining the customer’s input.

If the user does not purchase more than $100 worth of books or the thankYou component has already been rendered, the method returns receipt.The JavaServer Faces implementation loads the page after this method returns.

public String submit() {
    ...
    if(cart().getTotal() > 100.00 &&
         !specialOffer.isRendered())
    {
        specialOfferText.setRendered(true);
        specialOffer.setRendered(true);
        return null;
    } else if (specialOffer.isRendered() &&
         !thankYou.isRendered()){
        thankYou.setRendered(true);
        return null;
    } else {
        clear();
        return ("receipt");
    }
}

Typically, an action method will return a String outcome, as shown in the previous example. Alternatively, you can define an Enum class that encapsulates all possible outcome strings, and then make an action method return an enum constant, which represents a particular String outcome defined by the Enum class. In this case, the value returned by a call to the Enum class’s toString method must match that specified by the from-outcome element in the appropriate navigation rule configuration defined in the application configuration file.

The following example uses an Enum class to encapsulate all logical outcomes:

public enum Navigation  {
    main, accountHist, accountList, atm, atmAck, transferFunds,
     transferAck, error
}

When an action method returns an outcome, it uses the dot notation to reference the outcome from the Enum class:

public Object submit(){
    ...
    return Navigation.accountHist;
}

The section Referencing a Method That Performs Navigation explains how a component tag references this method. The section Writing Properties Bound to Component Instances discusses how to write the bean properties to which the components are bound.