The Java EE 7 Tutorial
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12.2 Writing Bean Properties
As explained in Managed Beans in JavaServer Faces Technology, a managed bean property can be bound to one of the following items:
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A component value
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A component instance
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A converter implementation
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A listener implementation
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A validator implementation
These properties follow the conventions of JavaBeans components (also called beans). For more information on JavaBeans components, see the JavaBeans Tutorial at http://docs.oracle.com/javase/tutorial/javabeans/index.html.
The component's tag binds the component's value to a managed bean property by using its value attribute and binds the component's instance to a managed bean property by using its binding attribute. Likewise, all the converter, listener, and validator tags use their binding attributes to bind their associated implementations to managed bean properties. See Binding Component Values and Instances to Managed Bean Properties and Binding Converters, Listeners, and Validators to Managed Bean Properties for more information.
To bind a component's value to a managed bean property, the type of the property must match the type of the component's value to which it is bound. For example, if a managed bean property is bound to a UISelectBoolean component's value, the property should accept and return a boolean value or a Boolean wrapper Object instance.
To bind a component instance to a managed bean property, the property must match the type of component. For example, if a managed bean property is bound to a UISelectBoolean instance, the property should accept and return a UISelectBoolean value.
Similarly, to bind a converter, listener, or validator implementation to a managed bean property, the property must accept and return the same type of converter, listener, or validator object. For example, if you are using the convertDateTime tag to bind a javax.faces.convert.DateTimeConverter to a property, that property must accept and return a DateTimeConverter instance.
The rest of this section explains how to write properties that can be bound to component values, to component instances for the component objects described in Adding Components to a Page Using HTML Tag Library Tags, and to converter, listener, and validator implementations.
12.2.1 Writing Properties Bound to Component Values
To write a managed bean property that is bound to a component's value, you must match the property type to the component's value.
Table 12-1 lists the javax.faces.component classes and the acceptable types of their values.
Table 12-1 Acceptable Types of Component Values
| Component Class | Acceptable Types of Component Values |
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Any of the basic primitive and numeric types or any Java programming language object type for which an appropriate |
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When they bind components to properties by using the value attributes of the component tags, page authors need to ensure that the corresponding properties match the types of the components' values.
12.2.1.1 UIInput and UIOutput Properties
The UIInput and UIOutput component classes are represented by the component tags that begin with h:input and h:output, respectively (for example, h:inputText and h:outputText).
In the following example, an h:inputText tag binds the name component to the name property of a managed bean called CashierBean.
<h:inputText id="name"
size="30"
value="#{cashierBean.name}"
...>
</h:inputText>
The following code snippet from the managed bean CashierBean shows the bean property type bound by the preceding component tag:
protected String name = null;
public void setName(String name) {
this.name = name;
}
public String getName() {
return this.name;
}
As described in Using the Standard Converters, to convert the value of an input or output component you can either apply a converter or create the bean property bound to the component with the matching type. Here is the example tag, from Using DateTimeConverter, that displays the date on which items will be shipped.
<h:outputText value="#{cashierBean.shipDate}">
<f:convertDateTime type="date" dateStyle="full" />
</h:outputText>
The bean property represented by this tag must have a type of java.util.Date. The following code snippet shows the shipDate property, from the managed bean CashierBean, that is bound by the tag's value in the preceding example:
private Date shipDate;
public Date getShipDate() {
return this.shipDate;
}
public void setShipDate(Date shipDate) {
this.shipDate = shipDate;
}
12.2.1.2 UIData Properties
The UIData component class is represented by the h:dataTable component tag.
UIData components must be bound to one of the managed bean property types listed in Table 12-1. Data components are discussed in Using Data-Bound Table Components. Here is part of the start tag of dataTable from that section:
<h:dataTable id="items"
...
value="#{cart.items}"
...
var="item">
The value expression points to the items property of a shopping cart bean named cart. The cart bean maintains a map of ShoppingCartItem beans.
The getItems method from the cart bean populates a List with ShoppingCartItem instances that are saved in the items map when the customer adds books to the cart, as shown in the following code segment:
public synchronized List<ShoppingCartItem> getItems() {
List<ShoppingCartItem> results = new ArrayList<ShoppingCartItem>();
results.addAll(this.items.values());
return results;
}
All the components contained in the UIData component are bound to the properties of the cart bean that is bound to the entire UIData component. For example, here is the h:outputText tag that displays the book title in the table:
<h:commandLink action="#{showcart.details}">
<h:outputText value="#{item.item.title}"/>
</h:commandLink>
The title is actually a link to the bookdetails.xhtml page. The h:outputText tag uses the value expression #{item.item.title} to bind its UIOutput component to the title property of the Book entity. The first item in the expression is the ShoppingCartItem instance that the h:dataTable tag is referencing while rendering the current row. The second item in expression refers to the item property of ShoppingCartItem, which returns an Object (in this case, a Book). The title part of the expression refers to the title property of Book. The value of the UIOutput component corresponding to this tag is bound to the title property of the Book entity:
private String title;
...
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
12.2.1.3 UISelectBoolean Properties
The UISelectBoolean component class is represented by the component tag h:selectBooleanCheckbox.
Managed bean properties that hold a UISelectBoolean component's data must be of boolean or Boolean type. The example selectBooleanCheckbox tag from the section Displaying Components for Selecting One Value binds a component to a property. The following example shows a tag that binds a component value to a boolean property:
<h:selectBooleanCheckbox title="#{bundle.receiveEmails}"
value="#{custFormBean.receiveEmails}">
</h:selectBooleanCheckbox>
<h:outputText value="#{bundle.receiveEmails}">
Here is an example property that can be bound to the component represented by the example tag:
private boolean receiveEmails = false;
...
public void setReceiveEmails(boolean receiveEmails) {
this.receiveEmails = receiveEmails;
}
public boolean getReceiveEmails() {
return receiveEmails;
}
12.2.1.4 UISelectMany Properties
The UISelectMany component class is represented by the component tags that begin with h:selectMany (for example, h:selectManyCheckbox and h:selectManyListbox).
Because a UISelectMany component allows a user to select one or more items from a list of items, this component must map to a bean property of type List or array. This bean property represents the set of currently selected items from the list of available items.
The following example of the selectManyCheckbox tag comes from Displaying Components for Selecting Multiple Values:
<h:selectManyCheckbox id="newslettercheckbox"
layout="pageDirection"
value="#{cashierBean.newsletters}">
<f:selectItems value="#{cashierBean.newsletterItems}"/>
</h:selectManyCheckbox>
Here is the bean property that maps to the value of the selectManyCheckbox tag from the preceding example:
private String[] newsletters;
public void setNewsletters(String[] newsletters) {
this.newsletters = newsletters;
}
public String[] getNewsletters() {
return this.newsletters;
}
The UISelectItem and UISelectItems components are used to represent all the values in a UISelectMany component. See UISelectItem Properties and UISelectItems Properties for information on writing the bean properties for the UISelectItem and UISelectItems components.
12.2.1.5 UISelectOne Properties
The UISelectOne component class is represented by the component tags that begin with h:selectOne (for example, h:selectOneRadio and h:selectOneListbox).
UISelectOne properties accept the same types as UIInput and UIOutput properties, because a UISelectOne component represents the single selected item from a set of items. This item can be any of the primitive types and anything else for which you can apply a converter.
Here is an example of the h:selectOneMenu tag from Displaying a Menu Using the h:selectOneMenu Tag:
<h:selectOneMenu id="shippingOption"
required="true"
value="#{cashierBean.shippingOption}">
<f:selectItem itemValue="2"
itemLabel="#{bundle.QuickShip}"/>
<f:selectItem itemValue="5"
itemLabel="#{bundle.NormalShip}"/>
<f:selectItem itemValue="7"
itemLabel="#{bundle.SaverShip}"/>
</h:selectOneMenu>
Here is the bean property corresponding to this tag:
private String shippingOption = "2";
public void setShippingOption(String shippingOption) {
this.shippingOption = shippingOption;
}
public String getShippingOption() {
return this.shippingOption;
}
Note that shippingOption represents the currently selected item from the list of items in the UISelectOne component.
The UISelectItem and UISelectItems components are used to represent all the values in a UISelectOne component. This is explained in Displaying a Menu Using the h:selectOneMenu Tag.
For information on how to write the managed bean properties for the UISelectItem and UISelectItems components, see UISelectItem Properties and UISelectItems Properties.
12.2.1.6 UISelectItem Properties
A UISelectItem component represents a single value in a set of values in a UISelectMany or a UISelectOne component. A UISelectItem component must be bound to a managed bean property of type javax.faces.model.SelectItem. A SelectItem object is composed of an Object representing the value along with two Strings representing the label and the description of the UISelectItem object.
The example selectOneMenu tag from UISelectOne Properties contains selectItem tags that set the values of the list of items in the page. Here is an example of a bean property that can set the values for this list in the bean:
SelectItem itemOne = null;
SelectItem getItemOne(){
return itemOne;
}
void setItemOne(SelectItem item) {
itemOne = item;
}
12.2.1.7 UISelectItems Properties
UISelectItems components are children of UISelectMany and UISelectOne components. Each UISelectItems component is composed of a set of either UISelectItem instances or any collection of objects, such as an array, a list, or even POJOs.
The following code snippet from CashierBean shows how to write the properties for selectItems tags containing SelectItem instances.
private String[] newsletters;
private static final SelectItem[] newsletterItems = {
new SelectItem("Duke's Quarterly"),
new SelectItem("Innovator's Almanac"),
new SelectItem("Duke's Diet and Exercise Journal"),
new SelectItem("Random Ramblings")
};
...
public void setNewsletters(String[] newsletters) {
this.newsletters = newsletters;
}
public String[] getNewsletters() {
return this.newsletters;
}
public SelectItem[] getNewsletterItems() {
return newsletterItems;
}
Here, the newsletters property represents the SelectItems object, whereas the newsletterItems property represents a static array of SelectItem objects. The SelectItem class has several constructors; in this example, the first argument is an Object representing the value of the item, whereas the second argument is a String representing the label that appears in the UISelectMany component on the page.
12.2.2 Writing Properties Bound to Component Instances
A property bound to a component instance returns and accepts a component instance rather than a component value. The following components bind a component instance to a managed bean property:
<h:selectBooleanCheckbox id="fanClub"
rendered="false"
binding="#{cashierBean.specialOffer}" />
<h:outputLabel for="fanClub"
rendered="false"
binding="#{cashierBean.specialOfferText}"
value="#{bundle.DukeFanClub}" />
</h:outputLabel>
The selectBooleanCheckbox tag renders a check box and binds the fanClub UISelectBoolean component to the specialOffer property of CashierBean. The outputLabel tag binds the value of the value attribute, which represents the check box's label, to the specialOfferText property of CashierBean. If the user orders more than $100 worth of books and clicks the Submit button, the submit method of CashierBean sets both components' rendered properties to true, causing the check box and label to display when the page is re-rendered.
Because the components corresponding to the example tags are bound to the managed bean properties, these properties must match the components' types. This means that the specialOfferText property must be of type UIOutput, and the specialOffer property must be of type UISelectBoolean:
UIOutput specialOfferText = null;
UISelectBoolean specialOffer = null;
public UIOutput getSpecialOfferText() {
return this.specialOfferText;
}
public void setSpecialOfferText(UIOutput specialOfferText) {
this.specialOfferText = specialOfferText;
}
public UISelectBoolean getSpecialOffer() {
return this.specialOffer;
}
public void setSpecialOffer(UISelectBoolean specialOffer) {
this.specialOffer = specialOffer;
}
For more general information on component binding, see Managed Beans in JavaServer Faces Technology.
For information on how to reference a managed bean method that performs navigation when a button is clicked, see Referencing a Method That Performs Navigation.
For more information on writing managed bean methods that handle navigation, see Writing a Method to Handle Navigation.
12.2.3 Writing Properties Bound to Converters, Listeners, or Validators
All the standard converter, listener, and validator tags included with JavaServer Faces technology support binding attributes that allow you to bind converter, listener, or validator implementations to managed bean properties.
The following example shows a standard convertDateTime tag using a value expression with its binding attribute to bind the javax.faces.convert.DateTimeConverter instance to the convertDate property of LoginBean:
<h:inputText value="#{loginBean.birthDate}">
<f:convertDateTime binding="#{loginBean.convertDate}" />
</h:inputText>
The convertDate property must therefore accept and return a DateTimeConverter object, as shown here:
private DateTimeConverter convertDate;
public DateTimeConverter getConvertDate() {
...
return convertDate;
}
public void setConvertDate(DateTimeConverter convertDate) {
convertDate.setPattern("EEEEEEEE, MMM dd, yyyy");
this.convertDate = convertDate;
}
Because the converter is bound to a managed bean property, the managed bean property can modify the attributes of the converter or add new functionality to it. In the case of the preceding example, the property sets the date pattern that the converter uses to parse the user's input into a Date object.
The managed bean properties that are bound to validator or listener implementations are written in the same way and have the same general purpose.
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