应用JSF技术开发(Developing with JavaServer Faces Technology:chapter11)《注：未完成》

应用JSF技术开发

Chapter 10 演示了页面作者可以通过页面上的组件标签和core标签将组件和服务器端对象绑定。应用开发者的职责就是编写JSF应用的服务器端对象。这些对象包括后台beans，转换器，事件处理和验证器。这一章用Duke的书店应用(see The Example JavaServer Faces Application, page 308)讲解应用开发者的职责包括：

对后台bean编程

本地化应用程序

创建用户定义转换器和验证器

实现事件监听器

编写后台bean方法来执行导航处理，数据验证和事件处理

编写bean属性

已在page295解释过，一个后台bean属性可以被和以下条目绑定：

一个组件值

一个组件实例

一个转换器实现

一个监听器实现

一个验证器实现

这些属性遵循了JavaBeans组件的规则(see JavaBeans Components, page 131).
UI组件标签用值attribute把其值绑定到一个属性，并且，把组件实例绑定attribute。具体介绍Binding Component Values and Instances to External Data Sources (page 361).同样，所有的转换器，监听器，验证器标签用绑定的attribute来把他们的实现和后台bean属性绑定，具体解释 Binding Converters, Listeners, and Validators to Backing Bean Properties (page 367).
把组件值和后台bean属性绑定，后台bean属性必须和组件值的类型相匹配。举例，如果后台bean属性需要绑定到一个

UISelectBoolean

值，则这个bean的相应属性应该接受boolean或Boolean包装类实例作为返回值。
为了绑定一个组件实例，bean的属性必须和组件类型匹配。举例，如果一个后台bean属性需要绑定到

UISelectBoolean

实例，则其属性就应该接受并返回

UISelectBoolean

。

同样，为了绑定一个转换器，监听器，或验证器实现到一个属性，这个属性必须接受并返回同样类型的转换器，监听器或验证器对象。举例，如果你用

convertDateTime

标签绑定

DateTime

转换器到一个属性，则这个属性必须接受并返回

DateTime

实例。
下面的章节介绍了如何编写能被绑定到组件值的属性，组件属性描述Adding UI Components to a Page Using the HTML Component Tags (page 316), and to converter, listener, and validator implementations.

Writing Properties Bound to Component Values

To write a backing bean property bound to a component's value, you must know the types that the component's value can be so that you can make the property match the type of the component's value.

Table 11-1 lists all the component classes described in Adding UI Components to a Page Using the HTML Component Tags (page 316) and the acceptable types of their values.

When page authors bind components to properties using the

value

attributes of the component tags, they need to ensure that the corresponding properties match the types of the components' values.

Table 11-1 Acceptable Types of Component Values

Component	Acceptable Types of Component Values
UIInput , UIOutput , UISelectItem , UISelectOne	Any of the basic primitive and numeric types or any Java programming language object type for which an appropriate Converter implementation is available.
UIData	array of beans, List of beans, single bean, java.sql.ResultSet, javax.servlet.jsp.jstl.sql.Result , javax.sql.RowSet .
UISelectBoolean	boolean or Boolean .
UISelectItems	java.lang.String, Collection, Array, Map .
UISelectMany	array or List. Elements of the array or List can be any of the standard types.

UIInput and UIOutput Properties

The following tag binds the

name

component to the

name

property of

CashierBean

.

<h:inputText id="name" size="50"
value="#{cashier.name}"
required="true">
<f:valueChangeListener
type="com.sun.bookstore6.listeners.NameChanged" />
</h:inputText>

Here is the bean property bound to the

name

component:

protected String name = null;
public void setName(String name) {
this.name = name;
}
public String getName() {
return this.name;
}

[/code]

As Using the Standard Converters (page 349) describes, to convert the value of a

UIInput

or

UIOutput

component, you can either apply a converter or create the bean property bound to the component with the desired type. Here is the example tag explained in Using DateTimeConverter (page 352) that displays the date books will be shipped:

<h:outputText value="#{cashier.shipDate}">
<f:convertDateTime dateStyle="full" />
</h:outputText>

The application developer must ensure that the property bound to the component represented by this tag has a type of

java.util.Date

. Here is the

shipDate

property in

CashierBean

:

protected Date shipDate;
public Date getShipDate() {
return this.shipDate;
}
public void setShipDate(Date shipDate) {
this.shipDate = shipDate;
}

[/code]

See Binding Component Values and Instances to External Data Sources (page 361) for more information on applying a

Converter

implementation.

UIData Properties

UIData

components must be bound to one of the types listed in Table 11-1. The

UIData

component from the

bookshowcart.jsp

page of the Duke's Bookstore example is discussed in the section Using Data-Bound Table Components (page 329). 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 the

ShoppingCart

bean. The

ShoppingCart

bean maintains a map of

ShoppingCartItem

beans.

The

getItems

method from

ShoppingCart

populates a

List

with

ShoppingCartItem

instances that are saved in the items map from when the customer adds books to the cart:

public synchronized List getItems() {
List results = new ArrayList();
results.addAll(this.items.values());
return results;
}

All the components contained in the

UIData

component are bound to the properties of the

ShoppingCart

bean that is bound to the entire

UIData

component. For example, here is the

outputText

tag that displays the book title in the table:

<h:commandLink action="#{showcart.details}">
<h:outputText value="#{item.item.title}"/>
</h:commandLink>

The book title is actually a hyperlink to the

bookdetails.jsp

page. The

outputText

tag uses the value expression

#{item.item.title}

to bind its

UIOutput

component to the

title

property of the

Book

bean. The first

item

in the expression is the

ShoppingCartItem

instance that the

dataTable

tag is referencing while rendering the current row. The second

item

in the expression refers to the

item

property of

ShoppingCartItem

, which returns a

Book

bean. 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

bean:

private String title = null;
public String getTitle() {
return this.title;
}
public void setTitle(String title) {
this.title=title;
}

UISelectBooleanProperties

Properties that hold the

UISelectBoolean

component's data must be of

boolean

or

Boolean

type. The example

selectBooleanCheckbox

tag from the section Rendering Components for Selecting One Value (page 337) binds a component to a property. Here is an example that binds a component value to a 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:

protected boolean receiveEmails = false;
...
public void setReceiveEmails(boolean receiveEmails) {
this.receiveEmails = receiveEmails;
}
public boolean getReceiveEmails() {
return receiveEmails;
}

[/code]

UISelectMany Properties

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.

Here is the example

selectManyCheckbox

tag from Rendering Components for Selecting Multiple Values (page 339):

<h:selectManyCheckbox
id="newsletters"
layout="pageDirection"
value="#{cashier.newsletters}">
<f:selectItems value="#{newsletters}"/>
</h:selectManyCheckbox>

Here is a bean property that maps to the

value

of this

selectManyCheckbox

example:

protected String newsletters[] = new String[0];

public void setNewsletters(String newsletters[]) {
this.newsletters = newsletters;
}
public String[] getNewsletters() {
return this.newsletters;
}

As explained in the section Rendering Components for Selecting Multiple Values (page 339), the

UISelectItem

and

UISelectItems

components are used to represent all the values in a

UISelectMany

component. See UISelectItem Properties and UISelectItemsProperties for information on how to write the bean properties for the

UISelectItem

and

UISelectItems

components.

UISelectOne Properties

UISelectOne

properties accept the same types as

UIInput

and

UIOutput

properties. This is 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 the example

selectOneMenu

tag from Displaying a Menu Using the selectOneMenu Tag (page 338):

<h:selectOneMenu   id="shippingOption"
required="true"
value="#{cashier.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 property corresponding to this tag:

protected 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.

As explained in the section Displaying a Menu Using the selectOneMenu Tag (page 338), the

UISelectItem

and

UISelectItems

components are used to represent all the values in a

UISelectOne

component. See UISelectItem Properties and UISelectItemsProperties for information on how to write the backing bean properties for the

UISelectItem

and

UISelectItems

components.

UISelectItem Properties

A

UISelectItem

component represents one value in a set of values in a

UISelectMany

or

UISelectOne

component. The backing bean property that a

UISelectItem

component is bound to must be of type

SelectItem

. A

SelectItem

object is composed of an

Object

representing the value, along with two

Strings

representing the label and description of the

SelectItem

object.

The Duke's Bookstore application does not use any

UISelectItem

components whose values are bound to backing beans. The example

selectOneMenu

tag from Displaying a Menu Using the selectOneMenu Tag (page 338) contains

selectItem

tags that set the values of the list of items in the page. Here is an example 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;
}

UISelectItemsProperties

UISelectItems

components are children of

UISelectMany

and

UISelectOne

components. Each

UISelectItems

component is composed of either a set of

SelectItem

instances or a set of

SelectItemGroup

instances. As described in Using the selectItems Tag (page 342), a

SelectItemGroup

is composed of a set of

SelectItem

instances. This section describes how to write the properties for

selectItems

tags containing

SelectItem

instances and for

selectItems

tags containing

SelectItemGroup

instances.

Properties for SelectItems Composed of SelectItem Instances

Using the selectItems Tag (page 342) describes how the newsletters list of the Duke's Bookstore application is populated using the application configuration resource file. You can also populate the

SelectItems

with

SelectItem

instances programmatically in the backing bean. This section explains how to do this.

In your backing bean, you create a list that is bound to the

SelectItem

component. Then you define a set of

SelectItem

objects, set their values, and populate the list with the

SelectItem

objects. Here is an example code snippet that shows how to create a

SelectItems

property:

import javax.faces.component.SelectItem;
...
protected ArrayList options = null;
protected SelectItem newsletter0 =
new SelectItem("200", "Duke's Quarterly", "");
...
//in constructor, populate the list
options.add(newsletter0);
options.add(newsletter1);
options.add(newsletter2);
...
public SelectItem getNewsletter0(){
return newsletter0;
}

void setNewsletter0(SelectItem firstNL) {
newsletter0 = firstNL;
}
// Other SelectItem properties

public Collection[] getOptions(){
return options;
}
public void setOptions(Collection[] options){
this.options = new ArrayList(options);
}

The code first initializes

options

as a list. Each newsletter property is defined with values. Then, each newsletter

SelectItem

is added to the list. Finally, the code includes the obligatory

setOptions

and

getOptions

accessor methods.

Properties for SelectItems Composed of SelectItemGroup Instances

The preceding section explains how to write the bean property for a

SelectItems

component composed of

SelectItem

instances. This section explains how to change the example property from the preceding section so that the

SelectItems

is composed of

SelectItemGroup

instances.

Let's separate the newsletters into two groups: One group includes Duke's newsletters, and the other group includes the Innovator's Almanac and Random Ramblings newsletters.

In your backing bean, you need a list that contains two

SelectItemGroup

instances. Each

SelectItemGroup

instance contains two

SelectItem

instances, each representing a newsletter:

import javax.faces.model.SelectItemGroup;
...
private ArrayList optionsGroup = null;

optionsGroup = new ArrayList(2);

private static final SelectItem options1[] = {
new SelectItem("200", "Duke's Quarterly", "");
new SelectItem("202",
"Duke's Diet and Exercise Journal", "");
};
private static final SelectItem options2[] = {
new SelectItem("201", "Innovator's Almanac", "");
new SelectItem("203", "Random Ramblings", "");
};

SelectItemGroup group1 =
new SelectItemGroup("Duke's", null, true, options1);
SelectItemGroup group2 =
new SelectItemGroup("General Interest", null, true,
options2);

optionsGroup.add(group1);
optionsGroup.add(group2);
...
public Collection getOptionsGroup() {
return optionsGroup;
}
public void setOptionsGroup(Collection newGroupOptions) {
optionsGroup = new ArrayList(newGroupOptions);
}

The code first initializes

optionsGroup

as a list. The

optionsGroup

list contains two

SelectItemGroup

objects. Each object is initialized with the label of the group appearing in the list or menu; a value; a Boolean indicating whether or not the label is disabled; and an array containing two

SelectItem

instances. Then each

SelectItemGroup

is added to the list. Finally, the code includes the

setOptionsGroup

and

getOptionsGroup

accessor methods so that the tag can access the values. The

selectItems

tag references the

optionsGroup

property to get the

SelectItemGroup

objects for populating the list or menu on the page.

Writing Properties Bound to Component Instances

A property bound to a component instance returns and accepts a component instance rather than a component value. Here are the tags described in Binding a Component Instance to a Bean Property (page 366) that bind components to backing bean properties:

<h:selectBooleanCheckbox
id="fanClub"
rendered="false"
binding="#{cashier.specialOffer}" />
<h:outputLabel for="fanClub"
rendered="false"
binding="#{cashier.specialOfferText}"  >
<h:outputText id="fanClubLabel"
value="#{bundle.DukeFanClub}" />
</h:outputLabel>

As Binding a Component Instance to a Bean Property (page 366) explains, the

selectBooleanCheckbox

tag renders a checkbox and binds the

fanClub

UISelectBoolean

component to the

specialOffer

property of

CashierBean

. The

outputLabel

tag binds the

fanClubLabel

component (which represents the checkbox's label) to the

specialOfferText

property of

CashierBean

. If the user orders more than $100 (or 100 euros) worth of books and clicks the Submit button, the

submit

method of

CashierBean

sets both components'

rendered

properties to

true

, causing the checkbox and label to display when the page is rerendered.

Because the components corresponding to the example tags are bound to the backing bean properties, these properties must match the components' types. This means that the

specialOfferText

property must be of

UIOutput

type, and the

specialOffer

property must be of

UISelectBoolean

type:

UIOutput specialOfferText = null;

public UIOutput getSpecialOfferText() {
return this.specialOfferText;
}
public void setSpecialOfferText(UIOutput specialOfferText) {
this.specialOfferText = specialOfferText;
}

UISelectBooleanspecialOffer = null;

public UISelectBooleangetSpecialOffer() {
return this.specialOffer;
}
public void setSpecialOffer(UISelectBooleanspecialOffer) {
this.specialOffer = specialOffer;
}  

See Backing Beans (page 295) for more general information on component binding.

See Referencing a Method That Performs Navigation (page 370) for information on how to reference a backing bean method that performs navigation when a button is clicked.

See Writing a Method to Handle Navigation for more information on writing backing bean methods that handle navigation.

Writing Properties Bound to Converters, Listeners, or Validators

All of the standard converter, listener, and validator tags that are included with JavaServer Faces technology support binding attributes that allow page authors to bind converter, listener, or validator implementations to backing bean properties.

The following example from Binding Converters, Listeners, and Validators to Backing Bean Properties (page 367) shows a standard

convertDateTime

tag using a value expression with its

binding

attribute to bind the

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([code]"EEEEEEEE, MMM dd, yyyy");

this.convertDate = convertDate;
} [/code]

因为converter被绑定到后台bean属性上，后台bean属性可以修改converter的属性或者给它添加新功能。在前面的例子里，converter会解析用户输入数据将其转化成Date对象。

The backing bean properties that are bound to validator or listener implementations are written in the same way and have the same general purpose.