Combo Box

Creates a drop down list from which a user may select one of multiple choices. The list of choices can be statically defined, or can be bound to data storage such as a database, a bean or a combination of both. The entire component is usually bound to data storage. When the page with the Combo Box is submitted, the selected item is stored in the specified location (for example, a column in the database or a property of the bean).

 

Component at design time

Drag and drop a

Combo Box component onto the page:

The

Combo Box component looks like this on the page:

 

Component at runtime

The

Combo Box component looks like this on the page during runtime:

 

Properties and All Attributes views

The Properties view for a component shows the most common set of attributes you can set on a component, and, depending on the component, you might also see options for adding controls, actions, or other components. To open the Properties view, click

Window | Show View | Properties.

These common attributes for the Combo Box component display on the h:selectOneMenu and Accessibility tabs in the Properties view. See the All Combo Box attributes table for a complete list of attributes. Additional configuration options to add item choices are on the h:selectOneMenu tab:

Configuration option	Description
Add a choice for each item in the combo box drop-down	Allows you to specify the names, values and order of items in the drop-down menu of the component.

Invalid values for selectOne components

Note:

The JSF lifecycle does not validate values when a page is initially rendered, as per the JSF standard. For example:

<h:inputText id="text2" styleClass="inputText" value="#{pc_Sa_RATLC00298618.myBean.myBigDecimal04}">
	<hx:convertNumber/>
	<f:validateDoubleRange minimum="10.0" maximum="99.0">
	</f:validateDoubleRange>
</h:inputText>

If the value initially resolves to something that is not in the specified range, the JSF tools will not mark an error (in an <h:message> tag). It is assumed that an invalid value is deliberately being used so that a user can correct it or to display an input message.

When the tag with an invalid value is a selectOne component, such as a combo box, a list box or a radio button group, an initial value is not set on the HTML tag (no option is selected) when the page is rendered. This is because an option that matches the invalid value cannot be located.

The browser will display nothing selected in the list box or radio button group since it is assumed that you are trying to force a user to choose a value. When the page is submitted, a value is not submitted (no selection) if non-valid choice has been made. If the field is marked as

"required", an error will be generated.

In the case of a combo box, the same thing is done, but the browser behavior differs. If a combo box has an invalid selection, the browser makes the first value the selection. As a result, when the page is submitted, a valid value is always submitted.

The All Attributes view shows a table of all the attributes you can set on a component, which includes those attributes you can access from the Properties view. To switch to the All Attributes view, click the

All Attributes icon in the upper right corner of the Properties view.

Table 1. All Combo Box attributes

Attribute name	Represented in Properties view by	Description
accesskey	Accessibility>Access Key	Specifies a single keyboard key as an access key. Pressing the specified access key at runtime gives focus to this component. Pressing ALT plus the specified access key at runtime gives focus to this component (or executes the component if it is a kind of button).
binding	Not represented	An expression that binds the component's instance (usually a user interface component) to a bean property (usually in the backing file).
converter	Not represented	Specifies the data type to which the value is converted. The JavaServer Faces implementation provides a set of Converter implementations that you can use to convert your component data to a type not supported by its renderer.
dir	Not represented	Specifies the component's direction when rendered at runtime. The values can be either: ltr - left to right rtl - right to left If the direction is not specified, a direction appropriate to the encoding of the component is used.
disabled	Not represented	If disabled is set to true, the component is displayed at runtime but is not functional. If left blank, the default value is false.
id	ID	Assigns a name to a component. Should be a unique name within a JSP.
immediate	Not represented	If true, skip straight to render phase of life cycle.
lang	Not represented	The language of the component's value(s) and text content. If omitted, the language is inherited from the containing tags (notably the view. Specified as an ISO-standard language abbreviation code. For example, "en" for English, "en-US" for American English, "fr" for French, "de" for German. Note: This does not "translate" the text in the component, rather, it identifies the language of the component so that operations such as searching, sorting, collating and the like are done correctly.
readonly	Not represented	Specifies that the value of the component cannot be changed from its initial value.
rendered	Not represented	Can be set to true or false: false - Component will not be rendered to the browser at runtime. true - Component will get rendered. This is the default value.
required	Not represented	The component must be specified. Check this to require the user to enter a value.
styleClass	Style: Classes	Space-separated list of CSS style classes to be applied when this element is rendered. This value must be passed through as the class attribute on generated markup. Defines the classes (such as style sheets) of the selected component. This may be done manually, or by clicking the button and selecting the desired Classes from within the window.
style	Style: Props	Specifies CSS style information for the component (for example, style="font-size : 8pt ; color : red"). Defines the properties (such as font and color) of the selected component. This may be done manually, or by clicking the button and selecting the desired properties from within the window.
tabindex	Accessibility>Tab order index	Specifies the position of the component in the tabbing order in the JSP. This value must be a number between 0 and 32767.
title	Accessibility>Title	Specifies the title text, shown in browser as a tooltip at runtime. Used by a browser as the alternative text of a component if the alternative text is not specified.
validator	Not represented	A method (represented by a MethodBinding expression) that accepts FacesContext, UIComponent, and Object parameters. It is called during the validation process to ensure that value of the component is correct.
valueChangeListener	Not represented	Method to be notified when value of component has changed.

 

Related tasks

Adding selection lists to a Faces JSP file

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