The HTML Tag Library Tags (Continued)


The HTML Tag Library Tags

The following table lists each of the tags in the HTML Tag Library and a short description of each tag's purpose.

Tag

Description

base

Generates an HTML <base> tag with its href attribute set to the absolute URL of the enclosing JSP.

button

Generates an HTML <input type="button"> tag.

cancel

Generates an HTML <input type="submit"> tag that, when executed, causes Struts' Cancel feature to be triggered.

checkbox

Generates an HTML <input type="checkbox"> tag populated with data from a specified object.

errors

Displays a set of error messages stored as an org.apache.struts.action. ActionErrors object, a String, or a String array in any scope.

file

Generates an HTML <input type="file"> tag populated with data from a specified object.

form

Generates an HTML <form> tag tied to an Action object and its corresponding Form Bean from the struts-config.xml file.

frame

Generates an HTML <frame> tag.

hidden

Generates an HTML <input type="hidden"> tag populated with data from a specified object.

html

Generates an HTML <html> tag with language attributes set to the current user's locale.

image

Generates an HTML <input type="image"> tag.

img

Generates an HTML <img> tag.

javascript

Generates client-side JavaScript validation code for validations defined in the Validator framework's validation.xml file.

link

Generates an HTML hyperlink <a> tag whose URL is composed by specifying a base URL and optionally specifying an anchor and/or query string parameters to add to the URL.

messages

Displays a set of messages stored as an org.apache.struts.action. ActionErrors object, an org.apache.struts.action.ActionMessages object, a String, or a String array in any scope.

multibox

Generates an HTML <input type="checkbox"> tag whose checked status is based on whether a specified value matches one of the values in a specified array of values.

option

Generates an HTML <option> tag.

options

Generates a set of HTML <option> tags for each element in a collection.

optionsCollection

Generates a set of HTML <option> tags for each element in a collection.

password

Generates an HTML <input type="password"> tag populated with data from a specified object.

radio

Generates an HTML <input type="radio"> tag populated with data from a specified object.

reset

Generates an HTML <input type="reset"> tag.

rewrite

Generates a URL by specifying a base URL and optionally specifying an anchor and/or query string parameters to add to the URL.

select

Generates an HTML <select> tag.

submit

Generates an HTML <input type="submit"> tag.

text

Generates an HTML <input type="text"> tag populated with data from a specified object.

textarea

Generates an HTML <textarea> tag populated with data from a specified object.

xhtml

Instructs the rest of the tags in the HTML Tag Library to generate their output as XHTML instead of HTML.

The remainder of this chapter discusses each tag in detail, including a complete description of the tag, a table listing each of the tag's attributes, and a usage example for the tag. In the tables that describe each tag's attributes, pay special attention to the Required and Accepts JSP Expression columns.

The Required column simply denotes whether the given attribute is required when using the tag. In addition to the required column denoting whether an attribute is required, the rows for required attributes are highlighted in gray so that you can determine at a glance which attributes are required.

If an attribute is required and you do not specify it when using the tag, the tag will throw a javax.servlet.jsp.JspException at run time. Note that you can declare an error page in your JSP with a page directive to capture any JspExceptions that might be thrown, as shown here:

<%@ page errorPage="error.jsp" %>

If an exception occurs, the page specified by the errorPage attribute will be internally redirected to display an error page.

The Accepts JSP Expression column denotes whether the given attribute's value can be specified with a JSP expression. If a JSP expression is used to specify an attribute value, the expression must comprise the complete value, quote (") to quote ("), as shown here. Correct:

<html:checkbox property="<%=prop%>">

Incorrect:

<html:checkbox property="<%=result%>-checked"> 

Notice in the incorrect example that "-checked" is used as part of the value for the property attribute following the expression. This is invalid because there are extra characters between the end of the expression and the ending quote.

A corrected version of the incorrect example follows:

<html:checkbox property="<%=result + "-checked"%>"/>

The concatenation of "-checked" is now part of the expression, and the expression comprises the complete value for the attribute.

One other point: Several of the tags have a set of tag attributes in common, such as onclick, onmousedown, and onkeypress. Rather than repeat the description for these common attributes numerous times, they are described once, at the end of this chapter, in the section"Common Tag Attributes." The Description column in each tag's table of attributes refers you to the section "Common Tag Attributes" for any of the common tag attributes that the tag has in its set of tag attributes.

The base Tag

The base tag is used to generate an HTML <base> tag with its href attribute set to the absolute URL of the enclosing JSP. Note that this tag must be nested inside of an HTML <head> tag.

Attributes

Attribute

Description

Accepts JSP Expression

Required

ref

Specifies what the base URL will be based on. This attribute accepts two values: page (default) for basing the URL on the location of the enclosing JSP or site for basing the URL on the application's context path.

Added in Struts 1.3.

Yes

No

server

Specifies the server name to use when generating the corresponding HTML tag's href attribute.

Yes

No

target

Same as the corresponding HTML tag's attribute with the same name.

Specifies the frame or window target in which links will be opened.

Yes

No

Example Usage

The following snippet shows the basic usage of the base tag:

<html:html> <head>   <title></title>   <html:base/> </head>

Remember that this tag must be enclosed by opening and closing HTML <head> tags.

The button Tag

The button tag is used to generate an HTML <input type="button"> tag. Note that this tag must be nested inside of this library's form tag.

Attributes

Attribute

Description

Accepts JSP Expression

Required

accesskey

See the section "Common Tag Attributes" at the end of this chapter.

Yes

No

alt

See "Common Tag Attributes."

Yes

No

altKey

See "Common Tag Attributes."

Yes

No

bundle

See "Common Tag Attributes."

Yes

No

disabled

See "Common Tag Attributes."

Yes

No

indexed

See "Common Tag Attributes."

Yes

No

onblur

See "Common Tag Attributes."

Yes

No

onchange

See "Common Tag Attributes."

Yes

No

onclick

See "Common Tag Attributes."

Yes

No

ondblclick

See "Common Tag Attributes."

Yes

No

onfocus

See "Common Tag Attributes."

Yes

No

onkeydown

See "Common Tag Attributes."

Yes

No

onkeypress

See "Common Tag Attributes."

Yes

No

onkeyup

See "Common Tag Attributes."

Yes

No

onmousedown

See "Common Tag Attributes."

Yes

No

onmousemove

See "Common Tag Attributes."

Yes

No

onmouseout

See "Common Tag Attributes."

Yes

No

onmouseover

See "Common Tag Attributes."

Yes

No

onmouseup

See "Common Tag Attributes."

Yes

No

property

Same as the corresponding HTML tag's name attribute.

Specifies the name that will be associated with this control.

Yes

Yes

style

See "Common Tag Attributes."

Yes

No

styleClass

See "Common Tag Attributes."

Yes

No

styleId

See "Common Tag Attributes."

Yes

No

tabindex

See "Common Tag Attributes."

Yes

No

title

See "Common Tag Attributes."

Yes

No

titleKey

See "Common Tag Attributes."

Yes

No

value

Specifies a constant value that this control will be populated with. This value will be used for the button's label. If not specified, this tag will attempt to use its body content as the value for the button's label.

Yes

No

Example Usage

The following snippet illustrates the basic usage of the button tag:

<html:button property="direction" value="Next Page"/>

The value specified with the value attribute will be used for the button's label. Alternatively, you can specify the button's label value by nesting a string between opening and closing button tags, as shown here:

<html:button>Next Page</html:button>

The cancel Tag

Struts has a built-in Cancel feature that will cause it to bypass calling a Form Bean's validate( ) method if a request parameter named "org.apache.struts.taglib.html.CANCEL" is present in an incoming request. Additionally, Action objects can call an isCancelled( ) method to determine whether a request was canceled. Note that as of Struts 1.3 an org. apache.struts.action.InvalidCancelException will be thrown at run time if the cancel button generated by this tag is clicked and the form's associated action mapping in the Struts configuration file does not have its cancellable attribute set to true.

The cancel tag is used to generate an HTML <input type="submit"> tag with its name attribute set to "org.apache.struts.taglib.html.CANCEL" so that, when executed, Struts' Cancel feature will be triggered. Note that this tag must be nested inside of the form tag.

Attributes

Attribute

Description

Accepts JSP Expression

Required

accesskey

See the section "Common Tag Attributes" at the end of this chapter.

Yes

No

alt

See "Common Tag Attributes."

Yes

No

altKey

See "Common Tag Attributes."

Yes

No

bundle

See "Common Tag Attributes."

Yes

No

disabled

See "Common Tag Attributes."

Yes

No

onblur

See "Common Tag Attributes."

Yes

No

onchange

See "Common Tag Attributes."

Yes

No

onclick

See "Common Tag Attributes."

Yes

No

ondblclick

See "Common Tag Attributes."

Yes

No

onfocus

See "Common Tag Attributes."

Yes

No

onkeydown

See "Common Tag Attributes."

Yes

No

onkeypress

See "Common Tag Attributes."

Yes

No

onkeyup

See "Common Tag Attributes."

Yes

No

onmousedown

See "Common Tag Attributes."

Yes

No

onmousemove

See "Common Tag Attributes."

Yes

No

onmouseout

See "Common Tag Attributes."

Yes

No

onmouseover

See "Common Tag Attributes."

Yes

No

onmouseup

See "Common Tag Attributes."

Yes

No

property

Same as the corresponding HTML tag's name attribute.

Specifies the name that will be associated with this control.

See the Caution about this attribute following this table.

Yes

No

style

See "Common Tag Attributes."

Yes

No

styleClass

See "Common Tag Attributes."

Yes

No

styleId

See "Common Tag Attributes."

Yes

No

tabindex

See "Common Tag Attributes."

Yes

No

title

See "Common Tag Attributes."

Yes

No

titleKey

See "Common Tag Attributes."

Yes

No

value

Specifies a constant value that this control will be populated with. This value will be used for the button's label. If not specified, this tag will attempt to use its body content as the value for the button's label.

Yes

No

Caution 

If you set the property attribute to a value other than its default, Struts' Cancel feature will not be triggered.

Example Usage

The following snippet illustrates the basic usage of the cancel tag:

<html:cancel value="Cancel Update"/>

The value specified with the value attribute will be used for the button's label. Alternatively, you can specify the button's label value by nesting a string between opening and closing cancel tags, as shown here:

<html:cancel>Cancel Update</html:cancel> 

The checkbox Tag

The checkbox tag is used to generate an HTML <input type="checkbox"> tag populated with data from a specified object. Note that this tag must be nested inside of this library's form tag. Additionally, the underlying Form Bean field associated with this control must be of primitive type boolean or of type Boolean and the Form Bean's reset( ) method must include a statement that resets the field to false.

Attributes

Attribute

Description

Accepts JSP Expression

Required

accesskey

See the section "Common Tag Attributes"

Yes

No

 

at the end of this chapter.

  

alt

See "Common Tag Attributes."

Yes

No

altKey

See "Common Tag Attributes."

Yes

No

bundle

See "Common Tag Attributes."

Yes

No

disabled

See "Common Tag Attributes."

Yes

No

errorKey

Specifies the name of the org.apache. struts.util.MessageResources object that contains the messages to be rendered. Defaults to the value stored in the org. apache.struts.Globals.ERROR_KEY constant.

Yes

No

errorStyle

Specifies the CSS style to apply to this control if an error exists for it.

Yes

No

errorStyleClass

Specifies the CSS class to apply to this control if an error exists for it.

Yes

No

errorStyleId

Specifies the CSS ID to apply to this control if an error exists for it.

Yes

No

indexed

See "Common Tag Attributes."

Yes

No

name

Specifies the name of an object (in any scope) whose field, specified by the property attribute, will be used to populate this control with data.

Yes

No

onblur

See "Common Tag Attributes."

Yes

No

onchange

See "Common Tag Attributes."

Yes

No

onclick

See "Common Tag Attributes."

Yes

No

ondblclick

See "Common Tag Attributes."

Yes

No

onfocus

See "Common Tag Attributes."

Yes

No

onkeydown

See "Common Tag Attributes."

Yes

No

onkeypress

See "Common Tag Attributes."

Yes

No

onkeyup

See "Common Tag Attributes."

Yes

No

onmousedown

See "Common Tag Attributes."

Yes

No

onmousemove

See "Common Tag Attributes."

Yes

No

onmouseout

See "Common Tag Attributes."

Yes

No

onmouseover

See "Common Tag Attributes."

Yes

No

onmouseup

See "Common Tag Attributes."

Yes

No

property

Specifies the value to set the corresponding HTML tag's name attribute to. Additionally, this attribute is used to specify the field of the object specified by the name attribute whose getter method will be called to return an object whose value will be used to populate this control. If no object is specified with the name attribute, the Form Bean object associated with the enclosing form tag will be used to retrieve the property specified by this attribute.

Yes

Yes

style

See "Common Tag Attributes."

Yes

No

styleClass

See "Common Tag Attributes."

Yes

No

styleId

See "Common Tag Attributes."

Yes

No

tabindex

See "Common Tag Attributes."

Yes

No

title

See "Common Tag Attributes."

Yes

No

titleKey

See "Common Tag Attributes."

Yes

No

value

Specifies a constant value that the control will be populated with.

Yes

No

Example Usage

The following snippet illustrates the basic usage of the checkbox tag:

<html:form action="/register"> Subscribe to mailing list: <html:checkbox property="subscribe"/><br> <html:submit/> </html:form>

This tag will look up the Form Bean associated with the Action specified by the form tag's action attribute and then call the getter method for the field specified by this tag's property attribute. The field's value will then be used to populate the HTML control with data.

The errors Tag

The errors tag is used to display a set of error messages stored as an org.apache.struts. action.ActionErrors object, a String, or a String array in any scope. This tag will take the stored error messages and iterate over them, displaying them in succession. Additionally, this tag uses the values for the following table of keys from the application resource bundle file (e.g., MessageResources.properties) to format the messages.

Key

Purpose

errors.header

Text that will be output before the list of error messages.

errors.footer

Text that will be output after the list of error messages.

errors.prefix

Text that will be output before each error message.

errors.suffix

Text that will be output after each error message.

Attributes

Attribute

Description

Accepts JSP Expression

Required

bundle

Specifies the logical name of a resource bundle that will be used when looking up message keys. The referenced resource bundle must be defined in the application's Struts configuration file.

Yes

No

footer

Specifies text that will be output after the list of error messages. If not specified, defaults to text stored under the "errors.footer" key in your application's resource bundle.

Yes

No

header

Specifies text that will be output before the list of error messages. If not specified, defaults to text stored under the "errors.header" key in your application's resource bundle.

Yes

No

locale

Specifies the key for a java.util.Locale instance stored as a session attribute that will be used when looking up error keys.

Yes

No

name

Specifies the key (in any scope) under which the errors to be displayed are stored. If not specified, the default org.apache.struts. Globals.ERROR_KEY key will be used.

Yes

No

prefix

Specifies text that will be output before each error message. If not specified, defaults to text stored under the "errors.prefix" key in your application's resource bundle.

Yes

No

property

Specifies the field for which errors will be displayed. If not specified, all errors will be displayed.

Yes

No

suffix

Specifies text that will be output after each error message. If not specified, defaults to text stored under the "errors.suffix" key in your application's resource bundle.

Yes

No

Example Usage

The following snippet illustrates the basic usage of the errors tag:

<html:errors/>

This example will display all the errors currently stored. If you want to limit the errors that are displayed to a specific property, you can specify that property when using the errors tag, as shown here:

<html:errors property="username"/>

In this case, only the errors associated with the property specified by the property attribute will be displayed.

The file Tag

The file tag is used to generate an HTML <input type="file"> tag populated with data from a specified object. Note that this tag must be nested inside of the form tag. Additionally, the enclosing form tag must specify its HTTP method as being POST and its encoding type as being multipart/form-data, as shown here:

<html:form method="POST" enctype="multipart/form-data"> … </html:form> 

Attributes

Attribute

Description

Accepts JSP Expression

Required

accept

Same as the corresponding HTML tag's attribute with the same name. Specifies a comma-delimited list of content types that the server you submit the enclosing form to knows how to process. Browsers can use this list to limit the set of files made available for selection.

Yes

No

accesskey

See the section "Common Tag Attributes" at the end of this chapter.

Yes

No

alt

See "Common Tag Attributes."

Yes

No

altKey

See "Common Tag Attributes."

Yes

No

bundle

See "Common Tag Attributes."

Yes

No

disabled

See "Common Tag Attributes."

Yes

No

errorKey

Specifies the name of the org.apache. struts.util.MessageResources object that contains the messages to be rendered. Defaults to the value stored in the org. apache.struts.Globals.ERROR_KEY constant.

Yes

No

errorStyle

Specifies the CSS style to apply to this control if an error exists for it.

Yes

No

errorStyleClass

Specifies the CSS class to apply to this control if an error exists for it.

Yes

No

errorStyleId

Specifies the CSS ID to apply to this control if an error exists for it.

Yes

No

indexed

See "Common Tag Attributes."

Yes

No

maxlength

Same as the corresponding HTML tag's attribute with the same name. Specifies the maximum number of characters that this control will accept.

Yes

No

name

Specifies the name of an object (in any scope) whose field, specified by the property attribute, will be used to populate this control with data.

Yes

No

onblur

See "Common Tag Attributes."

Yes

No

onchange

See "Common Tag Attributes."

Yes

No

onclick

See "Common Tag Attributes."

Yes

No

ondblclick

See "Common Tag Attributes."

Yes

No

onfocus

See "Common Tag Attributes."

Yes

No

onkeydown

See "Common Tag Attributes."

Yes

No

onkeypress

See "Common Tag Attributes."

Yes

No

onkeyup

See "Common Tag Attributes."

Yes

No

onmousedown

See "Common Tag Attributes."

Yes

No

onmousemove

See "Common Tag Attributes."

Yes

No

onmouseout

See "Common Tag Attributes."

Yes

No

onmouseover

See "Common Tag Attributes."

Yes

No

onmouseup

See "Common Tag Attributes."

Yes

No

property

Specifies the value to which the corresponding HTML tag's name attribute is set. Additionally, this attribute is used to specify the field of the object specified by the name attribute whose getter method will be called to return an object whose value will be used to populate this control. If no object is specified with the name attribute, the Form Bean object associated with the enclosing form tag will be used to retrieve the property specified by this attribute.

Yes

Yes

size

Same as the corresponding HTML tag's attribute with the same name.

Specifies the number of characters that will be visible in the control.

Yes

No

style

See "Common Tag Attributes."

Yes

No

styleClass

See "Common Tag Attributes."

Yes

No

styleId

See "Common Tag Attributes."

Yes

No

tabindex

See "Common Tag Attributes."

Yes

No

title

See "Common Tag Attributes."

Yes

No

titleKey

See "Common Tag Attributes."

Yes

No

value

Specifies a constant value that is used to populate the control.

Yes

No

Example Usage

The following snippet illustrates the basic usage of the file tag:

<html:form method="POST"           enctype="multipart/form-data"            action="/attachFile"> Upload File: <html:file property="uploadFile"/><br> <html:submit/> </html:form>

This tag will look up the Form Bean associated with the Action specified by the form tag's action attribute and then call the getter method for the field specified by this tag's property attribute. The field's value will then be used to populate the HTML control with data.

The form Tag

The form tag is used to generate an HTML <form> tag tied to an Action and its corresponding Form Bean from the Struts configuration file (e.g., struts-config.xml). The Action's Form Bean will be used by other tags from this library to populate them with data when they are nested inside this tag.

Attributes

Attribute

Description

Accepts JSP Expression

Required

acceptCharset

Specifies the list of character encodings that the server should accept for field input data.

Yes

No

action

Specifies the logical name of an Action, defined in the Struts configuration file, whose path will be used to define the corresponding HTML tag's attribute with the same name. If not specified, the original URI for the request will be used.

Yes

No

disabled

See the section "Common Tag Attributes" at the end of this chapter.

Yes

No

enctype

Same as the corresponding HTML tag's attribute with the same name.

Specifies the encoding to be used when submitting this form if the POST method is used. This must be set to "multipart/form-data" if you are using the file tag to upload files.

Yes

No

focus

Specifies the name of a field inside this form that initial focus will be assigned to using JavaScript.

Yes

No

focusIndex

Specifies an index to be used if the field specified with the focus attribute is a field array such as a radio button group.

Yes

No

method

Same as the corresponding HTML tag's attribute with the same name.

Specifies the HTTP method that will be used when submitting this form (e.g., GET or POST).

Yes

No

onreset

Same as the corresponding HTML tag's attribute with the same name.

Specifies the JavaScript code to execute when this form is reset.

Yes

No

onsubmit

Same as the corresponding HTML tag's attribute with the same name.

Specifies the JavaScript code to execute when this form is submitted.

Yes

No

readonly

Same as the corresponding HTML tag's attribute with the same name.

Accepts true or false to specify whether the form elements will be read-only, preventing them from being changed. Defaults to false.

Yes

No

scriptLanguage

Accepts true or false to specify whether the language attribute of the <focus> tag generated by this tag's focus attribute should be omitted. Note that the generated <focus> tag's language attribute is omitted regardless when the tags in this library are in XHTML mode.

Defaults to true.

Yes

No

style

See "Common Tag Attributes."

Yes

No

styleClass

See "Common Tag Attributes."

Yes

No

styleId

See "Common Tag Attributes."

Yes

No

target

Same as the corresponding HTML tag's attribute with the same name.

Specifies the frame or window target in which this form will be submitted.

Yes

No

Example Usage

The following snippet illustrates the basic usage of the form tag:

 <html:form action="/logon"> UserName: <html:text property="username"/><br> Password: <html:password property="password"/><br> <html:submit/> </html:form> 

The Form Bean associated with the Action specified by the action attribute will be used for populating the nested HTML controls inside the opening and closing form tags.

If you want to use a postback form, use the form tag as shown here:

 <html:form> UserName: <html:text property="username"/><br> Password: <html:password property="password"/><br> <html:submit/> </html:form> 

In this scenario, the URI of the original request is used to populate the rendered HTML tag's action attribute.

The frame Tag

The frame tag is used to generate an HTML <frame> tag. The frame's URL is composed by specifying a base URL and optionally specifying an anchor and/or query string parameters to add to the URL.

There are four ways to specify the base URL:

  • You can use the action attribute to specify the name of an Action from the Struts configuration file whose URL will be used.

  • You can use the forward attribute to specify the name of a forward from the Struts configuration file whose URL will be used.

  • You can use the href attribute to specify an absolute URL, including protocol (e.g., http://www.yahoo.com/).

  • You can use the page attribute to specify an application-relative URL.

In addition to specifying the base URL, you have two options for specifying query string parameters to add to the base URL:

  • You can use the paramId attribute in conjunction with the paramName attribute, and optionally the paramProperty attribute, to specify a single parameter.

  • You can use the name attribute, either alone or in tandem with the property attribute, to specify a java.util.Map object that will be used to add several parameters.

Attributes

Attribute

Description

Accepts JSP Expression

Required

action

Specifies the name of an Action, from the Action Mappings section of the Struts configuration file, which contains the URL for this frame.

Yes

No

anchor

Specifies the anchor (e.g., "#bottom") to be added to the URL for this frame. This value must be specified without the leading hash (#) character.

Yes

No

bundle

See the section "Common Tag Attributes" at the end of this chapter.

Yes

No

forward

Specifies the name of a forward, from the Global Forwards Configuration section of the Struts configuration file, that contains the URL for this frame.

Yes

No

frameborder

Same as the corresponding HTML tag's attribute with the same name.

Specifies the border size for this frame (0 for no border).

Yes

No

frameName

Same as the corresponding HTML tag's name attribute.

Specifies the logical name to give the frame.

Yes

No

href

Specifies the absolute URL, including protocol (e.g., http://www.yahoo.com), for this frame.

Yes

No

longdesc

Same as the corresponding HTML tag's attribute with the same name.

Specifies the URL for a long description of the frame that supplements the short description provided by the title attribute.

Yes

No

marginheight

Same as the corresponding HTML tag's attribute with the same name.

Specifies the number of pixels that will be placed between this frame's contents and its top and bottom margins.

Yes

No

marginwidth

Same as the corresponding HTML tag's attribute with the same name.

Specifies the number of pixels that will be placed between this frame's contents and its left and right margins.

Yes

No

module

Specifies the name of a module that contains the action mapping for the Action specified with the action attribute.

Yes

No

name

Specifies the name of the java.util.Map object whose elements are added as query string parameters to the URL for this frame. If the property attribute is also specified, one of the fields of the object defined by this attribute will have its getter method called to return the java.util.Map object whose elements are added as query string parameters to the URL for this frame.

Yes

No

noresize

Same as the corresponding HTML tag's attribute with the same name.

Accepts true or false to specify whether this frame will not be resizable.

Defaults to false.

Yes

No

page

Specifies the application-relative URL (starts with a leading slash, /) for this frame.

Yes

No

paramId

Specifies the name of a single parameter to add to the URL for this frame.

Yes

No

paramName

Specifies the name of an object whose value will be used as the value for the parameter specified with the paramId attribute. If the property attribute is also specified, one of the fields of the object defined by this attribute will have its getter method called to return an object whose value will be used as the value for the parameter specified with the paramId attribute.

Yes

No

paramProperty

Specifies the field of the object specified by the name attribute whose getter method will be called to return an object whose value will be used as the value for the parameter specified with the paramId attribute.

Yes

No

paramScope

Specifies the scope (application, page, request, or session) to look in for the object specified by the paramName attribute. If not specified, each scope will be searched, in this order: page, request, session, and then application.

Yes

No

property

Specifies the field of the object specified by the name attribute whose getter method will be called to return the java.util.Map object whose elements are added as query string parameters to the URL for this frame.

Yes

No

scope

Specifies the scope (application, page, request, or session) to look in for the object specified by the name attribute. If not specified, each scope will be searched, in this order: page, request, session, and then application.

Yes

No

scrolling

Same as the corresponding HTML tag's attribute with the same name.

Specifies whether this frame is scrollable. Specify yes to have scroll bars unconditionally, no to never have scroll bars, or auto to have scroll bars automatically based on how much content is in the frame.

Yes

No

style

See "Common Tag Attributes."

Yes

No

styleClass

See "Common Tag Attributes."

Yes

No

styleId

See "Common Tag Attributes."

Yes

No

title

See "Common Tag Attributes."

Yes

No

titleKey

See "Common Tag Attributes."

Yes

No

transaction

Accepts true or false to specify whether the current transaction token is included in the URL for this frame.

Defaults to false.

Yes

No

Example Usage

There are a few different ways to use the frame tag. The first way, shown here, uses the href attribute to specify an absolute URL for the frame:

<html:frame href="http://www.yahoo.com/"/>

The following example adds to the first example by specifying a single query string parameter to add to the base URL specified by the href attribute:

<html:frame href="http://www.yahoo.com/"          param        paramName="queryObj"/> 

This example takes the base URL specified by the href attribute and appends the query string parameter specified by the paramId and paramName attributes and composes a URL for the frame.

Another way to use the frame tag is shown here:

<html:frame page="/search.jsp" name="params"/>

This example uses the page attribute to specify an application-relative base URL and uses the name attribute to specify a java.util.Map object whose entries are added to the URL as query string parameters.

The hidden Tag

The hidden tag is used to generate an HTML <input type="hidden"> tag populated with data from a specified object. Note that this tag must be nested inside of the form tag.

Attributes

Attribute

Description

Accepts JSP Expression

Required

accesskey

See the section "Common Tag Attributes" at the end of this chapter.

Yes

No

alt

See "Common Tag Attributes."

Yes

No

altKey

See "Common Tag Attributes."

Yes

No

bundle

See "Common Tag Attributes."

Yes

No

disabled

See "Common Tag Attributes."

Yes

No

indexed

See "Common Tag Attributes."

Yes

No

name

Specifies the name of an object (in any scope) whose field, specified by the property attribute, will be used to populate this control with data.

Yes

No

onblur

See "Common Tag Attributes."

Yes

No

onchange

See "Common Tag Attributes."

Yes

No

onclick

See "Common Tag Attributes."

Yes

No

ondblclick

See "Common Tag Attributes."

Yes

No

onfocus

See "Common Tag Attributes."

Yes

No

onkeydown

See "Common Tag Attributes."

Yes

No

onkeypress

See "Common Tag Attributes."

Yes

No

onkeyup

See "Common Tag Attributes."

Yes

No

onmousedown

See "Common Tag Attributes."

Yes

No

onmousemove

See "Common Tag Attributes."

Yes

No

onmouseout

See "Common Tag Attributes."

Yes

No

onmouseover

See "Common Tag Attributes."

Yes

No

onmouseup

See "Common Tag Attributes."

Yes

No

property

Specifies the value to which the corresponding HTML tag's name attribute is set. Additionally, this attribute is used to specify the field of the object specified by the name attribute whose getter method will be called to return an object whose value will be used to populate this control. If no object is specified with the name attribute, the Form Bean object associated with the enclosing form tag will be used to retrieve the property specified by this attribute.

Yes

Yes

style

See "Common Tag Attributes."

Yes

No

styleClass

See "Common Tag Attributes."

Yes

No

styleId

See "Common Tag Attributes."

Yes

No

title

See "Common Tag Attributes."

Yes

No

titleKey

See "Common Tag Attributes."

Yes

No

value

Specifies a constant value that this control will be populated with.

Yes

No

write

Accepts true or false to specify whether this control's value will also be written out to the page so that it is visible.

Defaults to false.

Yes

No

Example Usage

The following snippet illustrates the basic usage of the hidden tag:

<html:form action="/search"> <html:hidden property="lastId"/> <html:submit/> </html:form>

This tag will look up the Form Bean associated with the Action specified by the form tag's action attribute and then call the getter method for the field specified by this tag's property attribute. The field's value will then be used to populate the HTML control with data.

The html Tag

The html tag is used to generate an HTML <html> tag with language attributes set to the current user's locale. Additionally, you can use this tag to instruct the rest of the tags in the HTML Tag Library to generate their output as XHTML instead of HTML. More information on XHTML can be found at http://www.xhtml.org/.

Attributes

Attribute

Description

Accepts JSP Expression

Required

lang

Accepts true or false to specify whether an attribute of the same name will be rendered on the generated <html> tag. If set to true, the attribute will be set to the language from the locale currently stored in the user's session. If there is not a locale stored in the session, the language will be set to that specified by the current request's "AcceptLanguage" HTTP header. Finally, if there is not an "AcceptLanguage" header value, the language will be set to server's default.

Defaults to false.

Yes

No

xhtml

Accepts true or false to specify whether the rest of the tags in the HTML Tag Library will generate their output as XHTML instead of HTML.

Defaults to false.

Yes

No

Example Usage

The following snippet shows the basic usage of the html tag:

<html:html/>

If you want the HTML Tag Library's tags to generate XHTML instead of HTML, use the html tag as shown here:

<html:html xhtml="true"/>

The image Tag

The image tag is used to generate an HTML <input type="image"> tag. Note that this tag must be nested inside of a form tag.

There are two ways you can use the image tag, as listed here and shown later, in the section "Example Usage":

  • You can use the page or pageKey attribute to specify a module-relative URL that will be used as the generated HTML tag's src attribute.

  • You can use the src or srcKey attribute to specify a URL that will be used as the generated HTML tag's src attribute.

Attributes

Attribute

Description

Accepts JSP Expression

Required

accesskey

See the section "Common Tag Attributes" at the end of this chapter.

Yes

No

align

Same as the corresponding HTML tag's attribute with the same name.

Specifies how the image will be aligned (i.e., left, right, top, bottom, and so on).

Yes

No

alt

See "Common Tag Attributes."

Yes

No

altKey

See "Common Tag Attributes."

Yes

No

border

Same as the corresponding HTML tag's attribute with the same name.

Specifies the width of the border surrounding the image.

Yes

No

bundle

See "Common Tag Attributes."

Yes

No

disabled

See "Common Tag Attributes."

Yes

No

indexed

See "Common Tag Attributes."

Yes

No

locale

Specifies the key for a java.util.Locale instance stored as a session attribute that will be used when looking up message keys specified by other attributes of this tag (i.e., pageKey and srcKey).

Yes

No

onblur

See "Common Tag Attributes."

Yes

No

onchange

See "Common Tag Attributes."

Yes

No

onclick

See "Common Tag Attributes."

Yes

No

ondblclick

See "Common Tag Attributes."

Yes

No

onfocus

See "Common Tag Attributes."

Yes

No

onkeydown

See "Common Tag Attributes."

Yes

No

onkeypress

See "Common Tag Attributes."

Yes

No

onkeyup

See "Common Tag Attributes."

Yes

No

onmousedown

See "Common Tag Attributes."

Yes

No

onmousemove

See "Common Tag Attributes."

Yes

No

onmouseout

See "Common Tag Attributes."

Yes

No

onmouseover

See "Common Tag Attributes."

Yes

No

onmouseup

See "Common Tag Attributes."

Yes

No

page

Specifies a module-relative URL for this button's image.

Yes

No

pageKey

Specifies a key from the application resource bundle whose value will be used to set the corresponding HTML tag's src attribute with a module-relative URL.

Yes

No

property

Same as the corresponding HTML tag's name attribute.

Specifies the name that will be associated with this control.

Yes

No

src

Same as the corresponding HTML tag's attribute with the same name.

Specifies the source URL for this button's image.

Yes

No

srcKey

Specifies a key from the application resource bundle whose value will be used to set the corresponding HTML tag's src attribute.

Yes

No

style

See "Common Tag Attributes."

Yes

No

styleClass

See "Common Tag Attributes."

Yes

No

styleId

See "Common Tag Attributes."

Yes

No

tabindex

See "Common Tag Attributes."

Yes

No

title

See "Common Tag Attributes."

Yes

No

titleKey

See "Common Tag Attributes."

Yes

No

value

Specifies a constant value that this control will be populated with. If not specified, this tag will attempt to use its body content as the value.

Yes

No

Example Usage

As mentioned, there are two ways you can use the image tag. The first way, shown here, uses the page attribute to specify a module-relative URL for the generated HTML tag's src attribute:

<html:image page="previous.gif"/>

The second way to use the image tag is shown here:

<html:image src="/books/1/249/1/html/2//images/next.gif"/>

This example uses the src attribute to specify a URL for the generated HTML tag's src attribute. The image tag will be used in this way for most applications; however, if you are taking advantage of Struts' module functionality, you will use the page or pageKey attribute.



Struts. The Complete Reference
Struts: The Complete Reference, 2nd Edition
ISBN: 0072263865
EAN: 2147483647
Year: 2004
Pages: 165
Authors: James Holmes

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