Struts Bean Tags |
This tag library contains tags useful in accessing beans and their
properties, as well as defining new beans (based on these accesses)
that are accessible to the remainder of the page via scripting variables
and page scope attributes. Convenient mechanisms to create new beans
based on the value of request cookies, headers, and parameters are also
provided.
Many of the tags in this tag library will throw a
JspException at runtime when they are utilized incorrectly
(such as when you specify an invalid combination of tag attributes). JSP
allows you to declare an "error page" in the <%@ page %>
directive. If you wish to process the actual exception that caused the
problem, it is passed to the error page as a request attribute under key
org.apache.struts.action.EXCEPTION .
If you are viewing this page from within the Struts Documentation
Application (or online at
http://jakarta.apache.org/struts), you can learn more about using
these tags in the
Bean Tags Developer's Guide.
| Tag Name | Description |
---|
cookie |
Define a scripting variable based on the value(s) of the specified
request cookie.
| define |
Define a scripting variable based on the value(s) of the specified
bean property.
| header |
Define a scripting variable based on the value(s) of the specified
request header.
| include |
Load the response from a dynamic application request and make it available
as a bean.
| message |
Render an internationalized message string to the response.
| page |
Expose a specified item from the page context as a bean.
| parameter |
Define a scripting variable based on the value(s) of the specified
request parameter.
| resource |
Load a web application resource and make it available as a bean.
| size |
Define a bean containing the number of elements in a Collection or Map.
| struts |
Expose a named Struts internal configuration object as a bean.
| write |
Render the value of the specified bean property to the current
JspWriter.
|
|
cookie -
Define a scripting variable based on the value(s) of the specified
request cookie.
|
Retrieve the value of the specified request cookie (as a single
value or multiple values, depending on the multiple attribute),
and define the result as a page scope attribute of type Cookie
(if multiple is not specified) or Cookie[]
(if multiple is specified).
If no cookie with the specified name can be located, and no default
value is specified, a request time exception will be thrown.
| Attribute Name | Description |
---|
id |
Specifies the name of the scripting variable (and associated page
scope attribute) that will be made available with the value of the
specified request cookie.
(REQUIRED)
| multiple |
If any arbitrary value for this attribute is specified, causes all
matching cookies to be accumulated and stored into a bean of type
Cookie[] . If not specified, the first value for the
specified cookie will be retrieved as a value of type
Cookie .
(RT EXPR)
| name |
Specifies the name of the request cookie whose value, or values,
is to be retrieved.
(REQUIRED)
(RT EXPR)
| value |
The default cookie value to return if no cookie with the
specified name was included in this request.
(RT EXPR)
|
|
Back to top define -
Define a scripting variable based on the value(s) of the specified
bean property.
|
Create a new attribute (in the scope specified by the
toScope property, if any), and a corresponding scripting
variable, both of which are named by the value of the id
attribute. The corresponding value to which this new attribute (and
scripting variable) is set are specified via use of exactly one of the
following approaches (trying to use more than one will result in a
JspException being thrown):
- Specify a
name attribute (plus optional
property and scope attributes) -
The created attribute and scripting variable will be of the type of the
retrieved JavaBean property, unless it is a Java primitive type,
in which case it will be wrapped in the appropriate wrapper class
(i.e. int is wrapped by java.lang.Integer).
- Specify a
value attribute - The created attribute and
scripting variable will be of type java.lang.String ,
set to the value of this attribute.
- Specify nested body content - The created attribute and scripting
variable will be of type
java.lang.String , set to
the value of the nested body content.
If a problem occurs while retrieving the specified bean property, a
request time exception will be thrown.
The <bean:define> tag differs from
<jsp:useBean> in several ways, including:
- Unconditionally creates (or replaces) a bean under the
specified identifier.
- Can create a bean with the value returned by a property getter
of a different bean (including properties referenced with a
nested and/or indexed property name).
- Can create a bean whose contents is a literal string (or the result
of a runtime expression) specified by the
value
attribute.
- Does not support nested content (such as
<jsp:setProperty> tags) that are only executed
if a bean was actually created.
USAGE NOTE - There is a restriction in the JSP 1.1
Specification that disallows using the same value for an id
attribute more than once in a single JSP page. Therefore, you will not
be able to use <bean:define> for the same bean
name more than once in a single page.
USAGE NOTE - You cannot use bean:define to instantiate
a DynaActionForm (type="org.apache.struts.action.DynaActionForm") with
the properties specified in the struts-config. The mechanics of creating
the dyna-properties is complex and cannot be handled by a no-argument
constructor. If you need to create an ActionForm this way, you must use
a conventional ActionForm.
See the Bean Developer's Guide section on
bean creation for more information about these differences, as well
as alternative approaches to introducing beans into a JSP page.
| Attribute Name | Description |
---|
id |
Specifies the name of the scripting variable (and associated page
scope attribute) that will be made available with the value of the
specified property.
(REQUIRED)
| name |
Specifies the attribute name of the bean whose property is accessed
to define a new page scope attribute (if property is also
specified) or the attribute name of the bean that is duplicated with
the new reference created by this tag (if property is not
also specified). This attribute is required unless you specify
a value attribute or nested body content.
(RT EXPR)
| property |
Specifies the name of the property to be accessed on the bean
specified by name . This value may be a simple, indexed,
or nested property reference expression. If not specified, the bean
identified by name is given a new reference identified by
id .
(RT EXPR)
| scope |
Specifies the variable scope searched to retrieve the bean specified
by name . If not specified, the default rules applied by
PageContext.findAttribute() are applied.
(RT EXPR)
| toScope |
Specifies the variable scope into which the newly defined bean will
be created. If not specified, the bean will be created in
page scope.
(RT EXPR)
| type |
Specifies the fully qualified class name of the value to be exposed
as the id attribute.
[
java.lang.String (if you specify a value
attribute) or java.lang.Object otherwise.
]
(RT EXPR)
| value |
The java.lang.String value to which the exposed bean
should be set. This attribute is required unless you specify the
name attribute or nested body content.
(RT EXPR)
|
|
Back to top header -
Define a scripting variable based on the value(s) of the specified
request header.
|
Retrieve the value of the specified request header (as a single
value or multiple values, depending on the multiple attribute),
and define the result as a page scope attribute of type String
(if multiple is not specified) or String[]
(if multiple is specified).
If no header with the specified name can be located, and no default
value is specified, a request time exception will be thrown.
| Attribute Name | Description |
---|
id |
Specifies the name of the scripting variable (and associated page
scope attribute) that will be made available with the value of the
specified request header.
(REQUIRED)
| multiple |
If any arbitrary value for this attribute is specified, causes a call
to HttpServletRequest.getHeaders() and a definition of the
result as a bean of type String[] . Otherwise,
HttpServletRequest.getHeader() will be called, and a
definition of the result as a bean of type String
will be performed.
(RT EXPR)
| name |
Specifies the name of the request header whose value, or values,
is to be retrieved.
(REQUIRED)
(RT EXPR)
| value |
The default header value to return if no header with the
specified name was included in this request.
(RT EXPR)
|
|
Back to top include -
Load the response from a dynamic application request and make it available
as a bean.
|
Perform an internal dispatch to the specified application component
(or external URL)
and make the response data from that request available as a bean of
type String . This tag has a function similar to that of
the standard <jsp:include> tag, except that the
response data is stored in a page scope attribute instead of being
written to the output stream. If the current request is part of a
session, the generated request for the include will also include the
session identifier (and thus be part of the same session).
The URL used to access the specified application component is
calculated based on which of the following attributes you specify
(you must specify exactly one of them):
- forward - Use the value of this attribute as the name
of a global
ActionForward to be looked up, and
use the application-relative or context-relative URI found there.
- href - Use the value of this attribute unchanged (since
this might link to a resource external to the application, the
session identifier is not included.
- page - Use the value of this attribute as an
application-relative URI to the desired resource.
| Attribute Name | Description |
---|
anchor |
Optional anchor tag ("#xxx") to be added to the generated
hyperlink. Specify this value without any
"#" character.
(RT EXPR)
| forward |
Logical name of a global ActionForward that contains
the actual content-relative URI of the resource to be included.
(RT EXPR)
| href |
Absolute URL (including the appropriate protocol prefix such as
"http:") of the resource to be included. Because this URL could be
external to the current web application, the session identifier will
not be included in the request.
(RT EXPR)
| id |
Specifies the name of the scripting variable (and associated page
scope attribute) that will be made available with the value of the
specified web application resource.
(REQUIRED)
| name |
Application-relative name (starting with a '/') of the web application
resource to be dispatched, and whose response data is to be made
available as a bean. DEPRECATED - Use the "page" attribute
instead.
(RT EXPR)
| page |
Application-relative URI (starting with a '/') of the web application
resource to be included.
(RT EXPR)
| transaction |
Set to true if you want the current
transaction control token included in the generated
URL for this include.
(RT EXPR)
|
|
Back to top message -
Render an internationalized message string to the response.
|
Retrieves an internationalized message for the specified locale,
using the specified message key, and write it to the output stream.
Up to five parametric replacements (such as "{0}") may be specified.
The message key may be specified directly, using the key
attribute, or indirectly, using the name and
property attributes to obtain it from a bean.
JSTL: The equivalent JSTL tag is <fmt:message>. For example,
<fmt:message key="my.msg.key">
<fmt:param value="replacement text"/>
</fmt:message>
| Attribute Name | Description |
---|
arg0 |
First parametric replacement value, if any.
(RT EXPR)
| arg1 |
Second parametric replacement value, if any.
(RT EXPR)
| arg2 |
Third parametric replacement value, if any.
(RT EXPR)
| arg3 |
Fourth parametric replacement value, if any.
(RT EXPR)
| arg4 |
Fifth parametric replacement value, if any.
(RT EXPR)
| bundle |
The name of the application scope bean under which the
MessageResources object containing our messages
is stored.
[Action.MESSAGES_KEY]
(RT EXPR)
| key |
The message key of the requested message, which must have
a corresponding value in the message resources. If not specified,
the key is obtained from the name and
property attributes.
(RT EXPR)
| locale |
The name of the session scope bean under which our currently
selected Locale object is stored.
[Action.LOCALE_KEY]
(RT EXPR)
| name |
Specifies the attribute name of the bean whose property is accessed
to retrieve the value specified by property (if
specified). If property is not specified, the value of
this bean itself will be used as the message resource key.
(RT EXPR)
| property |
Specifies the name of the property to be accessed on the bean
specified by name . This value may be a simple, indexed,
or nested property reference expression. If not specified, the value
of the bean identified by name will itself be used as the
message resource key.
(RT EXPR)
| scope |
Specifies the variable scope searched to retrieve the bean specified
by name . If not specified, the default rules applied by
PageContext.findAttribute() are applied.
(RT EXPR)
|
|
Back to top page -
Expose a specified item from the page context as a bean.
|
Retrieve the value of the specified item from the page context
for this page, and define it as a scripting variable, and a page scope
attribute accessible to the remainder of the current page.
If a problem occurs while retrieving the specified configuration
object, a request time exception will be thrown.
| Attribute Name | Description |
---|
id |
Specifies the name of the scripting variable (and associated
page scope attribute) that will be made available with the value of
the specified page context property.
(REQUIRED)
| property |
Name of the property from our page context to be retrieved and
exposed. Must be one of application , config ,
request , response , or session .
(REQUIRED)
(RT EXPR)
|
|
Back to top parameter -
Define a scripting variable based on the value(s) of the specified
request parameter.
|
Retrieve the value of the specified request parameter (as a single
value or multiple values, depending on the multiple attribute),
and define the result as a page scope attribute of type String
(if multiple is not specified) or String[]
(if multiple is specified).
If no request parameter with the specified name can be located, and
no default value is specified, a request time exception will be thrown.
| Attribute Name | Description |
---|
id |
Specifies the name of the scripting variable (and associated page
scope attribute) that will be made available with the value of the
specified request parameter.
(REQUIRED)
| multiple |
If any arbitrary value for this attribute is specified, causes a call
to ServletRequest.getParameterValues() and a definition of
the result as a bean of type String[] . Otherwise,
ServletRequest.getParameter() will be called, and a
definition of the result as a bean of type String
will be performed.
(RT EXPR)
| name |
Specifies the name of the request parameter whose value, or values,
is to be retrieved.
(REQUIRED)
(RT EXPR)
| value |
The default parameter value to return if no parameter with the
specified name was included in this request.
(RT EXPR)
|
|
Back to top resource -
Load a web application resource and make it available as a bean.
|
Retrieve the value of the specified web application resource, and make
it available as either a InputStream or a String ,
depending on the value of the input attribute.
If a problem occurs while retrieving the specified resource, a
request time exception will be thrown.
| Attribute Name | Description |
---|
id |
Specifies the name of the scripting variable (and associated page
scope attribute) that will be made available with the value of the
specified web application resource.
(REQUIRED)
| input |
If any arbitrary value for this attribute is specified, the resource
will be made available as an InputStream . If this
attribute is not specified, the resource will be made available
as a String .
(RT EXPR)
| name |
Application-relative name (starting with a '/') of the web application
resource to be loaded and made available.
(REQUIRED)
(RT EXPR)
|
|
Back to top size -
Define a bean containing the number of elements in a Collection or Map.
|
Given a reference to an array, Collection or Map, creates a new bean, of
type java.lang.Integer , whose value is the number of elements
in that collection. You can specify the collection to be counted in any
one of the following ways:
- As a runtime expression specified as the value of the
collection attribute.
- As a JSP bean specified by the
name attribute.
- As the property, specified by the
property attribute,
of the JSP bean specified by the name attribute.
| Attribute Name | Description |
---|
collection |
A runtime expression that evaluates to an array, a Collection, or
a Map.
(RT EXPR)
| id |
The name of a page scope JSP bean, of type
java.lang.Integer , that will be created to contain the
size of the underlying collection being counted.
(REQUIRED)
| name |
The name of the JSP bean (optionally constrained to the scope
specified by the scope attribute) that contains the
collection to be counted (if property is not specified),
or whose property getter is called to return the collection to be
counted (if property is specified.
(RT EXPR)
| property |
The name of the property, of the bean specified by the
name attribute, whose getter method will return the
collection to be counted.
(RT EXPR)
| scope |
The bean scope within which to search for the JSP bean specified
by the name attribute. If not specified, the available
scopes are searched in ascending sequence.
(RT EXPR)
|
|
Back to top struts -
Expose a named Struts internal configuration object as a bean.
|
Retrieve the value of the specified Struts internal configuration
object, and define it as a scripting variable and as a page scope
attribute accessible to the remainder of the current page. You must
specify exactly one of the formBean , forward ,
and mapping attributes to select the configuration object
to be exposed.
If a problem occurs while retrieving the specified configuration
object, a request time exception will be thrown.
| Attribute Name | Description |
---|
formBean |
Specifies the name of the Struts ActionFormBean
definition object to be exposed.
(RT EXPR)
| forward |
Specifies the name of the global Struts ActionForward
definition object to be exposed.
(RT EXPR)
| id |
Specifies the name of the scripting variable (and associated
page scope attribute) that will be made available with the value of
the specified Struts internal configuration object.
(REQUIRED)
| mapping |
Specifies the matching path of the Struts ActionMapping
definition object to be exposed.
(RT EXPR)
|
|
Back to top write -
Render the value of the specified bean property to the current
JspWriter.
|
Retrieve the value of the specified bean property, and render it to the
current JspWriter as a String by the ways:
- If
format attribute exists then value will be formatted on base of format
string from format attribute and default system locale.
- If in resources exists format string for value data type (view
format
attribute description) then value will be formatted on base of format string
from resources. Resources bundle and target locale can be specified with
bundle and locale attributes. If nothing specified then
default resource bundle and current user locale will be used.
- If there is a PropertyEditor configured for the property value's class, the
getAsText() method will be called.
- Otherwise, the usual
toString() conversions will be applied.
If a problem occurs while retrieving the specified bean property, a
request time exception will be thrown.
| Attribute Name | Description |
---|
bundle |
The name of the application scope bean under which the
MessageResources object containing our messages
is stored.
[Action.MESSAGES_KEY]
(RT EXPR)
| filter |
If this attribute is set to true , the rendered property
value will be filtered for characters that are sensitive in HTML, and any
such characters will be replaced by their entity equivalents.
[true]
(RT EXPR)
| format |
Specifies the format string to use to convert bean or property value
to the String . If nothing specified, then default format
string for value data type will be searched in message resources by
according key.
(RT EXPR)
| formatKey |
Specifies the key to search format string in application resources.
(RT EXPR)
| ignore |
If this attribute is set to true , and the bean specified
by the name and scope attributes does not
exist, simply return without writing anything. If this attribute is
set to false , a runtime exception to be thrown,
consistent with the other tags in this tag library.
[false]
(RT EXPR)
| locale |
The name of the session scope bean under which our currently
selected Locale object is stored.
[Action.LOCALE_KEY]
(RT EXPR)
| name |
Specifies the attribute name of the bean whose property is accessed
to retrieve the value specified by property (if
specified). If property is not specified, the value of
this bean itself will be rendered.
(REQUIRED)
(RT EXPR)
| property |
Specifies the name of the property to be accessed on the bean
specified by name . This value may be a simple, indexed,
or nested property reference expression. If not specified, the bean
identified by name will itself be rendered. If the
specified property returns null, no output will be rendered.
(RT EXPR)
| scope |
Specifies the variable scope searched to retrieve the bean specified
by name . If not specified, the default rules applied by
PageContext.findAttribute() are applied.
(RT EXPR)
|
|
Back to top
|