org.apache.struts2.components
类 Param

java.lang.Object
  org.apache.struts2.components.Component
      org.apache.struts2.components.Param

public class Param
extends Component

This tag can be used to parameterize other tags.

The include tag and bean tag are examples of such tags.

The parameters can be added with or without a name as key. If the tag provides a name attribute the parameters are added using the addParamter method. For unnamed parameters the Tag must implement the Param.UnnamedParametric interface defined in this class (e.g. The TextTag does this).

This tag has the following two paramters.

• name (String) - the name of the parameter
• value (Object) - the value of the parameter
• suppressEmptyParameters (boolean) - whether to suppress empty parameters

Note: When you declare the param tag, the value can be defined in either a value attribute or as text between the start and end tag. Struts behaves a bit different according to these two situations. This is best illustrated using an example:
<param name="color">blue</param> <-- (A) -->
<param name="color" value="blue"/> <-- (B) -->
In the first situation (A) the value would be evaluated to the stack as a java.lang.String object. And in situation (B) the value would be evaluated to the stack as a java.lang.Object object.
For more information see WW-808.

Examples

 <ui:component>
  <ui:param name="key"     value="[0]"/>
  <ui:param name="value"   value="[1]"/>
  <ui:param name="context" value="[2]"/>
 </ui:component>
 

Whether to suppress empty parameters:

 <s:a action="eventAdd" accesskey="a">
   <s:text name="title.heading.eventadd" />
   <s:param name="bean.searchString" value="%{bean.searchString}" />
   <s:param name="bean.filter" value="%{bean.filter}" />
   <s:param name="bean.pageNum" value="%{pager.pageNumber}" />
   <s:param name="suppressEmptyParameters" value="true"/>
 </s:a>
 

where the key will be the identifier and the value the result of an OGNL expression run against the current ValueStack.

This second example demonstrates how the text tag can use parameters from this param tag.

 <s:text name="cart.total.cost">
     <s:param value="#session.cartTotal"/>
 </s:text>
 

另请参见：

Include, Bean, Text

嵌套类摘要

static interface

Param.UnnamedParametric Tags can implement this to support nested param tags without the name attribute.

字段摘要

从类 org.apache.struts2.components.Component 继承的字段

COMPONENT_STACK

构造方法摘要

Param(com.opensymphony.xwork2.util.ValueStack stack)

方法摘要

boolean	end(Writer writer, String body) Callback for the end tag of this component.
void	setName(String name)
void	setSuppressEmptyParameters(boolean suppressEmptyParameters)
void	setValue(String value)
boolean	usesBody() Overwrite to set if body should be used.

从类 org.apache.struts2.components.Component 继承的方法

addAllParameters, addParameter, altSyntax, copyParams, getComponentStack, getParameters, getStack, setActionMapper, setThrowExceptionsOnELFailure, setUrlHelper, start

从类 java.lang.Object 继承的方法

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

构造方法详细信息

Param

public Param(com.opensymphony.xwork2.util.ValueStack stack)

方法详细信息

end

public boolean end(Writer writer,
                   String body)

从类 Component 复制的描述

Callback for the end tag of this component. Should the body be evaluated again?

NOTE: will pop component stack.

覆盖：

类 Component 中的 end

参数：

writer - the output writer.

body - the rendered body.

返回：

true if the body should be evaluated again

usesBody

public boolean usesBody()

从类 Component 复制的描述

Overwrite to set if body should be used.

覆盖：

类 Component 中的 usesBody

返回：

always false for this component.

setName

public void setName(String name)

setValue

public void setValue(String value)

setSuppressEmptyParameters

public void setSuppressEmptyParameters(boolean suppressEmptyParameters)