org.apache.struts2.components

Class IteratorComponent

java.lang.Object

org.apache.struts2.components.Component

org.apache.struts2.components.ContextBean

org.apache.struts2.components.IteratorComponent

public class IteratorComponent
extends ContextBean

Iterator will iterate over a value. An iterable value can be any of: java.util.Collection, java.util.Iterator, java.util.Enumeration, java.util.Map, or an array.

• status (String) - if specified, an instance of IteratorStatus will be pushed into stack upon each iteration
• value (Object) - the source to iterate over, must be iteratable, else the object itself will be put into a newly created List (see MakeIterator#convert(Object)
• id (String) - if specified the current iteration object will be place with this id in Struts stack's context scope
• begin (Integer) - if specified the iteration will start on that index
• end (Integer) - if specified the iteration will end on that index(inclusive)
• step (Integer) - if specified the iteration index will be increased by this value on each iteration. It can be a negative value, in which case 'begin' must be greater than 'end'

The following example retrieves the value of the getDays() method of the current object on the value stack and uses it to iterate over. The <s:property/> tag prints out the current value of the iterator.

 
 <s:iterator value="days">
   <p>day is: <s:property/></p>
 </s:iterator>
 
 

The following example uses a Bean tag and places it into the ActionContext. The iterator tag will retrieve that object from the ActionContext and then calls its getDays() method as above. The status attribute is also used to create an IteratorStatus object, which in this example, its odd() method is used to alternate row colours:

 

 <s:bean name="org.apache.struts2.example.IteratorExample" var="it">
   <s:param name="day" value="'foo'"/>
   <s:param name="day" value="'bar'"/>
 </s:bean>

 <table border="0" cellspacing="0" cellpadding="1">
 <tr>
   <th>Days of the week</th>
 </tr>

 <s:iterator value="#it.days" status="rowstatus">
   <tr>
     <s:if test="#rowstatus.odd == true">
       <td style="background: grey"><s:property/></td>
     </s:if>
     <s:else>
       <td><s:property/></td>
     </s:else>
   </tr>
 </s:iterator>
 </table>

 
 

The next example will further demonstrate the use of the status attribute, using a DAO obtained from the action class through OGNL, iterating over groups and their users (in a security context). The last() method indicates if the current object is the last available in the iteration, and if not, we need to separate the users using a comma:

 

  <s:iterator value="groupDao.groups" status="groupStatus">
      <tr class="<s:if test="#groupStatus.odd == true ">odd</s:if><s:else>even</s:else>">
          <td><s:property value="name" /></td>
          <td><s:property value="description" /></td>
          <td>
              <s:iterator value="users" status="userStatus">
                  <s:property value="fullName" /><s:if test="!#userStatus.last">,</s:if>
              </s:iterator>
          </td>
      </tr>
  </s:iterator>

 
 

The next example iterates over a an action collection and passes every iterator value to another action. The trick here lies in the use of the '[0]' operator. It takes the current iterator value and passes it on to the edit action. Using the '[0]' operator has the same effect as using <s:property />. (The latter, however, does not work from inside the param tag).

 

      <s:action name="entries" var="entries"/>
      <s:iterator value="#entries.entries" >
          <s:property value="name" />
          <s:property />
          <s:push value="...">
              <s:action name="edit" var="edit" >
                  <s:param name="entry" value="[0]" />
              </s:action>
          </push>
      </s:iterator>

 
 

A loop that iterates 5 times

 

 <s:iterator var="counter" begin="1" end="5" >
    <!-- current iteration value (1, ... 5) -->
    <s:property value="top" />
 </s:iterator>

 
 

Another way to create a simple loop, similar to JSTL's <c:forEach begin="..." end="..." ...> is to use some OGNL magic, which provides some under-the-covers magic to make 0-n loops trivial. This example also loops five times.

 

 <s:iterator status="stat" value="(5).{ #this }" >
    <s:property value="#stat.count" /> <!-- Note that "count" is 1-based, "index" is 0-based. -->
 </s:iterator>

 
 

A loop that iterates over a partial list

 

 <s:iterator value="{1,2,3,4,5}" begin="2" end="4" >
    <!-- current iteration value (2,3,4) -->
    <s:property value="top" />
 </s:iterator>

 
 

Field Summary

Fields

Modifier and Type	Field and Description
protected Integer	begin
protected String	beginStr
protected Integer	end
protected String	endStr
protected Iterator	iterator
protected Object	oldStatus
protected IteratorStatus	status
protected String	statusAttr
protected IteratorStatus.StatusState	statusState
protected Integer	step
protected String	stepStr
protected String	value

Fields inherited from class org.apache.struts2.components.ContextBean

var

Fields inherited from class org.apache.struts2.components.Component

actionMapper, COMPONENT_STACK, devMode, parameters, stack, standardAttributesMap, throwExceptionOnELFailure

Constructor Summary

Constructors

Constructor and Description
IteratorComponent(ValueStack stack)

Method Summary

Modifier and Type	Method and Description
boolean	end(Writer writer, String body) Callback for the end tag of this component.
void	setBegin(String begin)
void	setEnd(String end)
void	setStatus(String status)
void	setStep(String step)
void	setValue(String value)
boolean	start(Writer writer) Callback for the start tag of this component.

Methods inherited from class org.apache.struts2.components.ContextBean

getVar, putInContext, setVar

Methods inherited from class org.apache.struts2.components.Component

addAllParameters, addParameter, altSyntax, completeExpressionIfAltSyntax, copyParams, determineActionURL, determineNamespace, end, escapeHtmlBody, fieldError, findAncestor, findString, findString, findStringIfAltSyntax, findValue, findValue, findValue, getComponentStack, getParameters, getStack, getStandardAttributes, isValidTagAttribute, popComponentStack, setActionMapper, setDevMode, setThrowExceptionsOnELFailure, setUrlHelper, stripExpressionIfAltSyntax, toString, usesBody

Methods inherited from class java.lang.Object

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

Field Detail

iterator

protected Iterator iterator

status

protected IteratorStatus status

oldStatus

protected Object oldStatus

statusState

protected IteratorStatus.StatusState statusState

statusAttr

protected String statusAttr

value

protected String value

beginStr

protected String beginStr

begin

protected Integer begin

endStr

protected String endStr

end

protected Integer end

stepStr

protected String stepStr

step

protected Integer step

Constructor Detail

IteratorComponent

public IteratorComponent(ValueStack stack)

Method Detail

start

public boolean start(Writer writer)

Description copied from class: Component

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

Overrides:

start in class Component

Parameters:

writer - the output writer.

Returns:

true if the body should be evaluated

end

public boolean end(Writer writer,
                   String body)

Description copied from class: Component

Callback for the end tag of this component. Should the body be evaluated again?
NOTE: will pop component stack.

Overrides:

end in class Component

Parameters:

writer - the output writer.

body - the rendered body.

Returns:

true if the body should be evaluated again

setStatus

public void setStatus(String status)

setValue

public void setValue(String value)

setBegin

public void setBegin(String begin)

setEnd

public void setEnd(String end)

setStep

public void setStep(String step)