- All Implemented Interfaces:
public abstract class LoopTagSupport extends TagSupport implements LoopTag, IterationTag, TryCatchFinally
Base support class to facilitate implementation of iteration tags.
Since most iteration tags will behave identically with respect to actual iterative behavior, JSTL provides this base support class to facilitate implementation. Many iteration tags will extend this and merely implement the hasNext() and next() methods to provide contents for the handler to iterate over.
In particular, this base class provides support for:
- Iteration control, based on protected prepare(), next(), and hasNext() methods
- Subsetting (begin, end, step>functionality, including validation of subset parameters for sensibility)
- item retrieval (getCurrent())
- status retrieval (LoopTagStatus)
- exposing attributes (set by var and varStatus attributes)
In providing support for these tasks, LoopTagSupport contains certain control variables that act to modify the iteration. Accessors are provided for these control variables when the variables represent information needed or wanted at translation time (e.g., var, varStatus). For other variables, accessors cannot be provided here since subclasses may differ on their implementations of how those accessors are received. For instance, one subclass might accept a String and convert it into an object of a specific type by using an expression evaluator; others might accept objects directly. Still others might not want to expose such information to outside control.
- See Also:
- Serialized Form
Constructors Constructor Description
LoopTagSupport()Constructs a new LoopTagSupport.
All Methods Instance Methods Concrete Methods Modifier and Type Method Description
doAfterBody()Continues the iteration when appropriate -- that is, if we (a) have more items and (b) don't run over our 'end' (given our 'step').
doCatch(java.lang.Throwable t)Rethrows the given Throwable.
doFinally()Removes any attributes that this LoopTagSupport set.
doStartTag()Begins iterating by processing the first item.
getCurrent()Retrieves the current item in the iteration.
getLoopStatus()Retrieves a 'status' object to provide information about the current round of the iteration.
release()Releases any resources this LoopTagSupport may have (or inherit).
setVar(java.lang.String id)Sets the 'var' attribute.
setVarStatus(java.lang.String statusId)Sets the 'varStatus' attribute.
Methods inherited from class javax.servlet.jsp.tagext.TagSupport
doEndTag, findAncestorWithClass, getId, getParent, getValue, getValues, removeValue, setId, setPageContext, setParent, setValue
Methods inherited from class java.lang.Object
equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
public void release()Releases any resources this LoopTagSupport may have (or inherit).
public int doStartTag() throws JspExceptionBegins iterating by processing the first item.
public int doAfterBody() throws JspExceptionContinues the iteration when appropriate -- that is, if we (a) have more items and (b) don't run over our 'end' (given our 'step').
public void doFinally()Removes any attributes that this LoopTagSupport set.
These attributes are intended to support scripting variables with NESTED scope, so we don't want to pollute attribute space by leaving them lying around.
public void doCatch(java.lang.Throwable t) throws java.lang.ThrowableRethrows the given Throwable.
public java.lang.Object getCurrent()Description copied from interface:
LoopTagRetrieves the current item in the iteration. Behaves idempotently; calling getCurrent() repeatedly should return the same Object until the iteration is advanced. (Specifically, calling getCurrent() does not advance the iteration.)
public LoopTagStatus getLoopStatus()Description copied from interface:
LoopTagRetrieves a 'status' object to provide information about the current round of the iteration.
public void setVar(java.lang.String id)Sets the 'var' attribute.
id- Name of the exported scoped variable storing the current item of the iteration.
public void setVarStatus(java.lang.String statusId)Sets the 'varStatus' attribute.
statusId- Name of the exported scoped variable storing the status of the iteration.