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package org.apache.taglibs.standard.tag.el.core;
import java.util.ArrayList;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.jstl.core.LoopTag;
import javax.servlet.jsp.tagext.IterationTag;
import org.apache.taglibs.standard.lang.support.ExpressionEvaluatorManager;
import org.apache.taglibs.standard.tag.common.core.ForEachSupport;
import org.apache.taglibs.standard.tag.common.core.NullAttributeException;
/**
* <p>A handler for <forEach> that accepts attributes as Strings
* and evaluates them as expressions at runtime.</p>
*
* @author Shawn Bayern
*/
public class ForEachTag
extends ForEachSupport
implements LoopTag, IterationTag
{
//*********************************************************************
// 'Private' state (implementation details)
private String begin_; // stores EL-based property
private String end_; // stores EL-based property
private String step_; // stores EL-based property
private String items_; // stores EL-based property
//*********************************************************************
// Constructor
public ForEachTag() {
super();
init();
}
//*********************************************************************
// Tag logic
/* Begins iterating by processing the first item. */
public int doStartTag() throws JspException {
// evaluate any expressions we were passed, once per invocation
evaluateExpressions();
// chain to the parent implementation
return super.doStartTag();
}
// Releases any resources we may have (or inherit)
public void release() {
super.release();
init();
}
//*********************************************************************
// Accessor methods
// for EL-based attribute
public void setBegin(String begin_) {
this.begin_ = begin_;
this.beginSpecified = true;
}
// for EL-based attribute
public void setEnd(String end_) {
this.end_ = end_;
this.endSpecified = true;
}
// for EL-based attribute
public void setStep(String step_) {
this.step_ = step_;
this.stepSpecified = true;
}
public void setItems(String items_) {
this.items_ = items_;
}
//*********************************************************************
// Private (utility) methods
// (re)initializes state (during release() or construction)
private void init() {
// defaults for interface with page author
begin_ = null; // (no expression)
end_ = null; // (no expression)
step_ = null; // (no expression)
items_ = null; // (no expression)
}
/* Evaluates expressions as necessary */
private void evaluateExpressions() throws JspException {
/*
* Note: we don't check for type mismatches here; we assume
* the expression evaluator will return the expected type
* (by virtue of knowledge we give it about what that type is).
* A ClassCastException here is truly unexpected, so we let it
* propagate up.
*/
if (begin_ != null) {
Object r = ExpressionEvaluatorManager.evaluate(
"begin", begin_, Integer.class, this, pageContext);
if (r == null)
throw new NullAttributeException("forEach", "begin");
begin = ((Integer) r).intValue();
validateBegin();
}
if (end_ != null) {
Object r = ExpressionEvaluatorManager.evaluate(
"end", end_, Integer.class, this, pageContext);
if (r == null)
throw new NullAttributeException("forEach", "end");
end = ((Integer) r).intValue();
validateEnd();
}
if (step_ != null) {
Object r = ExpressionEvaluatorManager.evaluate(
"step", step_, Integer.class, this, pageContext);
if (r == null)
throw new NullAttributeException("forEach", "step");
step = ((Integer) r).intValue();
validateStep();
}
if (items_ != null) {
rawItems = ExpressionEvaluatorManager.evaluate(
"items", items_, Object.class, this, pageContext);
// use an empty list to indicate "no iteration", if relevant
if (rawItems == null)
rawItems = new ArrayList();
}
}
}
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