org.apache.taglibs.standard.lang.jstl.Evaluator Maven / Gradle / Ivy
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package org.apache.taglibs.standard.lang.jstl;
import java.text.MessageFormat;
import java.util.Map;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.PageContext;
import javax.servlet.jsp.tagext.Tag;
import org.apache.taglibs.standard.lang.support.ExpressionEvaluator;
/**
*
* This is the expression evaluator "adapter" that customizes it
* for use with the JSP Standard Tag Library. It uses a
* VariableResolver implementation that looks up variables from the
* PageContext and also implements its implicit objects. It also
* wraps ELExceptions in JspExceptions that describe the attribute
* name and value causing the error.
*
* @author Nathan Abramson - Art Technology Group
* @author Shawn Bayern
* @version $Change: 181177 $$DateTime: 2001/06/26 08:45:09 $$Author: kchung $
**/
public class Evaluator
implements ExpressionEvaluator
{
//-------------------------------------
// Properties
//-------------------------------------
//-------------------------------------
// Member variables
//-------------------------------------
/** The singleton instance of the evaluator **/
static ELEvaluator sEvaluator =
new ELEvaluator
(new JSTLVariableResolver ());
//-------------------------------------
// ExpressionEvaluator methods
//-------------------------------------
/**
*
* Translation time validation of an attribute value. This method
* will return a null String if the attribute value is valid;
* otherwise an error message.
**/
public String validate (String pAttributeName,
String pAttributeValue)
{
try {
sEvaluator.parseExpressionString (pAttributeValue);
return null;
}
catch (ELException exc) {
return
MessageFormat.format
(Constants.ATTRIBUTE_PARSE_EXCEPTION,
new Object [] {
"" + pAttributeName,
"" + pAttributeValue,
exc.getMessage ()
});
}
}
//-------------------------------------
/**
*
* Evaluates the expression at request time
**/
public Object evaluate (String pAttributeName,
String pAttributeValue,
Class pExpectedType,
Tag pTag,
PageContext pPageContext,
Map functions,
String defaultPrefix)
throws JspException
{
try {
return sEvaluator.evaluate
(pAttributeValue,
pPageContext,
pExpectedType,
functions,
defaultPrefix);
}
catch (ELException exc) {
throw new JspException
(MessageFormat.format
(Constants.ATTRIBUTE_EVALUATION_EXCEPTION,
new Object [] {
"" + pAttributeName,
"" + pAttributeValue,
exc.getMessage(),
exc.getRootCause()
}), exc.getRootCause());
}
}
/** Conduit to old-style call for convenience. */
public Object evaluate (String pAttributeName,
String pAttributeValue,
Class pExpectedType,
Tag pTag,
PageContext pPageContext)
throws JspException
{
return evaluate(pAttributeName,
pAttributeValue,
pExpectedType,
pTag,
pPageContext,
null,
null);
}
//-------------------------------------
// Testing methods
//-------------------------------------
/**
*
* Parses the given attribute value, then converts it back to a
* String in its canonical form.
**/
public static String parseAndRender (String pAttributeValue)
throws JspException
{
try {
return sEvaluator.parseAndRender (pAttributeValue);
}
catch (ELException exc) {
throw new JspException
(MessageFormat.format
(Constants.ATTRIBUTE_PARSE_EXCEPTION,
new Object [] {
"test",
"" + pAttributeValue,
exc.getMessage ()
}));
}
}
//-------------------------------------
}