org.apache.taglibs.standard.tag.el.core.ExpressionUtil Maven / Gradle / Ivy
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/*
* Copyright (c) 1997-2018 Oracle and/or its affiliates. All rights reserved.
* Copyright 2004 The Apache Software Foundation
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.taglibs.standard.tag.el.core;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.PageContext;
import javax.servlet.jsp.tagext.Tag;
import org.apache.taglibs.standard.lang.support.ExpressionEvaluatorManager;
import org.apache.taglibs.standard.tag.common.core.NullAttributeException;
/**
* Contains some static utilities to facilitate common forms of
* expression evaluation.
*
* @author Shawn Bayern
*/
public class ExpressionUtil {
/** Evaluates an expression if present, but does not allow the expression
* to evaluate to 'null', throwing a NullAttributeException if it
* does. The function can return null, however, if the
* expression itself is null.
*/
public static Object evalNotNull(String tagName,
String attributeName,
String expression,
Class expectedType,
Tag tag,
PageContext pageContext)
throws JspException {
if (expression != null) {
Object r = ExpressionEvaluatorManager.evaluate(
attributeName, expression, expectedType, tag, pageContext);
if (r == null)
throw new NullAttributeException(tagName, attributeName);
return r;
} else
return null;
}
}