| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You 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.util; |
| |
| import jakarta.el.ExpressionFactory; |
| import jakarta.el.ValueExpression; |
| import jakarta.servlet.jsp.JspApplicationContext; |
| import jakarta.servlet.jsp.JspFactory; |
| import jakarta.servlet.jsp.PageContext; |
| |
| /** |
| * Helper functions for working with EL expressions. |
| */ |
| public class ExpressionUtil { |
| |
| /** |
| * Create a value expression. |
| * |
| * @param pageContext the context in which the expression will be parsed |
| * @param expression the expression |
| * @param expectedType the expected type of result |
| * @return a parsed expression |
| */ |
| public static ValueExpression createValueExpression(PageContext pageContext, String expression, Class<?> expectedType) { |
| ExpressionFactory factory = getExpressionFactory(pageContext); |
| return factory.createValueExpression(pageContext.getELContext(), expression, expectedType); |
| } |
| |
| /** |
| * Return the JSP's ExpressionFactory. |
| * |
| * @param pageContext the context for the JSP |
| * @return the ExpressionFactory to use for EL expressions in that JSP |
| */ |
| public static ExpressionFactory getExpressionFactory(PageContext pageContext) { |
| JspApplicationContext appContext = JspFactory.getDefaultFactory().getJspApplicationContext(pageContext.getServletContext()); |
| return appContext.getExpressionFactory(); |
| } |
| |
| /** |
| * Evaluate a value expression. To support optional attributes, if the expression is null then |
| * null will be returned. |
| * |
| * @param expression the expression |
| * @param pageContext the context for the JSP |
| * @param <T> the expected type of the expression |
| * @return the result of evaluating the expression |
| */ |
| public static <T> T evaluate(ValueExpression expression, PageContext pageContext) { |
| if (expression == null) { |
| return null; |
| } |
| @SuppressWarnings("unchecked") |
| T value = (T) expression.getValue(pageContext.getELContext()); |
| return value; |
| } |
| |
| public static boolean evaluate(ValueExpression expression, PageContext pageContext, boolean fallback) { |
| if (expression == null) { |
| return fallback; |
| } |
| Boolean result = (Boolean) expression.getValue(pageContext.getELContext()); |
| return result == null ? fallback : result; |
| } |
| |
| public static int evaluate(ValueExpression expression, PageContext pageContext, int fallback) { |
| if (expression == null) { |
| return fallback; |
| } |
| Integer result = (Integer) expression.getValue(pageContext.getELContext()); |
| return result == null ? fallback : result; |
| } |
| } |