1 /* 2 * Licensed to the Apache Software Foundation (ASF) under one 3 * or more contributor license agreements. See the NOTICE file 4 * distributed with this work for additional information 5 * regarding copyright ownership. The ASF licenses this file 6 * to you under the Apache License, Version 2.0 (the 7 * "License"); you may not use this file except in compliance 8 * with the License. You may obtain a copy of the License at 9 * 10 * http://www.apache.org/licenses/LICENSE-2.0 11 * 12 * Unless required by applicable law or agreed to in writing, 13 * software distributed under the License is distributed on an 14 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY 15 * KIND, either express or implied. See the License for the 16 * specific language governing permissions and limitations 17 * under the License. 18 */ 19 package org.apache.myfaces.util; 20 21 /** 22 * Utilities for determining the current container and for the unified 23 * expression language. 24 * 25 */ 26 public class ContainerUtils 27 { 28 /** 29 * Determines whether we're running in a Servlet 2.5/JSP 2.1 environment. 30 * 31 * @return <code>true</code> if we're running in a JSP 2.1 environment, 32 * <code>false</code> otherwise 33 */ 34 public static boolean isJsp21() 35 { 36 try 37 { 38 // simply check if the class JspApplicationContext is available 39 Class.forName("javax.servlet.jsp.JspApplicationContext"); 40 return true; 41 } 42 catch (ClassNotFoundException ex) 43 { 44 ; // expected exception in a JSP 2.0 (or less) environment 45 } 46 47 return false; 48 } 49 50 /** 51 * Return true if the specified string contains an EL expression. 52 * 53 * <p> 54 * <strong>NOTICE</strong> This method is just a copy of 55 * {@link UIComponentTag#isValueReference(String)}, but it's required 56 * because the class UIComponentTag depends on a JSP 2.1 container 57 * (for example, it indirectly implements the interface JspIdConsumer) 58 * and therefore internal classes shouldn't access this class. That's 59 * also the reason why this method is inside the class ContainerUtils, 60 * because it allows MyFaces to be independent of a JSP 2.1 container. 61 * </p> 62 */ 63 public static boolean isValueReference(String value) 64 { 65 if (value == null) { 66 throw new NullPointerException("value"); 67 } 68 69 int start = value.indexOf("#{"); 70 if (start < 0) { 71 return false; 72 } 73 74 int end = value.lastIndexOf('}'); 75 return (end >=0 && start < end); 76 } 77 }