001/* 002 * (C) Copyright 2007 Nuxeo SA (http://nuxeo.com/) and others. 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); 005 * you may not use this file except in compliance with the License. 006 * You may obtain a copy of the License at 007 * 008 * http://www.apache.org/licenses/LICENSE-2.0 009 * 010 * Unless required by applicable law or agreed to in writing, software 011 * distributed under the License is distributed on an "AS IS" BASIS, 012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 013 * See the License for the specific language governing permissions and 014 * limitations under the License. 015 * 016 * Contributors: 017 * Nuxeo - initial API and implementation 018 * 019 * $Id: ComponentTagUtils.java 28610 2008-01-09 17:13:52Z sfermigier $ 020 */ 021 022package org.nuxeo.ecm.platform.ui.web.util; 023 024import javax.el.ELContext; 025import javax.el.ELException; 026import javax.el.ExpressionFactory; 027import javax.el.ValueExpression; 028import javax.faces.application.Application; 029import javax.faces.context.FacesContext; 030import javax.faces.view.facelets.FaceletContext; 031 032import org.apache.commons.logging.Log; 033import org.apache.commons.logging.LogFactory; 034 035/** 036 * Component tag utils. 037 * 038 * @author <a href="mailto:at@nuxeo.com">Anahide Tchertchian</a> 039 */ 040public final class ComponentTagUtils { 041 042 private static final Log log = LogFactory.getLog(ComponentTagUtils.class); 043 044 // Utility class. 045 private ComponentTagUtils() { 046 } 047 048 /** 049 * Returns true if the specified value contains a value expression, e.g the start and end of EL markers. 050 * 051 * @param value the value to evaluate, returns false if null 052 */ 053 public static boolean isValueReference(String value) { 054 if (value == null) { 055 return false; 056 } 057 return value.contains("#{") && value.indexOf("#{") < value.indexOf('}') || value.contains("${") 058 && value.indexOf("${") < value.indexOf('}'); 059 } 060 061 /** 062 * Returns true if the specified value is a value expression, e.g starting and ending with EL markers after being 063 * trimmed. 064 * 065 * @param value the value to evaluate, returns false if null 066 * @since 5.6 067 */ 068 public static boolean isStrictValueReference(String value) { 069 if (value == null) { 070 return false; 071 } 072 value = value.trim(); 073 return (value.startsWith("#{") && value.indexOf("#{") < value.indexOf('}') && value.endsWith("}")) 074 || (value.startsWith("${") && value.indexOf("${") < value.indexOf('}') && value.endsWith("}")); 075 } 076 077 /** 078 * Returns a value name for given strict value reference. If reference is #{foo} or ${foo}, will return "foo". 079 * 080 * @since 5.6 081 * @throws IllegalArgumentException if reference is null or {@link #isStrictValueReference(String)} returns false. 082 * @param valueReference 083 */ 084 public static String getBareValueName(String valueReference) { 085 if (!isStrictValueReference(valueReference)) { 086 throw new IllegalArgumentException("Invalid value reference '" + valueReference + "'"); 087 } 088 return valueReference.substring(2, valueReference.length() - 1); 089 } 090 091 /** 092 * Resolves an expression from a given faces context. 093 * <p> 094 * Resolves the expression a second time when first resolution gives a String value using the EL Expression syntax. 095 * <p> 096 * Does not throw any error when resolution fails (only logs an error message). 097 * 098 * @see #resolveElExpression(FaceletContext, String) 099 */ 100 public static Object resolveElExpression(FacesContext context, String elExpression) { 101 if (!isValueReference(elExpression)) { 102 // literal 103 return elExpression; 104 } else { 105 if (context == null) { 106 log.error("FacesContext is null => cannot resolve el expression '" + elExpression + "'"); 107 return null; 108 } 109 // expression => evaluate 110 Application app = context.getApplication(); 111 try { 112 return app.evaluateExpressionGet(context, elExpression, Object.class); 113 } catch (ELException e) { 114 log.error("Faces context: Error processing expression '" + elExpression + "'", e); 115 return null; 116 } 117 } 118 } 119 120 /** 121 * Resolves given value expression as string and sets given value on it. 122 * 123 * @since 6.0 124 */ 125 public static void applyValueExpression(FacesContext context, String elExpression, Object value) { 126 if (!isStrictValueReference(elExpression)) { 127 log.warn("Cannot set value '" + value + "' for expression '" + elExpression + "'"); 128 } else { 129 if (context == null) { 130 log.error("FacesContext is null => cannot resolve el expression '" + elExpression + "'"); 131 return; 132 } 133 Application app = context.getApplication(); 134 ExpressionFactory eFactory = app.getExpressionFactory(); 135 ELContext elContext = context.getELContext(); 136 try { 137 ValueExpression vExpression = eFactory.createValueExpression(elContext, elExpression, Object.class); 138 vExpression.setValue(elContext, value); 139 } catch (ELException e) { 140 log.error("Error setting value '" + value + "' for expression '" + elExpression + "'", e); 141 } 142 } 143 } 144 145 /** 146 * Resolves an expression from a given facelet context, using its {@link ExpressionFactory} that can hold a wider 147 * context than the faces context behind it. 148 * <p> 149 * Resolves the expression a second time when first resolution gives a String value using the EL Expression syntax. 150 * <p> 151 * Does not throw any error when resolution fails (only logs an error message). 152 */ 153 public static Object resolveElExpression(FaceletContext faceletContext, String elExpression) { 154 if (!isValueReference(elExpression)) { 155 // literal 156 return elExpression; 157 } else { 158 if (faceletContext == null) { 159 log.error("FaceletContext is null => cannot resolve el expression '" + elExpression + "'"); 160 return null; 161 } 162 // expression => evaluate 163 ExpressionFactory eFactory = faceletContext.getExpressionFactory(); 164 ELContext elContext = faceletContext.getFacesContext().getELContext(); 165 ValueExpression expr = eFactory.createValueExpression(faceletContext, elExpression, Object.class); 166 try { 167 return expr.getValue(elContext); 168 } catch (ELException e) { 169 log.error("Facelet context: Error processing expression '" + elExpression + "'", e); 170 return null; 171 } 172 } 173 } 174 175}