001 /*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017 package org.apache.commons.el;
018
019 /**
020 *
021 * <p>An expression representing a String literal value.
022 *
023 * @author Nathan Abramson - Art Technology Group
024 * @version $Change: 181177 $$DateTime: 2001/06/26 08:45:09 $$Author: bayard $
025 **/
026
027 public class StringLiteral
028 extends Literal
029 {
030 //-------------------------------------
031 /**
032 *
033 * Constructor
034 **/
035 StringLiteral (Object pValue)
036 {
037 super (pValue);
038 }
039
040 //-------------------------------------
041 /**
042 *
043 * Returns a StringLiteral parsed from the given token (enclosed by
044 * single or double quotes)
045 **/
046 public static StringLiteral fromToken (String pToken)
047 {
048 return new StringLiteral (getValueFromToken (pToken));
049 }
050
051 //-------------------------------------
052 /**
053 *
054 * Returns a StringLiteral with the given string value
055 **/
056 public static StringLiteral fromLiteralValue (String pValue)
057 {
058 return new StringLiteral (pValue);
059 }
060
061 //-------------------------------------
062 /**
063 *
064 * Parses the given token into the literal value
065 **/
066 public static String getValueFromToken (String pToken)
067 {
068 StringBuffer buf = new StringBuffer ();
069 int len = pToken.length () - 1;
070 boolean escaping = false;
071 for (int i = 1; i < len; i++) {
072 char ch = pToken.charAt (i);
073 if (escaping) {
074 buf.append (ch);
075 escaping = false;
076 }
077 else if (ch == '\\') {
078 escaping = true;
079 }
080 else {
081 buf.append (ch);
082 }
083 }
084 return buf.toString ();
085 }
086
087 //-------------------------------------
088 /**
089 *
090 * Converts the specified value to a String token, using " as the
091 * enclosing quotes and escaping any characters that need escaping.
092 **/
093 public static String toStringToken (String pValue)
094 {
095 // See if any escaping is needed
096 if (pValue.indexOf ('\"') < 0 &&
097 pValue.indexOf ('\\') < 0) {
098 return "\"" + pValue + "\"";
099 }
100
101 // Escaping is needed
102 else {
103 StringBuffer buf = new StringBuffer ();
104 buf.append ('\"');
105 int len = pValue.length ();
106 for (int i = 0; i < len; i++) {
107 char ch = pValue.charAt (i);
108 if (ch == '\\') {
109 buf.append ('\\');
110 buf.append ('\\');
111 }
112 else if (ch == '\"') {
113 buf.append ('\\');
114 buf.append ('\"');
115 }
116 else {
117 buf.append (ch);
118 }
119 }
120 buf.append ('\"');
121 return buf.toString ();
122 }
123 }
124
125 //-------------------------------------
126 /**
127 *
128 * Converts the specified value to an identifier token, escaping it
129 * as a string literal if necessary.
130 **/
131 public static String toIdentifierToken (String pValue)
132 {
133 // See if it's a valid java identifier
134 if (isJavaIdentifier (pValue)) {
135 return pValue;
136 }
137
138 // Return as a String literal
139 else {
140 return toStringToken (pValue);
141 }
142 }
143
144 //-------------------------------------
145 /**
146 *
147 * Returns true if the specified value is a legal java identifier
148 **/
149 static boolean isJavaIdentifier (String pValue)
150 {
151 int len = pValue.length ();
152 if (len == 0) {
153 return false;
154 }
155 else {
156 if (!Character.isJavaIdentifierStart (pValue.charAt (0))) {
157 return false;
158 }
159 else {
160 for (int i = 1; i < len; i++) {
161 if (!Character.isJavaIdentifierPart (pValue.charAt (i))) {
162 return false;
163 }
164 }
165 return true;
166 }
167 }
168 }
169
170 //-------------------------------------
171 // Expression methods
172 //-------------------------------------
173 /**
174 *
175 * Returns the expression in the expression language syntax
176 **/
177 public String getExpressionString ()
178 {
179 return toStringToken ((String) getValue ());
180 }
181
182 //-------------------------------------
183 }