001: /*
002: * The Apache Software License, Version 1.1
003: *
004: * Copyright (c) 1999 The Apache Software Foundation. All rights
005: * reserved.
006: *
007: * Redistribution and use in source and binary forms, with or without
008: * modification, are permitted provided that the following conditions
009: * are met:
010: *
011: * 1. Redistributions of source code must retain the above copyright
012: * notice, this list of conditions and the following disclaimer.
013: *
014: * 2. Redistributions in binary form must reproduce the above copyright
015: * notice, this list of conditions and the following disclaimer in
016: * the documentation and/or other materials provided with the
017: * distribution.
018: *
019: * 3. The end-user documentation included with the redistribution, if
020: * any, must include the following acknowlegement:
021: * "This product includes software developed by the
022: * Apache Software Foundation (http://www.apache.org/)."
023: * Alternately, this acknowlegement may appear in the software itself,
024: * if and wherever such third-party acknowlegements normally appear.
025: *
026: * 4. The names "The Jakarta Project", "Tomcat", and "Apache Software
027: * Foundation" must not be used to endorse or promote products derived
028: * from this software without prior written permission. For written
029: * permission, please contact apache@apache.org.
030: *
031: * 5. Products derived from this software may not be called "Apache"
032: * nor may "Apache" appear in their names without prior written
033: * permission of the Apache Group.
034: *
035: * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
036: * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
037: * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
038: * DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
039: * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
040: * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
041: * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
042: * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
043: * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
044: * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
045: * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
046: * SUCH DAMAGE.
047: * ====================================================================
048: *
049: * This software consists of voluntary contributions made by many
050: * individuals on behalf of the Apache Software Foundation. For more
051: * information on the Apache Software Foundation, please see
052: * <http://www.apache.org/>.
053: *
054: */
055:
056: package org.apache.commons.el;
057:
058: import java.lang.reflect.Array;
059: import java.util.Collection;
060: import java.util.Map;
061: import javax.servlet.jsp.el.ELException;
062:
063: /**
064: *
065: * <p>The implementation of the empty operator
066: *
067: * @author Nathan Abramson - Art Technology Group
068: * @version $Change: 181177 $$DateTime: 2001/06/26 08:45:09 $$Author: luehe $
069: **/
070:
071: public class EmptyOperator extends UnaryOperator {
072: //-------------------------------------
073: // Singleton
074: //-------------------------------------
075:
076: public static final EmptyOperator SINGLETON = new EmptyOperator();
077:
078: //-------------------------------------
079: /**
080: *
081: * Constructor
082: **/
083: public EmptyOperator() {
084: }
085:
086: //-------------------------------------
087: // Expression methods
088: //-------------------------------------
089: /**
090: *
091: * Returns the symbol representing the operator
092: **/
093: public String getOperatorSymbol() {
094: return "empty";
095: }
096:
097: //-------------------------------------
098: /**
099: *
100: * Applies the operator to the given value
101: **/
102: public Object apply(Object pValue, Logger pLogger)
103: throws ELException {
104: // See if the value is null
105: if (pValue == null) {
106: return PrimitiveObjects.getBoolean(true);
107: }
108:
109: // See if the value is a zero-length String
110: else if ("".equals(pValue)) {
111: return PrimitiveObjects.getBoolean(true);
112: }
113:
114: // See if the value is a zero-length array
115: else if (pValue.getClass().isArray()
116: && Array.getLength(pValue) == 0) {
117: return PrimitiveObjects.getBoolean(true);
118: }
119:
120: // See if the value is an empty Map
121: else if (pValue instanceof Map && ((Map) pValue).isEmpty()) {
122: return PrimitiveObjects.getBoolean(true);
123: }
124:
125: // See if the value is an empty Collection
126: else if (pValue instanceof Collection
127: && ((Collection) pValue).isEmpty()) {
128: return PrimitiveObjects.getBoolean(true);
129: }
130:
131: // Otherwise, not empty
132: else {
133: return PrimitiveObjects.getBoolean(false);
134: }
135: }
136:
137: //-------------------------------------
138: }
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