1. /*
  2. * The Apache Software License, Version 1.1
  3. *
  4. * Copyright (c) 1999 The Apache Software Foundation. All rights
  5. * reserved.
  6. *
  7. * Redistribution and use in source and binary forms, with or without
  8. * modification, are permitted provided that the following conditions
  9. * are met:
  10. *
  11. * 1. Redistributions of source code must retain the above copyright
  12. * notice, this list of conditions and the following disclaimer.
  13. *
  14. * 2. Redistributions in binary form must reproduce the above copyright
  15. * notice, this list of conditions and the following disclaimer in
  16. * the documentation and/or other materials provided with the
  17. * distribution.
  18. *
  19. * 3. The end-user documentation included with the redistribution, if
  20. * any, must include the following acknowlegement:
  21. * "This product includes software developed by the
  22. * Apache Software Foundation (http://www.apache.org/)."
  23. * Alternately, this acknowlegement may appear in the software itself,
  24. * if and wherever such third-party acknowlegements normally appear.
  25. *
  26. * 4. The names "The Jakarta Project", "Tomcat", and "Apache Software
  27. * Foundation" must not be used to endorse or promote products derived
  28. * from this software without prior written permission. For written
  29. * permission, please contact apache@apache.org.
  30. *
  31. * 5. Products derived from this software may not be called "Apache"
  32. * nor may "Apache" appear in their names without prior written
  33. * permission of the Apache Group.
  34. *
  35. * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
  36. * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  37. * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  38. * DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
  39. * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  40. * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  41. * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
  42. * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  43. * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  44. * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  45. * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  46. * SUCH DAMAGE.
  47. * ====================================================================
  48. *
  49. * This software consists of voluntary contributions made by many
  50. * individuals on behalf of the Apache Software Foundation. For more
  51. * information on the Apache Software Foundation, please see
  52. * <http://www.apache.org/>.
  53. *
  54. */
  55. package org.apache.commons.el;
  56. import java.lang.reflect.Array;
  57. import java.util.Collection;
  58. import java.util.Map;
  59. import javax.servlet.jsp.el.ELException;
  60. /**
  61. *
  62. * <p>The implementation of the empty operator
  63. *
  64. * @author Nathan Abramson - Art Technology Group
  65. * @version $Change: 181177 $$DateTime: 2001/06/26 08:45:09 $$Author: luehe $
  66. **/
  67. public class EmptyOperator
  68. extends UnaryOperator
  69. {
  70. //-------------------------------------
  71. // Singleton
  72. //-------------------------------------
  73. public static final EmptyOperator SINGLETON =
  74. new EmptyOperator ();
  75. //-------------------------------------
  76. /**
  77. *
  78. * Constructor
  79. **/
  80. public EmptyOperator ()
  81. {
  82. }
  83. //-------------------------------------
  84. // Expression methods
  85. //-------------------------------------
  86. /**
  87. *
  88. * Returns the symbol representing the operator
  89. **/
  90. public String getOperatorSymbol ()
  91. {
  92. return "empty";
  93. }
  94. //-------------------------------------
  95. /**
  96. *
  97. * Applies the operator to the given value
  98. **/
  99. public Object apply (Object pValue,
  100. Logger pLogger)
  101. throws ELException
  102. {
  103. // See if the value is null
  104. if (pValue == null) {
  105. return PrimitiveObjects.getBoolean (true);
  106. }
  107. // See if the value is a zero-length String
  108. else if ("".equals (pValue)) {
  109. return PrimitiveObjects.getBoolean (true);
  110. }
  111. // See if the value is a zero-length array
  112. else if (pValue.getClass ().isArray () &&
  113. Array.getLength (pValue) == 0) {
  114. return PrimitiveObjects.getBoolean (true);
  115. }
  116. // See if the value is an empty Map
  117. else if (pValue instanceof Map &&
  118. ((Map) pValue).isEmpty ()) {
  119. return PrimitiveObjects.getBoolean (true);
  120. }
  121. // See if the value is an empty Collection
  122. else if (pValue instanceof Collection &&
  123. ((Collection) pValue).isEmpty ()) {
  124. return PrimitiveObjects.getBoolean (true);
  125. }
  126. // Otherwise, not empty
  127. else {
  128. return PrimitiveObjects.getBoolean (false);
  129. }
  130. }
  131. //-------------------------------------
  132. }