Coercion


1   /*
2    * Copyright 2002,2004 The Apache Software Foundation.
3    *
4    * Licensed under the Apache License, Version 2.0 (the "License");
5    * you may not use this file except in compliance with the License.
6    * You may obtain a copy of the License at
7    *
8    *      http://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS,
12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   * See the License for the specific language governing permissions and
14   * limitations under the License.
15   */
16  package org.apache.commons.jexl.util;
17  
18  /**
19   *  Coercion utilities for the JSTL EL-like coercion.
20   *
21   *  @since 1.0
22   *  @author <a HREF="mailto:geirm@apache.org">Geir Magnusson Jr.</a>
23   */
24  public class Coercion {
25  
26      /**
27       * Coerce to a Boolean.
28       *
29       * @param val Object to be coerced.
30       * @return The Boolean coerced value, or null if none possible.
31       */
32      public static Boolean   coerceBoolean(Object   val) {
33          if (val == null) {
34              return Boolean.FALSE;
35          } else if (val instanceof Boolean  ) {
36              return (Boolean  ) val;
37          } else if (val instanceof String  ) {
38              return Boolean.valueOf((String  ) val);
39          }
40          return null;
41      }
42  
43      /**
44       * Coerce to a Integer.
45       *
46       * @param val Object to be coerced.
47       * @return The Integer coerced value.
48       * @throws Exception If Integer coercion fails.
49       */
50      public static Integer   coerceInteger(Object   val)
51      throws Exception   {
52          if (val == null) {
53              return new Integer  (0);
54          } else if (val instanceof String  ) {
55              if ("".equals(val)) {
56                  return new Integer  (0);
57              }
58              return Integer.valueOf((String  ) val);
59          } else if (val instanceof Character  ) {
60              return new Integer  (((Character  ) val).charValue());
61          } else if (val instanceof Boolean  ) {
62              throw new Exception  ("Boolean->Integer coercion exception");
63          } else if (val instanceof Number  ) {
64              return new Integer  (((Number  ) val).intValue());
65          }
66  
67          throw new Exception  ("Integer coercion exception");
68      }
69  
70      /**
71       * Coerce to a Long.
72       *
73       * @param val Object to be coerced.
74       * @return The Long coerced value.
75       * @throws Exception If Long coercion fails.
76       */
77      public static Long   coerceLong(Object   val)
78      throws Exception   {
79          if (val == null) {
80              return new Long  (0);
81          } else if (val instanceof String  ) {
82              if ("".equals(val)) {
83                  return new Long  (0);
84              }
85              return Long.valueOf((String  ) val);
86          } else if (val instanceof Character  ) {
87              return new Long  (((Character  ) val).charValue());
88          } else if (val instanceof Boolean  ) {
89              throw new Exception  ("Boolean->Long coercion exception");
90          } else if (val instanceof Number  ) {
91              return new Long  (((Number  ) val).longValue());
92          }
93  
94          throw new Exception  ("Long coercion exception");
95      }
96  
97      /**
98       * Coerce to a Double.
99       *
100      * @param val Object to be coerced.
101      * @return The Double coerced value.
102      * @throws Exception If Double coercion fails.
103      */
104     public static Double   coerceDouble(Object   val)
105     throws Exception   {
106         if (val == null) {
107             return new Double  (0);
108         } else if (val instanceof String  ) {
109             if ("".equals(val)) {
110                 return new Double  (0);
111             }
112 
113             /*
114              * the spec seems to be iffy about this.  Going to give it a wack
115              *  anyway
116              */
117 
118             return new Double  ((String  ) val);
119         } else if (val instanceof Character  ) {
120             int i = ((Character  ) val).charValue();
121 
122             return new Double  (Double.parseDouble(String.valueOf(i)));
123         } else if (val instanceof Boolean  ) {
124             throw new Exception  ("Boolean->Double coercion exception");
125         } else if (val instanceof Double  ) {
126             return (Double  ) val;
127         } else if (val instanceof Number  ) {
128             //The below construct is used rather than ((Number)val).doubleValue() to ensure
129             //equality between comparint new Double( 6.4 / 3 ) and the jexl expression of 6.4 / 3
130             return new Double  (Double.parseDouble(String.valueOf(val)));
131         }
132 
133         throw new Exception  ("Double coercion exception");
134     }
135 
136     /**
137      * Is Object a floating point number.
138      *
139      * @param o Object to be analyzed.
140      * @return true if it is a Float or a Double.
141      */
142     public static boolean isFloatingPoint(final Object   o) {
143         return o instanceof Float   || o instanceof Double  ;
144     }
145 
146     /**
147      * Is Object a whole number.
148      *
149      * @param o Object to be analyzed.
150      * @return true if Integer, Long, Byte, Short or Character.
151      */
152     public static boolean isNumberable(final Object   o) {
153         return o instanceof Integer  
154             || o instanceof Long  
155             || o instanceof Byte  
156             || o instanceof Short  
157             || o instanceof Character  ;
158     }
159 
160 }
161
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