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49 package org.jaxen.function;
50
51 import java.util.List;
52
53 import org.jaxen.Context;
54 import org.jaxen.Function;
55 import org.jaxen.FunctionCallException;
56 import org.jaxen.Navigator;
57
58 /***
59 * <p><b>4.2</b> <code><i>string</i> substring-before(<i>string</i>,<i>string</i>)</code></p>
60 *
61 *
62 * <blockquote src="http://www.w3.org/TR/xpath#function-substring-before">
63 * The substring-before function returns the substring of the first argument
64 * string that precedes the first occurrence of the second argument string
65 * in the first argument string, or the empty string if the
66 * first argument string does not contain the second argument string.
67 * For example, substring-before("1999/04/01","/") returns 1999.
68 * </blockquote>
69 *
70 * @author bob mcwhirter (bob @ werken.com)
71 *
72 * @see <a href="http://www.w3.org/TR/xpath#function-substring-before" target="_top">Section 4.2 of the XPath Specification</a>
73 */
74 public class SubstringBeforeFunction implements Function
75 {
76
77
78 /***
79 * Create a new <code>SubstringBeforeFunction</code> object.
80 */
81 public SubstringBeforeFunction() {}
82
83
84 /***
85 * Returns the part of the string-value of the first item in <code>args</code>
86 * that comes before the string-value of the second item in <code>args</code>;
87 * or the empty string if the second string is not a substring of the first string.
88 *
89 * @param context the context at the point in the
90 * expression when the function is called
91 * @param args a list that contains two items
92 *
93 * @return a <code>String</code> containing that
94 * part of the string-value of the first item in <code>args</code>
95 * that comes before the string-value of the second item in <code>args</code>
96 *
97 * @throws FunctionCallException if <code>args</code> does not have length two
98 */
99 public Object call(Context context,
100 List args) throws FunctionCallException
101 {
102 if (args.size() == 2)
103 {
104 return evaluate( args.get(0),
105 args.get(1),
106 context.getNavigator() );
107 }
108
109 throw new FunctionCallException( "substring-before() requires two arguments." );
110 }
111
112 /***
113 * Returns the part of <code>strArg</code> that precedes the first occurence
114 * of <code>matchArg</code>; or the empty string if the
115 * <code>strArg</code> does not contain <code>matchArg</code>
116 *
117 * @param strArg the string from which the substring is extracted
118 * @param matchArg the string that marks the boundary of the substring
119 * @param nav the <code>Navigator</code> used to calculate the string-values of
120 * the first two arguments
121 *
122 * @return a <code>String</code> containing the part of <code>strArg</code> that precedes the first occurence
123 * of <code>matchArg</code>
124 *
125 */
126 public static String evaluate(Object strArg,
127 Object matchArg,
128 Navigator nav)
129 {
130 String str = StringFunction.evaluate( strArg,
131 nav );
132
133 String match = StringFunction.evaluate( matchArg,
134 nav );
135
136 int loc = str.indexOf(match);
137
138 if ( loc < 0 )
139 {
140 return "";
141 }
142
143 return str.substring(0, loc);
144
145 }
146 }