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63 package org.jaxen.function;
64
65 import java.util.List;
66
67 import org.jaxen.Context;
68 import org.jaxen.Function;
69 import org.jaxen.FunctionCallException;
70 import org.jaxen.Navigator;
71
72 /***
73 * <p><b>4.2</b> <code><i>string</i> substring-before(<i>string</i>,<i>string</i>)</code></p>
74 *
75 *
76 * <blockquote src="http://www.w3.org/TR/xpath#function-substring-before">
77 * The substring-before function returns the substring of the first argument
78 * string that precedes the first occurrence of the second argument string
79 * in the first argument string, or the empty string if the
80 * first argument string does not contain the second argument string.
81 * For example, substring-before("1999/04/01","/") returns 1999.
82 * </blockquote>
83 *
84 * @author bob mcwhirter (bob @ werken.com)
85 *
86 * @see <a href="http://www.w3.org/TR/xpath#function-substring-before" target="_top">Section 4.2 of the XPath Specification</a>
87 */
88 public class SubstringBeforeFunction implements Function
89 {
90
91
92 /***
93 * Create a new <code>SubstringBeforeFunction</code> object.
94 */
95 public SubstringBeforeFunction() {}
96
97
98 /***
99 * Returns the part of the string-value of the first item in <code>args</code>
100 * that comes before the string-value of the second item in <code>args</code>;
101 * or the empty string if the second string is not a substring of the first string.
102 *
103 * @param context the context at the point in the
104 * expression when the function is called
105 * @param args a list that contains two items
106 *
107 * @return a <code>String</code> containing that
108 * part of the string-value of the first item in <code>args</code>
109 * that comes before the string-value of the second item in <code>args</code>
110 *
111 * @throws FunctionCallException if <code>args</code> does not have length two
112 */
113 public Object call(Context context,
114 List args) throws FunctionCallException
115 {
116 if (args.size() == 2)
117 {
118 return evaluate( args.get(0),
119 args.get(1),
120 context.getNavigator() );
121 }
122
123 throw new FunctionCallException( "substring-before() requires two arguments." );
124 }
125
126 /***
127 * Returns the part of <code>strArg</code> that precedes the first occurence
128 * of <code>matchArg</code>; or the empty string if the
129 * <code>strArg</code> does not contain <code>matchArg</code>
130 *
131 * @param strArg the string from which the substring is extracted
132 * @param matchArg the string that marks the boundary of the substring
133 * @param nav the <code>Navigator</code> used to calculate the string-values of
134 * the first two arguments
135 *
136 * @return a <code>String</code> containing the part of <code>strArg</code> that precedes the first occurence
137 * of <code>matchArg</code>
138 *
139 */
140 public static String evaluate(Object strArg,
141 Object matchArg,
142 Navigator nav)
143 {
144 String str = StringFunction.evaluate( strArg,
145 nav );
146
147 String match = StringFunction.evaluate( matchArg,
148 nav );
149
150 int loc = str.indexOf(match);
151
152 if ( loc < 0 )
153 {
154 return "";
155 }
156
157 return str.substring(0, loc);
158
159 }
160 }