1 package org.apache.xmlbeans.impl.xpathgen;
2
3 import org.apache.xmlbeans.XmlCursor;
4 import org.apache.xmlbeans.XmlCursor.TokenType;
5
6 import javax.xml.namespace.QName;
7 import javax.xml.namespace.NamespaceContext;
8
9 /**
10 * Generates an XPath String that points to a given position in an XML document
11 */
12 public class XPathGenerator
13 {
14 /**
15 * Generates an XPath pointing to the position in the document indicated by <code>node</code>.
16 * <p>If the <code>context</code> parameter is null, the XPath is absolute, otherwise the
17 * XPath will be relative to the position indicated by <code>context</code>.</p>
18 * <p>Note: the cursor position for the <code>node</code> parameter is not preserved</p>
19 * @param node the position in the document that the generated path will point to
20 * @param context the context node; the generated path will be relative to it if not null and if
21 * pointing to an element on the path from the document root to <code>node</code>
22 * @param nsctx a namespace context that will be used to obtain prefixes; a (non-default)
23 * namespace mapping must be available for all required namespace URIs
24 * @return the generated path as a <code>String</code>
25 * @throws XPathGenerationException if the path could not be generated: the cursor is in a bad
26 * position (like over a comment) or no prefix mapping was found for one of the namespace URIs
27 */
28 public static String generateXPath(XmlCursor node, XmlCursor context, NamespaceContext nsctx)
29 throws XPathGenerationException
30 {
31 if (node == null)
32 throw new IllegalArgumentException("Null node");
33 if (nsctx == null)
34 throw new IllegalArgumentException("Null namespace context");
35 TokenType tt = node.currentTokenType();
36 if (context != null && node.isAtSamePositionAs(context))
37 return ".";
38 switch (tt.intValue())
39 {
40 case TokenType.INT_ATTR:
41 QName name = node.getName();
42 node.toParent();
43 String pathToParent = generateInternal(node, context, nsctx);
44 return pathToParent + '/' + '@' + qnameToString(name, nsctx);
45 case TokenType.INT_NAMESPACE:
46 name = node.getName();
47 node.toParent();
48 pathToParent = generateInternal(node, context, nsctx);
49 String prefix = name.getLocalPart();
50 if (prefix.length() == 0)
51 return pathToParent + "/@xmlns";
52 else
53 return pathToParent + "/@xmlns:" + prefix;
54 case TokenType.INT_START:
55 case TokenType.INT_STARTDOC:
56 return generateInternal(node, context, nsctx);
57 case TokenType.INT_TEXT:
58 int nrOfTextTokens = countTextTokens(node);
59 node.toParent();
60 pathToParent = generateInternal(node, context, nsctx);
61 if (nrOfTextTokens == 0)
62 return pathToParent + "/text()";
63 else
64 return pathToParent + "/text()[position()=" + nrOfTextTokens + ']';
65 default:
66 throw new XPathGenerationException("Cannot generate XPath for cursor position: " +
67 tt.toString());
68 }
69 }
70
71 private static String generateInternal(XmlCursor node, XmlCursor context, NamespaceContext nsctx)
72 throws XPathGenerationException
73 {
74 if (node.isStartdoc())
75 return "";
76 if (context != null && node.isAtSamePositionAs(context))
77 return ".";
78 assert node.isStart();
79 QName name = node.getName();
80 XmlCursor d = node.newCursor();
81 if (!node.toParent())
82 return "/" + name;
83 int elemIndex = 0, i = 1;
84 node.push();
85 if (!node.toChild(name))
86 throw new IllegalStateException("Must have at least one child with name: " + name);
87 do
88 {
89 if (node.isAtSamePositionAs(d))
90 elemIndex = i;
91 else
92 i++;
93 } while (node.toNextSibling(name));
94 node.pop();
95 d.dispose();
96 String pathToParent = generateInternal(node, context, nsctx);
97 return i == 1 ? pathToParent + '/' + qnameToString(name, nsctx) :
98 pathToParent + '/' + qnameToString(name, nsctx) + '[' + elemIndex + ']';
99 }
100
101 private static String qnameToString(QName qname, NamespaceContext ctx)
102 throws XPathGenerationException
103 {
104 String localName = qname.getLocalPart();
105 String uri = qname.getNamespaceURI();
106 if (uri.length() == 0)
107 return localName;
108 String prefix = qname.getPrefix();
109 if (prefix != null && prefix.length() > 0)
110 {
111 // Try to use the same prefix if it maps to the right URI
112 String mappedUri = ctx.getNamespaceURI(prefix);
113 if (uri.equals(mappedUri))
114 return prefix + ':' + localName;
115 }
116 // The prefix is not specified, or it is not mapped to the right URI
117 prefix = ctx.getPrefix(uri);
118 if (prefix == null)
119 throw new XPathGenerationException("Could not obtain a prefix for URI: " + uri);
120 if (prefix.length() == 0)
121 throw new XPathGenerationException("Can not use default prefix in XPath for URI: " + uri);
122 return prefix + ':' + localName;
123 }
124
125 /**
126 * Computes how many text nodes the
127 * @param c the position in the document
128 * @return how many text nodes occur before the position determined by <code>c</code>
129 */
130 private static int countTextTokens(XmlCursor c)
131 {
132 int k = 0;
133 int l = 0;
134 XmlCursor d = c.newCursor();
135 c.push();
136 c.toParent();
137 TokenType tt = c.toFirstContentToken();
138 while (!tt.isEnd())
139 {
140 if (tt.isText())
141 {
142 if (c.comparePosition(d) > 0)
143 // We have moved after the initial position
144 l++;
145 else
146 k++;
147 }
148 else if (tt.isStart())
149 c.toEndToken();
150 tt = c.toNextToken();
151 }
152 c.pop();
153 return l == 0 ? 0 : k;
154 }
155
156 public static void main(String[] args) throws org.apache.xmlbeans.XmlException
157 {
158 String xml =
159 "<root>\n" +
160 "<ns:a xmlns:ns=\"http://a.com\"><b foo=\"value\">text1<c/>text2<c/>text3<c>text</c>text4</b></ns:a>\n" +
161 "</root>";
162 NamespaceContext ns = new NamespaceContext() {
163 public String getNamespaceURI(String prefix)
164 {
165 if ("ns".equals(prefix))
166 return "http://a.com";
167 else
168 return null;
169 }
170 public String getPrefix(String namespaceUri)
171 {
172 return null;
173 }
174 public java.util.Iterator getPrefixes(String namespaceUri)
175 {
176 return null;
177 }
178 };
179 XmlCursor c = org.apache.xmlbeans.XmlObject.Factory.parse(xml).newCursor();
180 c.toFirstContentToken(); // on <root>
181 c.toFirstContentToken(); // on <a>
182 c.toFirstChild(); // on <b>
183 c.toFirstChild(); // on <c>
184 c.push(); System.out.println(generateXPath(c, null, ns)); c.pop();
185 c.toNextSibling();
186 c.toNextSibling(); // on the last <c>
187 c.push(); System.out.println(generateXPath(c, null, ns)); c.pop();
188 XmlCursor d = c.newCursor();
189 d.toParent();
190 c.push(); System.out.println(generateXPath(c, d, ns)); c.pop();
191 d.toParent();
192 c.push(); System.out.println(generateXPath(c, d, ns)); c.pop();
193 c.toFirstContentToken(); // on text content of the last <c>
194 c.push(); System.out.println(generateXPath(c, d, ns)); c.pop();
195 c.toParent();
196 c.toPrevToken(); // on text content before the last <c>
197 c.push(); System.out.println(generateXPath(c, d, ns)); c.pop();
198 c.toParent(); // on <b>
199 c.push(); System.out.println(generateXPath(c, d, ns)); c.pop();
200 c.toFirstAttribute(); // on the "foo" attribute
201 c.push(); System.out.println(generateXPath(c, d, ns)); c.pop();
202 c.toParent();
203 c.toParent();
204 c.toNextToken(); // on the "xmlns:ns" attribute
205 c.push(); System.out.println(generateXPath(c, d, ns)); c.pop();
206 c.push(); System.out.println(generateXPath(c, null, ns)); c.pop();
207 }
208 }