using conditions in XPath expressions
I need to parse through an XML document in the database and search for a given expression in it. Then, I must return a String value if the given expression is present in the XML else I need to parse through the next expression and return another String value and so on.
I achieved this by using the following code:
// An xml document is passed as a Node when getEntryType() method is called
public static class XMLTextFields {
public static String getEntryType(Node target) throws XPathExpressionException {
XPathFactory factory = XPathFactory.newInstance();
XPath xpath = factory.newXpath();
String entryType = null;
String [] expression = new String [] {"./libx:package", "./libx:libapp", "./libx:module"};
String [] type = new String [] {"Package", "Libapp", "Module" };
for (int i = 0; i < 3; i ++) {
XPathExpression expr = xpath.compile(expression[i]);
Object result = expr.evaluate(target, XPathConstants.NODESET);
NodeList nodes = (NodeList) result;
if (nodes.getLength() == 0)
continue;
entryType = (type[i]);
}
开发者_Python百科 return entryType;
}
}
I am wondering if there is a simpler way to do this? Meaning, is there a way to use the "expression" like a function which returns a string if the expression is present in the xml.
I am guessing I should be able to do something like this but am not exactly sure:
String [] Expression = new String [] {"[./libx:package]\"Package\"", ....}
Meaning, return "Package" if libx:package node exists in the given XML
If your XPath processor is version 2, you can use if expressions: http://www.w3.org/TR/xpath20/#id-conditionals .
You can use XSLT here. In XSLT you can check the node name by using
<xsl:value-of select="*[starts-with(name(),'libx:package')]" />
OR you can check using
<xsl:if select="name()='libx:package'" >
<!-- Your cusotm elements here... -->
</xsl:if>
You can check existence of Element OR Attribute this way to validate specific needs.
hope this helps.
Yes there is, just use an XPath functions in your expression:
Expression exp = xpath.compile("local-name(*[local-name() = 'package'])")
// will return "package" for any matching elements
exp.evaluate(target, XPathConstants.STRING);
But this will return "package" instead of "Package". Note the capital P
Below is the Test code:
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpression;
import javax.xml.xpath.XPathExpressionException;
import javax.xml.xpath.XPathFactory;
import org.w3c.dom.Document;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import java.util.Map;
import java.util.HashMap;
public class Test {
private static Map<String, String> mappings = new HashMap<String, String>();
static {
mappings.put("package", "Package");
mappings.put("libapp", "Application");
mappings.put("module", "Module");
}
public static void main(String[] args) throws Throwable {
XPathFactory factory = XPathFactory.newInstance();
XPath xpath = factory.newXPath();
String entryType = null;
XPathExpression [] expressions = new XPathExpression[] {
xpath.compile("local-name(*[local-name() = 'package'])"),
xpath.compile("local-name(*[local-name() = 'libapp'])"),
xpath.compile("local-name(*[local-name() = 'module'])")
};
DocumentBuilderFactory fac = DocumentBuilderFactory.newInstance();
DocumentBuilder parser = fac.newDocumentBuilder();
Document doc = parser.parse(args[0]);
for(int i = 0; i < expressions.length; i++) {
String found = (String) expressions[i].evaluate(doc.getDocumentElement(),
XPathConstants.STRING);
entryType = mappings.get(found);
if(entryType != null && !entryType.trim().isEmpty()) {
break;
}
}
System.out.println(entryType);
}
}
Contents of text file:
<?xml version="1.0"?>
<root xmlns:libx="urn:libex">
<libx:package>mypack</libx:package>
<libx:libapp>myapp</libx:libapp>
<libx:module>mymod</libx:module>
</root>
In XPath 1.0
concat(translate(substring(local-name(libx:package|libx:libapp|libx:module),
1,
1),
'plm',
'PLM'),
substring(local-name(libx:package|libx:libapp|libx:module),2))
EDIT: It was dificult to understand the path because there was not provided input sample...
@ALL: Thanks!
I used:
XPathExpression expr = xpath.compile("concat(substring('Package',0,100*boolean(//libx:package))," + "substring('Libapp',0,100*boolean(//libx:libapp)),substring('Module',0,100*boolean(//libx:module)))"); expr.evaluate(target, XPathConstants.STRING);
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