Working with Namespaces
Standard Namespaces
Namespaces class contains constants to many standard namespaces which we use in our daily projects.
import static jlibs.xml.Namespaces.*;
System.out.println(URI_SOAP);
System.out.println(URI_WSDL);
It can also suggest standard prefixes used for those namespaces.
String prefix = Namespaces.suggestPrefix(URI_WSDL);
System.out.println(prefix); // prints "wsdl"
Namespaces.getSuggested() returns java.util.Properties object where key is URI and value is suggested prefix;
MyNamespaceSupport
MyNamespaceSupport extends
org.xml.sax.helpers.NamespaceSupport to provide some handy features.
It is tedious to find prefix from org.xml.sax.helpers.NamespaceSupport. for example:
import org.xml.sax.helpers.NamespaceSupport;
NamespaceSupport nsSupport = new NamespaceSupport();
nsSupport.declarePrefix("ns1", "http://mynamespace1");
nsSupport.declarePrefix("", "http://mynamespace2");
// to find prefix of "http://mynamespace1"
System.out.println(nsSupport.getPrefix("http://mynamespace1")); // prints "ns1"
// let us try to find prefix of "http://mynamespace2"
System.out.println(nsSupport.getPrefix("http://mynamespace2")); // prints null, but we expect ""
As per javadoc, NamespaceSupport.getPrefix(...) returns prefixes only for those namespaces which are bound to non-empty prefix.
So in order to find prefix properly, we should do something like this:
``java
String prefix = nsSupport.getPrefix(uri);
if(prefix==null){
if(nsSupport.getURI(“”).equals(uri))
prefix = “”;
}
System.out.println(“prefix: “+prefix);
`MyNamespaceSupport` provides handy method `findPrefix(uri)` for this:
~~~java
import jlibs.xml.sax.helper.MyNamespaceSupport;
MyNamespaceSupport nsSupport = new MyNamespaceSupport();
nsSupport.declarePrefix("", "http://mynamespace2");
// let us try to find prefix of "http://mynamespace2"
System.out.println(nsSupport.findPrefix("http://mynamespace2")); // prints ""
It also helps you in suggesting prefixes:
String prefix = nsSupport.declarePrefix("http://www.google.com"); // we are asking to generate prefix
System.out.println(prefix); // prints "google"
You can also override the suggested prefix for any uri, as below:
nsSupport.suggestPrefix("tns", "http://java.sun.com"); // we are just suggesting (not declaring)
....
....
String prefix = nsSupport.declare("http://java.sun.com");
System.out.println(prefix); // prints "tns"
DefaultNamespaceContext
JAXP provides interface org.xml.sax.helpers.NamespaceContext interface, but doesn’t provide any concrete implementation for this.
This interface is used to pass namespace and prefix binding for xpath evaluation (see javax.xml.xpath.XPath)
DefaultNamespaceContext implements this interface.
DefaultNamespaceContext nsContext = new DefaultNamespaceContext();
nsContext.declarePrefix("ns1", "http://namespace1");
String prefix = nsContext.declarePrefix("http://www.google.com"); // prefix will be suggested to "google"
// now we can use nsContext for xpath evaluation<br>
You can also create DefaultNamespaceContext from MyNamespaceSupport:
MyNamespaceSupport nsSupport = .....
......
DefaultNamespaceContext nsContext = new DefaultNamespaceContext(nsSupport);
ClarkName
ClarkName is String notation for javax.xml.namespaces.QName.
import jlibs.xml.ClarkName;
String str1 = ClarkName.valueOf("htpp://namespace1", "elem1"); // str1 will be "{http://namespace1}elem1"
String str2 = ClarkName.valueOf("", "elem2"); // str2 will be "elem1"
This is compatible with QName.toString()
you can get the namespace and local-name back:
String clarkName = ClarkName.valueOf("htpp://namespace1", "elem1");
String str[] = ClarkName.split(clarkName);
System.out.println(str[0]); // prints "http://namespace1"
System.out.println(str[2]); // prints "elem1"
support you want to save location of particular element in xpath form, for example:
ns1:elem1/ns2:elem2/ns2:elem3
where
ns1="http://namespace1"
ns2="http://namespace2"
ns3="http://namespace3"
you can convert into raw xpath by inlining namespaces into xpath:
{http://namespace1}elem1/{http://namespace2}elem2/{http://namespace1}elem3
this form will be easier to save to some file and restore it back; ClarkName provides handy method to split such paths.
String clarkPath = "{http://namespace1}elem1/{http://namespace2}elem2/{http://namespace1}elem3";
String clarkNames[] = ClarkName.splitPath(clarkPath);