net.sf.saxon.xpath.JAXPVariable Maven / Gradle / Ivy
package net.sf.saxon.xpath;
import net.sf.saxon.expr.Binding;
import net.sf.saxon.expr.BindingReference;
import net.sf.saxon.expr.VariableDeclaration;
import net.sf.saxon.expr.XPathContext;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.value.*;
import net.sf.saxon.om.ValueRepresentation;
import net.sf.saxon.om.StructuredQName;
import javax.xml.namespace.QName;
import javax.xml.xpath.XPathVariableResolver;
/**
* An object representing an XPath variable for use in the JAXP XPath API. The object
* is created at compile time when the parser tries to bind a variable reference; the
* value is fetched at run-time from the XPathVariableResolver. With this interface,
* there is no way of reporting a static error if the variable has not been declared.
*
* In Saxon terms, this class is both a VariableDeclaration and a Binding. Unlike
* a normal VariableDeclaration, it isn't created in advance, but is created on demand
* when the parser encounters a variable reference. This actually means that if the
* XPath expression contains two references to the same variable, two VariableDeclarations
* will be created; however, they will be indistinguishable to the VariableResolver.
* Acting as a VariableDeclaration, the object goes through the motions of fixing up
* a binding to a variable reference (in practice, of course, there is exactly one
* reference to the variable). Acting as a run-time binding, it then evaluates the
* variable by calling the XPathVariableResolver supplied by the API caller. If no
* XPathVariableResolver was supplied, an error is reported when a variable is encountered;
* but if the variable resolver doesn't recognize the variable name, it returns null,
* which is treated as an empty sequence.
*
*/
public final class JAXPVariable implements VariableDeclaration, Binding {
private StructuredQName name;
private XPathVariableResolver resolver;
/**
* Private constructor: for use only be the protected factory method make()
* @param name the name of the variable
* @param resolver the resolver used in conjunction with this variable
*/
protected JAXPVariable(StructuredQName name, XPathVariableResolver resolver) {
this.name = name;
this.resolver = resolver;
}
public SequenceType getRequiredType() {
return SequenceType.ANY_SEQUENCE;
}
/**
* Indicate whether the binding is local or global. A global binding is one that has a fixed
* value for the life of a query or transformation; any other binding is local.
*/
public boolean isGlobal() {
return true;
}
/**
* Test whether it is permitted to assign to the variable using the saxon:assign
* extension element. This will only be for an XSLT global variable where the extra
* attribute saxon:assignable="yes" is present.
*/
public final boolean isAssignable() {
return false;
}
/**
* If this is a local variable held on the local stack frame, return the corresponding slot number.
* In other cases, return -1.
*/
public int getLocalSlotNumber() {
return -1;
}
/**
* Get the name of the variable as a structured QName
*/
public StructuredQName getVariableQName() {
return name;
}
/**
* Method called by the XPath expression parser to register a reference to this variable.
* This method should not be called by users of the API.
*/
public void registerReference(BindingReference ref) {
ref.setStaticType(SequenceType.ANY_SEQUENCE, null, 0);
ref.fixup(this);
}
/**
* Get the value of the variable. This method is used by the XPath execution engine
* to retrieve the value.
* @param context The dynamic evaluation context
* @return The value of the variable
*/
public ValueRepresentation evaluateVariable(XPathContext context) throws XPathException {
Object value = resolver.resolveVariable(
(QName)name.makeQName(context.getConfiguration()));
if (value == null) {
return EmptySequence.getInstance();
}
return Value.convertJavaObjectToXPath(
value, SequenceType.ANY_SEQUENCE, context);
}
/**
* Construct a JAXP QName from a Saxon QNameValue
* @param in the Saxon QNameValue
* @return the JAXP QName
*/
QName makeQName(QNameValue in) {
return new QName(in.getNamespaceURI(), in.getLocalName(), in.getPrefix());
}
}
//
// The contents of this file are subject to the Mozilla Public License Version 1.0 (the "License");
// you may not use this file except in compliance with the License. You may obtain a copy of the
// License at http://www.mozilla.org/MPL/
//
// Software distributed under the License is distributed on an "AS IS" basis,
// WITHOUT WARRANTY OF ANY KIND, either express or implied.
// See the License for the specific language governing rights and limitations under the License.
//
// The Original Code is: all this file.
//
// The Initial Developer of the Original Code is Michael H. Kay
//
// Portions created by (your name) are Copyright (C) (your legal entity). All Rights Reserved.
//
// Contributor(s): none.
//