Saxon

Legacy ID: #4525373 Legacy Poster: Jocelyn Raymond (jraymond67)

Hi, I am trying to understand how some of the Saxon Java API works. We have purchased saxon-8.9.0.4 which I believe is the latest release. I have gone through the saxon-resources java examples to learn more about how to use the API. ---------------------- What I am trying to do ---------------------- I want to create an xml data object in java which would contain methods to modify and query the data model. I do understand that using the TinyTree Model we cannot "update" the tree. So what I have been trying to exploit is the following snippet (full code further below): TinyBuilder builder = new TinyBuilder(); XQueryExpression exp = this.sqc.compileQuery(xquery); // where sqc is a StaticQueryContext DynamicQueryContext dqc = new DynamicQueryContext(this.config); // this.config is a "new" Configuration that was instantiated during construction. dqc.setContextItem(this.doc) // this.doc is a NodeInfo see constructor below exp.run(dqc,builder,new Properties()); this.doc = builder.getCurrentRoot(); // Once I assign a new TinyTree, other Xquery do not work anymore (see error below) Hopefully, you will see that what I want to do is to keep an TinyTree as the model for the data. The data model can be "modified" by simply re-building the TinyTree using XQuery and even transform. This data object is passed through several process that can query and modify the data along the way. I only want to "serialize" at the end of my system which is why I would like to keep the model as a Tree and not a String. Hopefully, I am making some sense :-) Please let me know if this is a crazy idea or if there is a simpler method to do this. ---------------------- Error message: ---------------------- update done Error on line 1 of module with no systemId: XPDY0050: The root of the tree containing the context item is not a document node The root of the tree containing the context item is not a document node ; SystemID: module with no systemId; Line#: 1; Column#: -1 net.sf.saxon.trans.DynamicError: The root of the tree containing the context item is not a document node at net.sf.saxon.expr.Expression.dynamicError(Expression.java:780) at net.sf.saxon.expr.RootExpression.getNode(RootExpression.java:73) at net.sf.saxon.expr.SingleNodeExpression.iterate(SingleNodeExpression.java:113) at net.sf.saxon.expr.PathExpression.iterate(PathExpression.java:826) at net.sf.saxon.expr.Expression.process(Expression.java:346) at net.sf.saxon.query.XQueryExpression.run(XQueryExpression.java:346) at ca.ualberta.registrar.data.XMLData.applyXQuery(Unknown Source) at ca.ualberta.registrar.data.XMLData.serialize(Unknown Source) at ca.ualberta.registrar.data.XMLData.main(Unknown Source) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.apache.tools.ant.taskdefs.ExecuteJava.run(ExecuteJava.java:193) at org.apache.tools.ant.taskdefs.ExecuteJava.execute(ExecuteJava.java:130) at org.apache.tools.ant.taskdefs.Java.run(Java.java:705) at org.apache.tools.ant.taskdefs.Java.executeJava(Java.java:177) at org.apache.tools.ant.taskdefs.Java.execute(Java.java:83) at org.apache.tools.ant.UnknownElement.execute(UnknownElement.java:275) at org.apache.tools.ant.Task.perform(Task.java:364) at org.apache.tools.ant.Target.execute(Target.java:341) at org.apache.tools.ant.Target.performTasks(Target.java:369) at org.apache.tools.ant.Project.executeTarget(Project.java:1214) at org.apache.tools.ant.Project.executeTargets(Project.java:1062) at org.apache.tools.ant.Main.runBuild(Main.java:673) at org.apache.tools.ant.Main.startAnt(Main.java:188) at org.apache.tools.ant.Main.start(Main.java:151) at org.apache.tools.ant.Main.main(Main.java:241) -------------------------------------- Here is the code for the entire class: // packages and import were left out -------------------------------------- Look at the main method to see the test of this data object. Running the main method gives the error shown above. public class XMLData { public static final net.sf.saxon.TransformerFactoryImpl factory = new net.sf.saxon.TransformerFactoryImpl(); // We are Saxon specific private Configuration config = new Configuration(); // as long this object is alive, we will use one configuration object. private NodeInfo doc = null; private StaticQueryContext sqc = null; public static final String OMIT_XML_DECLARATION_Yes = "yes"; public static final String OMIT_XML_DECLARATION_No = "no"; // C O N S T R U C T O R S private XMLData(){}; // we do not want empty xml data model. // @XMLData(String xml) // We can construct an XMLData based on a xml string. public XMLData(String xml) throws Exception { this.sqc = new StaticQueryContext(this.config); this.doc = this.config.buildDocument(new StreamSource(new StringReader(xml))); } // @serialize // Simply output a String representation of the xml model i.e. the string will contain tags and all. public String serialize(String omitXmlDeclaration) throws Exception { return this.applyXQuery("/node()", omitXmlDeclaration); } // @transform // applies a transformation on the current xml model. The current xml model is replaced with the result of the transformation. public void transform(Transformer transformer) throws Exception { } // @applyXPath // applies the xpath expression on the current xml model. A String value which is the concatenation of all TextNode is returned. // The current xml data model should not be modified. public String applyXPath(String xpath) throws Exception { return null; } // @applyXQuery // applies the xquery expression on the current xml model and the "xml" result is returned as a String. // The current xml data model should not be modified. // Yes assume that the xquery will result into another xml structure. public String applyXQuery(String xquery, String omitXmlDeclaration) throws Exception { ByteArrayOutputStream baos = new ByteArrayOutputStream(); final XQueryExpression exp = this.sqc.compileQuery(xquery); final DynamicQueryContext dqc = new DynamicQueryContext(this.config); final Properties props = new Properties(); props.setProperty(OutputKeys.METHOD, "xml"); props.setProperty(OutputKeys.INDENT, "no"); props.setProperty(OutputKeys.OMIT_XML_DECLARATION, (omitXmlDeclaration.equals(XMLData.OMIT_XML_DECLARATION_Yes) ? "yes" : "no")); dqc.setContextItem(this.doc); exp.run(dqc, new StreamResult(baos),props); return baos.toString(); } // @updateUsingXquery // The result of the xquery is used to re-build the current model i.e. re-build a TinyTree. public void updateUsingXQuery(String xquery) throws Exception { TinyBuilder builder = new TinyBuilder(); final XQueryExpression exp = this.sqc.compileQuery(xquery); final DynamicQueryContext dqc = new DynamicQueryContext(this.config); final Properties props = new Properties(); props.setProperty(OutputKeys.METHOD, "xml"); props.setProperty(OutputKeys.INDENT, "no"); dqc.setContextItem(this.doc); exp.run(dqc,builder,props); this.doc = builder.getCurrentRoot(); } public static void main(String args[]){ try{ String xml = "<?xml version='1.0'?><person><name><firstname>Homer</firstname><lastname>Simpson</lastname></name><gender>M</gender><birthdate>2000-01-25</birthdate></person>"; XMLData person = new XMLData(xml); String xquery = "for $doc in /node() return <person><name><firstname>OJ</firstname><lastname>Samson</lastname></name>{$doc/gender}{$doc/birthdate}</person>"; person.updateUsingXQuery(xquery); System.out.println("update done"); System.out.println(person.serialize(XMLData.OMIT_XML_DECLARATION_No)); }catch (Exception ex){ System.out.println(ex.getMessage()); ex.printStackTrace(); } } }