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commit e9646012d3a0cb8b742e36a9314700deeea95a85 Author: Andy Seaborne <[email protected]> AuthorDate: Mon Jul 7 17:41:25 2025 +0100 Update ExProg2.java --- .../src/main/java/arq/examples/ExProg2.java | 151 ++++++++++----------- 1 file changed, 72 insertions(+), 79 deletions(-) diff --git a/jena-examples/src/main/java/arq/examples/ExProg2.java b/jena-examples/src/main/java/arq/examples/ExProg2.java index cf54fed371..c3a4b817ca 100644 --- a/jena-examples/src/main/java/arq/examples/ExProg2.java +++ b/jena-examples/src/main/java/arq/examples/ExProg2.java @@ -20,101 +20,94 @@ package arq.examples; // The ARQ application API. -import org.apache.jena.atlas.io.IndentedWriter ; -import org.apache.jena.graph.Triple ; -import org.apache.jena.query.* ; -import org.apache.jena.rdf.model.* ; -import org.apache.jena.sparql.core.Var ; -import org.apache.jena.sparql.expr.E_Regex ; -import org.apache.jena.sparql.expr.Expr ; -import org.apache.jena.sparql.expr.ExprVar ; -import org.apache.jena.sparql.syntax.ElementFilter ; -import org.apache.jena.sparql.syntax.ElementGroup ; -import org.apache.jena.vocabulary.DC ; +import org.apache.jena.atlas.io.IndentedWriter; +import org.apache.jena.graph.Triple; +import org.apache.jena.query.*; +import org.apache.jena.rdf.model.*; +import org.apache.jena.sparql.core.Var; +import org.apache.jena.sparql.expr.E_Regex; +import org.apache.jena.sparql.expr.Expr; +import org.apache.jena.sparql.expr.ExprVar; +import org.apache.jena.sparql.syntax.ElementFilter; +import org.apache.jena.sparql.syntax.ElementGroup; +import org.apache.jena.vocabulary.DC; /** Example : Build a query with a filter programmatically. * Note: it is often better to build and execute an algebra expression. See other examples. */ public class ExProg2 { - static public final String NL = System.getProperty("line.separator") ; - - public static void main(String[] args) - { - Model model = createModel() ; - - Query query = QueryFactory.make() ; - query.setQuerySelectType() ; - + static public final String NL = System.getProperty("line.separator"); + + public static void main(String[] args) { + Model model = createModel(); + + Query query = QueryFactory.make(); + query.setQuerySelectType(); + // See also ExProg1 - - ElementGroup elg = new ElementGroup() ; - - Var varTitle = Var.alloc("title") ; - Var varX = Var.alloc("x") ; - - Triple t1 = Triple.create(varX, DC.title.asNode(), varTitle) ; - elg.addTriplePattern(t1) ; - - // Adds a filter. Need to wrap variable in a NodeVar. - Expr expr = new E_Regex(new ExprVar(varTitle), "sparql", "i") ; - ElementFilter filter = new ElementFilter(expr) ; - elg.addElementFilter(filter) ; - - // Attach the group to query. - query.setQueryPattern(elg) ; - + + ElementGroup elg = new ElementGroup(); + + Var varTitle = Var.alloc("title"); + Var varX = Var.alloc("x"); + + Triple t1 = Triple.create(varX, DC.title.asNode(), varTitle); + elg.addTriplePattern(t1); + + // Adds a filter. Need to wrap variable in a NodeVar. + Expr expr = new E_Regex(new ExprVar(varTitle), "sparql", "i"); + ElementFilter filter = new ElementFilter(expr); + elg.addElement(filter); + + // Attach the group to query. + query.setQueryPattern(elg); + // Choose what we want - SELECT ?title - query.addResultVar(varTitle) ; - + query.addResultVar(varTitle); + // Print query with line numbers // Prefix mapping just helps serialization - query.getPrefixMapping().setNsPrefix("dc" , DC.getURI()) ; - query.serialize(new IndentedWriter(System.out,true)) ; - System.out.println() ; - - try(QueryExecution qexec = QueryExecutionFactory.create(query, model)) { + query.getPrefixMapping().setNsPrefix("dc", DC.getURI()); + query.serialize(new IndentedWriter(System.out, true)); + System.out.println(); + + try (QueryExecution qexec = QueryExecutionFactory.create(query, model)) { // Assumption: it's a SELECT query. - ResultSet rs = qexec.execSelect() ; - + ResultSet rs = qexec.execSelect(); + // The order of results is undefined. - System.out.println("Titles: ") ; - for ( ; rs.hasNext() ; ) - { - QuerySolution rb = rs.nextSolution() ; - + System.out.println("Titles: "); + for ( ; rs.hasNext() ; ) { + QuerySolution rb = rs.nextSolution(); + // Get title - variable names do not include the '?' (or '$') - RDFNode x = rb.get("title") ; - + RDFNode x = rb.get("title"); + // Check the type of the result value - if ( x instanceof Literal ) - { - Literal titleStr = (Literal)x ; - System.out.println(" "+titleStr) ; - } - else - System.out.println("Strange - not a literal: "+x) ; - + if ( x instanceof Literal ) { + Literal titleStr = (Literal)x; + System.out.println(" " + titleStr); + } else + System.out.println("Strange - not a literal: " + x); + } } } - - public static Model createModel() - { - Model model = ModelFactory.createDefaultModel() ; - - Resource r1 = model.createResource("http://example.org/book#1";) ; - Resource r2 = model.createResource("http://example.org/book#2";) ; - Resource r3 = model.createResource("http://example.org/book#3";) ; - - r1.addProperty(DC.title, "SPARQL - the book") - .addProperty(DC.description, "A book about SPARQL") ; - - r2.addProperty(DC.title, "Advanced techniques for SPARQL") ; - - r3.addProperty(DC.title, "Jena - an RDF framework for Java") - .addProperty(DC.description, "A book about Jena") ; - - return model ; + + public static Model createModel() { + Model model = ModelFactory.createDefaultModel(); + + Resource r1 = model.createResource("http://example.org/book#1";); + Resource r2 = model.createResource("http://example.org/book#2";); + Resource r3 = model.createResource("http://example.org/book#3";); + + r1.addProperty(DC.title, "SPARQL - the book").addProperty(DC.description, "A book about SPARQL"); + + r2.addProperty(DC.title, "Advanced techniques for SPARQL"); + + r3.addProperty(DC.title, "Jena - an RDF framework for Java").addProperty(DC.description, "A book about Jena"); + + return model; } }
