Query Builder for Jena. Implementations of Ask, Construct and Select builders that allow developers to create queries without resorting to StringBuilders or similar solutions.
Each of the builders has a series of methods to define the query. Each method returns the builder for easy chaing. The example:
SelectBuilder sb = new SelectBuilder() .addVar( "*" ) .addWhere( "?s", "?o", "?p" ); Query q = sb.build();
produces SELECT * WHERE { ?s ?o ?p . }
In addition to making it easier to build valid queries the QueryBuilder has a clone method. Using this a developer can create as “Template” query and add to it as necessary.
for example using the above query as the “template” the this code:
SelectBuilder sb2 = sb.clone(); sb2.addPrefix( "foaf", "http://xmlns.com/foaf/0.1/" ).addWhere( ?s, RDF.type, foaf:Person)
produces PREFIX foaf: http://xmlns.com/foaf/0.1/ SELECT * WHERE { ?s ?o ?p . ?s <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> foaf:person . }
The query builders have the ability to replace variables with other values. This can be
SelectBuilder sb = new SelectBuilder() .addVar( "*" ) .addWhere( "?s", "?o", "?p" ); sb.setVar( Var.alloc( "?p" ), NodeFactory.createURI( "http://xmlns.com/foaf/0.1/Person" ) Query q = sb.build();
produces SELECT * WHERE { ?s ?o <http://xmlns.com/foaf/0.1/Person> . }